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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Had a JTS radio mic receiver on the bench today. "No power", said the job
ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) Arfa |
#2
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Arfa Daily wrote:
Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) Arfa Or you could track down a Shortsqueek by Global Specialties Model SQ-1.Made in the 1970s and 80s it is a handy device to keep to track down shorts on PCBs. Using a small op-amp that changes pitch depending on how low the resistance is you can find shorts such as you describe fairly quickly as long as your ear is good for tone changes of a few Hertz. Polar Devices (UK) made Tone Ohm which was a similar device (I need a probe if anyone has a spare) that I haven't been able to test (because I'm missing the probe!). Here is the manual for Shortsqueek (470k PDF) http://www.flippers.com/pdfs/GlobalS...Model_SQ-1.pdf These turn up on eBay from time to time - I bought two for my shop and they do save hours of time (and chopping traces) every now and then... John :-#)# -- (Please post followups or tech enquiries to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
#3
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![]() Arfa Daily wrote: Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) I used to use a current limited power supply and a 4.5 digit voltmeter to track the voltage drop on power rails. You would see larger voltage drops till you reached the short, and smaller ones after that. I did this at the factor on boards that cost us $8000 in components to stuff, so I had to use non destructive testing. -- You can't have a sense of humor, if you have no sense. |
#4
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"Arfa Daily" wrote in
: Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) Arfa Ive done the same thing on TEK scopes. sometimes,I paralleled the current limit resistor on a supply with another R to increase the current output and see what smokes or pops. those glass axial ceramic caps would pop,the dipped tantalums would smoke. Sometimes,the scope would begin working,because the current limit was right at the hairy edge. I found a series pass XSTR with a bad B-E junction that way.It affected the current limit point. -- Jim Yanik jyanik at localnet dot com |
#5
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![]() "Arfa Daily" wrote in message ... Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. That method has located many S/C zeners for me. |
#6
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On Mon, 20 Feb 2012 17:38:14 -0000, "Arfa Daily"
put finger to keyboard and composed: On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. Nice work! - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#7
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![]() "Arfa Daily" Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) ** This is known as the " tune for maximum smoke " method. Often shows up short circuit bypass ceramics and regular pigtail tantalums too. How come you did not have the matching transmitter ?? I always insist on customers including them - more than once I have been given a mic and receiver pair that do not work because they are on different frequencies. ..... Phil |
#8
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Ian Field wrote in message
... "Arfa Daily" wrote in message ... Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. That method has located many S/C zeners for me. A non contact IR thermometer can be useful for such and similar low ohmic VTS , to wave over the errant board |
#9
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On Mon, 20 Feb 2012 17:38:14 -0000 "Arfa Daily"
wrote in Message id: : Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) You could also try using a good four wire DMM set to measure resistance. I use a Keithley 2000 which gives me resolution down to 100 micro-ohms. |
#10
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"Arfa Daily" wrote in message
... Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) Arfa I do this sometimes, but occasionally: a.) The short will burn itself open, or b.) The short is really zero point zero ohms and you start burning foil runs before any component reveals itself by getting hot. I might try the current limited method next time, but those very small voltage differences may be a problem. I don't own such a DC supply though, I'd have to use an actual resistor. Might also be a good excuse to buy a non-contact thermometer ;-) Mark Z. |
#11
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Mark Zacharias wrote in message
... "Arfa Daily" wrote in message ... Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) Arfa I do this sometimes, but occasionally: a.) The short will burn itself open, or b.) The short is really zero point zero ohms and you start burning foil runs before any component reveals itself by getting hot. I might try the current limited method next time, but those very small voltage differences may be a problem. I don't own such a DC supply though, I'd have to use an actual resistor. Might also be a good excuse to buy a non-contact thermometer ;-) Mark Z. I would recommend one, useful for zeroing in on failing caps in SMPS also, no probes anywhere near any HV. Use on the Fahrenheit scale for more resolution. Try along the wall of TVs in an electronics retail barn is quite an eye opener (makers never seem to specify electricity consumption so this is a good proxy). I'm surprised the cops don't dish them out to beat officers - much cheaper than flying FLIR choppers/planes to pick up skunk factories (another thing to try by walking along a street - noticeable variation in heat loss between brick & windows etc). |
#12
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![]() "Arfa Daily" wrote in message ... Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) Arfa Behringer 24 channel M8000 Eurodesks used to regularly come in with one of the 100's (if not 1000's) of 17v rail bypass capacitors shorted. I used to stick 5 amps from a bench supply down the offending rail, and it would disappear in a puff of smoke within 10 seconds. Although not strictly a pro repair, I always told the customer what I was going to do, how much it would cost, and how much it would cost if I had to dismantle the whole desk instead and conduct a proper search. Not one chose the dismantling route, funnily enough. Gareth. |
#13
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Gareth Magennis wrote in message
news ![]() "Arfa Daily" wrote in message ... Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) Arfa Behringer 24 channel M8000 Eurodesks used to regularly come in with one of the 100's (if not 1000's) of 17v rail bypass capacitors shorted. I used to stick 5 amps from a bench supply down the offending rail, and it would disappear in a puff of smoke within 10 seconds. Although not strictly a pro repair, I always told the customer what I was going to do, how much it would cost, and how much it would cost if I had to dismantle the whole desk instead and conduct a proper search. Not one chose the dismantling route, funnily enough. Gareth. If these were MLCC caps then maybe no less than .2 ohm or so , so a chance an IR non contact thermometer would pick it up with only forcing an amp through the rail, would save stressing the traces and leaving a time bomb in the works |
#14
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![]() "N_Cook" wrote in message ... Gareth Magennis wrote in message news ![]() "Arfa Daily" wrote in message ... Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) Arfa Behringer 24 channel M8000 Eurodesks used to regularly come in with one of the 100's (if not 1000's) of 17v rail bypass capacitors shorted. I used to stick 5 amps from a bench supply down the offending rail, and it would disappear in a puff of smoke within 10 seconds. Although not strictly a pro repair, I always told the customer what I was going to do, how much it would cost, and how much it would cost if I had to dismantle the whole desk instead and conduct a proper search. Not one chose the dismantling route, funnily enough. Gareth. If these were MLCC caps then maybe no less than .2 ohm or so , so a chance an IR non contact thermometer would pick it up with only forcing an amp through the rail, would save stressing the traces and leaving a time bomb in the works I suspect the remaining 999 capacitors were far more of a time bomb - this was a regular occurrence. Gareth. |
#15
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![]() "N_Cook" wrote in message ... Ian Field wrote in message ... "Arfa Daily" wrote in message ... Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. That method has located many S/C zeners for me. A non contact IR thermometer can be useful for such and similar low ohmic VTS , to wave over the errant board Maplin didn't stock those back in the days when I used brute force & ignorance to weed out dud zeners. |
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![]() "Phil Allison" wrote in message ... "Arfa Daily" Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) ** This is known as the " tune for maximum smoke " method. Often shows up short circuit bypass ceramics and regular pigtail tantalums too. How come you did not have the matching transmitter ?? I always insist on customers including them - more than once I have been given a mic and receiver pair that do not work because they are on different frequencies. .... Phil This work comes from a music shop. Usually, if it seems to be an RF issue, they will send both bits to me. In this instance, as the receive unit was obviously dead, that was all that the owner brought in. They pulled it apart in the shop, in case there was a fuse to try, but once they saw that there wasn't, they just shipped it out to me, knowing that I have a decent HP generator that's good to 2.4 GHz. I do not see any that are a channel mis-match issue, because that sort of thing is filtered in the shop. The guy that owns the shop is fairly technical and can deal with testing and replacing valves. He is able to replace HF drivers, and has been a bass unit re-coner for years. But he knows his limitations, and anything beyond that, is just passed out to me. Oddly, a couple of months ago, I had two radio mic receivers in the space of a couple of weeks, which both had the demodulator tank mis-tuned by a good half turn. Neither had been 'got-at' as far as we know, and both remained stable and correctly tuned over a soak test of several days. Neither has come bouncing back either, so it's a bit of a mystery as to why they were like it. Arfa |
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![]() "Mark Zacharias" wrote in message ... "Arfa Daily" wrote in message ... Had a JTS radio mic receiver on the bench today. "No power", said the job ticket. With 12 volts going in, the output from the four-legged LDO 8 volt regulator, was almost nothing. A quick stab around with the ohm-meter revealed about 1.7 ohms across the output. Nothing obviously short. Nothing getting hot because the regulator was in a full foldback condition. Loads of surface mount 4558's in there, as well as a good selection of more exotic ICs, and the 1.7 ohms could be measured at any of them. I had a quick word with the shop that it came from, and the guy there was of the opinion that it would not be worth pursuing even with the manufacturer, as it was well out of warranty. "He'll just have to buy a new one" he said. That made me feel bad, as I felt that I had perhaps not pursued it far enough. On the basis that the job wasn't going anywhere anyway, and time had already been spent, I decided to get brutal with it, to see if I could make the short show its face. I turned the power supply down to about 4 volts, and linked across the regulator. I then turned the supply back on and settled down to wait. As it turned out, it wasn't for very long ... A cloud of smoke and sparks shot out of a tiny little surface mount solid tantalum 1uF cap. There are hundreds of these - well, tens anyway! - all over the board. It was but a few seconds work with the iron to whip this cap off the board. The short disappeared with it, so I took my bridging link off the regulator, and let it go back to working normally with a full 12 volt input. This time, the output of the regulator was 7.96 volts, and the power LED lit. A quick tune of the signal generator up to 863 MHz, with a bit of wire in the output to act as an antenna, and the RF and AF LEDs lit. As a final check, I hooked it into an amplifier, and got audio from the generator. Sometimes it pays to persevere ... :-) Arfa I do this sometimes, but occasionally: a.) The short will burn itself open, or b.) The short is really zero point zero ohms and you start burning foil runs before any component reveals itself by getting hot. I might try the current limited method next time, but those very small voltage differences may be a problem. I don't own such a DC supply though, I'd have to use an actual resistor. Might also be a good excuse to buy a non-contact thermometer ;-) Mark Z. I actually have a non-contact IR thermometer, and it's just about OK on biggish items like chips, but nothing like tight enough on its sensing area, to be able to detect a gnat's bollock cap getting hot ! Arfa |
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On Wed, 22 Feb 2012 02:36:14 -0000, "Arfa Daily"
wrote: I actually have a non-contact IR thermometer, and it's just about OK on biggish items like chips, but nothing like tight enough on its sensing area, to be able to detect a gnat's bollock cap getting hot ! I made an attachment that resembles a black (non-reflective) soda straw, about 8 mm in diameter. It is fitted to the lens on my IR thermometer with an ugly mess of electrical tape. The idea is for only the light coming down the soda straw to hit the pyrometer. Works fine for measuring individual components (although the readings appear to be lower than expected). Got $2,000 and up? http://www.flir.com/cvs/americas/en/personalvision/view/?id=44756 I like your "big bang" method of troubleshooting. I've used when desperate, with variable success. In one case, I destroyed a transceiver when the PCB traces decided to immitate a fuse. Other times, it clearly identified a shorted capacitor, by exploding. Tantalums are rather interesting, producing a bright red glow, and belching toxic fumes. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
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Jeff Liebermann wrote in message
... On Wed, 22 Feb 2012 02:36:14 -0000, "Arfa Daily" wrote: I actually have a non-contact IR thermometer, and it's just about OK on biggish items like chips, but nothing like tight enough on its sensing area, to be able to detect a gnat's bollock cap getting hot ! I made an attachment that resembles a black (non-reflective) soda straw, about 8 mm in diameter. It is fitted to the lens on my IR thermometer with an ugly mess of electrical tape. The idea is for only the light coming down the soda straw to hit the pyrometer. Works fine for measuring individual components (although the readings appear to be lower than expected). Got $2,000 and up? http://www.flir.com/cvs/americas/en/personalvision/view/?id=44756 I like your "big bang" method of troubleshooting. I've used when desperate, with variable success. In one case, I destroyed a transceiver when the PCB traces decided to immitate a fuse. Other times, it clearly identified a shorted capacitor, by exploding. Tantalums are rather interesting, producing a bright red glow, and belching toxic fumes. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS I tried that a couple of years back and found what you found and by experiment no better resolution with or without the shroud, so went back to plain unshrouded and localising to area rather than individual SMD |
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Arfa Daily wrote:
Oddly, a couple of months ago, I had two radio mic receivers in the space of a couple of weeks, which both had the demodulator tank mis-tuned by a good half turn. Neither had been 'got-at' as far as we know, and both remained stable and correctly tuned over a soak test of several days. Neither has come bouncing back either, so it's a bit of a mystery as to why they were like it. Same make of unit? Sounds like a screw-up at the factory, and really weak QC. Somebody had the wrong tuning procedure, or the transmitter they were using to tune it was set to the wrong freq. Well, that's China for you. Jon |
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Hi, John.. I have one of the Tone Ohm units, but I'm not sure where it is at
the moment. I agree, that milliohm meters are very useful in finding circuit faults (on bare or populated boards), and some ESR meters may also be useful if the circuitry isn't massively large. I've recommended milliohm testers in SER over the years, although I'm not sure that I included any details wrt the probes. There are likely SER archived posts which may include ToneOhm milliohm meter or Polar Instruments comments. The obvious advantage to a real milliohm meter is the digital display, although they also incorporate an audio tone which changes with differences in readings/actual circuit board resistance changes. The probe for the Tone Ohm model I have (white case with red panel silkscreening), IIRC, is a fairly common 4-pin connector used for transceivers (CB, amateur radio etc) with 2 sections of small, flexible coax (one for each probe), where the 2 conductors of each probe make a 4-wire bridge-type input circuit. The 2 probes themselves aren't anything special, just ordinary probes with sharp steel tips. There is a Cal pot and built-in test point on the back panel of the ToneOhm unit I have, so there is some wiggle room for what materials might be suitable for the brobes and cables. I got some Fluke probes with sharp steel points for my Blue Bob Parker Anatek ESR meter, and they're working fine. FWIW, some instruments as you probably already know, are more critical of Zero-Set settings, and I've found that steel points break thru any surface oxides on a test piece (a coin, single solder pad or other metallic surface) and sharp steel points appear to be less problematic IME. I generally don't rely on touching probe tips together for Zero-Set, although not an issue with Bob Parker's tester, but some instruments are more fiddly.. so I like to pierce any surface contamination and use an actual reading for zero. After I bought the used Tone Ohm a number of years ago, a friend bought a similar unit by Polar Instruments (older model 900 maybe, marketed by a US company) without a probe, and I made a probe set for him from two sections of thin coax (maybe RG 174) and it worked correctly.. I vaguely recall that the probes for the Polar model utilized two sections of coax per probe using the shields as separate ground connections.. definite maybe, I guess. -- Cheers, WB .............. "John Robertson" wrote in message ... Or you could track down a Shortsqueek by Global Specialties Model SQ-1.Made in the 1970s and 80s it is a handy device to keep to track down shorts on PCBs. Using a small op-amp that changes pitch depending on how low the resistance is you can find shorts such as you describe fairly quickly as long as your ear is good for tone changes of a few Hertz. Polar Devices (UK) made Tone Ohm which was a similar device (I need a probe if anyone has a spare) that I haven't been able to test (because I'm missing the probe!). Here is the manual for Shortsqueek (470k PDF) http://www.flippers.com/pdfs/GlobalS...Model_SQ-1.pdf These turn up on eBay from time to time - I bought two for my shop and they do save hours of time (and chopping traces) every now and then... John :-#)# -- (Please post followups or tech enquiries to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
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![]() "Jon Elson" wrote in message ... Arfa Daily wrote: Oddly, a couple of months ago, I had two radio mic receivers in the space of a couple of weeks, which both had the demodulator tank mis-tuned by a good half turn. Neither had been 'got-at' as far as we know, and both remained stable and correctly tuned over a soak test of several days. Neither has come bouncing back either, so it's a bit of a mystery as to why they were like it. Same make of unit? Sounds like a screw-up at the factory, and really weak QC. Somebody had the wrong tuning procedure, or the transmitter they were using to tune it was set to the wrong freq. Well, that's China for you. Jon Nope. Two different makes, two different owners and both had been in service and previously working just fine (apparently) for a long time ... Arfa |
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![]() "Jeff Liebermann" wrote in message ... On Wed, 22 Feb 2012 02:36:14 -0000, "Arfa Daily" wrote: I actually have a non-contact IR thermometer, and it's just about OK on biggish items like chips, but nothing like tight enough on its sensing area, to be able to detect a gnat's bollock cap getting hot ! I made an attachment that resembles a black (non-reflective) soda straw, about 8 mm in diameter. It is fitted to the lens on my IR thermometer with an ugly mess of electrical tape. The idea is for only the light coming down the soda straw to hit the pyrometer. Works fine for measuring individual components (although the readings appear to be lower than expected). Got $2,000 and up? http://www.flir.com/cvs/americas/en/personalvision/view/?id=44756 I like your "big bang" method of troubleshooting. I've used when desperate, with variable success. In one case, I destroyed a transceiver when the PCB traces decided to immitate a fuse. Other times, it clearly identified a shorted capacitor, by exploding. Tantalums are rather interesting, producing a bright red glow, and belching toxic fumes. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS Yeah, it was a bit of a last resort. The print on the power rail was actually quite good quality and size, so I wasn't expecting to get a track burn up. With only 4 volts on there, I was actually expecting something to just get hot to the touch or possibly smoke gently. But yes, you are right. There was certainly a good pyrotechnic display and a lot of smoke considering how small the cap was, in very short order. I'll give your soda straw idea a try next time. Arfa |
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On Thu, 23 Feb 2012 02:44:16 -0000, "Arfa Daily"
wrote: I'll give your soda straw idea a try next time. What worked the best was a sheet of black construction paper. http://www.staples.com/Construction-Paper-9-x-12-Black/product_402652 The idea is the same as in a telescope. You don't want anything that reflects light or heat. My first attempt was a brass tube and brass washer to fit over the lens. Even painted flat black, the IR thermometer would read the temperature of the brass tube, and not the heat source. I substituted ordinary paper, which proved to be IR transparent. I also stupidly left the brass washer, which again caused local heating. Eventually, the gears operating the brain engaged, and I realized that I needed something that was opaque to IR and had minimal thermal mass. Black construction paper was the best I could find. I wanted it corrugated to minimize reflections, but that proved to be difficult to build. Several variations were built. The one that worked best was a conical like construction, that covered the entire lens on the IR thermometer end, and narrowed to almost a point on the other. However, attachment of this arrangement to the IR thermometer proved fragile, so I tried a soda straw shape, and washer cut from a shipping box. For light proofing, I buried the mess under a layer of black electrical tape. I suggest you try the cone first as it's easiest to build. I just ordered a B&D TLD100 heat leak detector, which seems to have more resolution over its narrow -30C to 150C range, than the wide temperature range common IR thermometer. $50. http://www.blackanddecker.com/power-tools/TLD100.aspx Drivel: In the past, I've ranted on building several IR flying spot scanners using bar code readers and various pyrometers. I never really finished. I demonstrated that it worked, but was very slow to respond. I'm tempted to resurrect that project and build a real far IR imager. http://groups.google.com/group/sci.electronics.equipment/browse_thread/thread/92c3879a53a8f9f1 Some ideas: http://spill.tanagram.com/2010/11/24/diy-thermal-imaging-system-for-under-200/ Moving the camera for scanning sucks. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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Jeff Liebermann wrote in message
... On Thu, 23 Feb 2012 02:44:16 -0000, "Arfa Daily" wrote: I'll give your soda straw idea a try next time. What worked the best was a sheet of black construction paper. http://www.staples.com/Construction-Paper-9-x-12-Black/product_402652 The idea is the same as in a telescope. You don't want anything that reflects light or heat. My first attempt was a brass tube and brass washer to fit over the lens. Even painted flat black, the IR thermometer would read the temperature of the brass tube, and not the heat source. I substituted ordinary paper, which proved to be IR transparent. I also stupidly left the brass washer, which again caused local heating. Eventually, the gears operating the brain engaged, and I realized that I needed something that was opaque to IR and had minimal thermal mass. Black construction paper was the best I could find. I wanted it corrugated to minimize reflections, but that proved to be difficult to build. Several variations were built. The one that worked best was a conical like construction, that covered the entire lens on the IR thermometer end, and narrowed to almost a point on the other. However, attachment of this arrangement to the IR thermometer proved fragile, so I tried a soda straw shape, and washer cut from a shipping box. For light proofing, I buried the mess under a layer of black electrical tape. I suggest you try the cone first as it's easiest to build. I just ordered a B&D TLD100 heat leak detector, which seems to have more resolution over its narrow -30C to 150C range, than the wide temperature range common IR thermometer. $50. http://www.blackanddecker.com/power-tools/TLD100.aspx Drivel: In the past, I've ranted on building several IR flying spot scanners using bar code readers and various pyrometers. I never really finished. I demonstrated that it worked, but was very slow to respond. I'm tempted to resurrect that project and build a real far IR imager. http://groups.google.com/group/sci.e...se_thread/thre ad/92c3879a53a8f9f1 Some ideas: http://spill.tanagram.com/2010/11/24...em-for-under-2 00/ Moving the camera for scanning sucks. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 I used some matt black rubber tubing .about 5mm diameter as a shroud but as I say the resolution , down to SMD dimensions , seemed to be no different with or without the tube |
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![]() N_Cook wrote: I used some matt black rubber tubing .about 5mm diameter as a shroud but as I say the resolution , down to SMD dimensions , seemed to be no different with or without the tube Mine has a short metal tube, or more like a cup, that is reflective. It seems to me that a reflective tube would work better at conducting the IR from the endpoint. -- Reply in group, but if emailing add one more zero, and remove the last word. |
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On Mon, 12 Mar 2012 15:54:56 -0400, "Tom Del Rosso"
wrote: N_Cook wrote: I used some matt black rubber tubing .about 5mm diameter as a shroud but as I say the resolution , down to SMD dimensions , seemed to be no different with or without the tube Mine has a short metal tube, or more like a cup, that is reflective. It seems to me that a reflective tube would work better at conducting the IR from the endpoint. A reflective tube is better for conducting IR to the sensor. The problem is that it also picks up plenty of IR from the sides. The point of the black construction paper tube was to measure only the IR that goes directly from the hot component to the sensor, not the junk that comes in from other components. Ideally, that could be done with a lens that focuses to a point. Lacking one of those, the tube is a tolerable 2nd best. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
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On Tue, 13 Mar 2012 15:35:50 -0700, Jeff Liebermann
wrote: On Mon, 12 Mar 2012 15:54:56 -0400, "Tom Del Rosso" wrote: N_Cook wrote: I used some matt black rubber tubing .about 5mm diameter as a shroud but as I say the resolution , down to SMD dimensions , seemed to be no different with or without the tube Mine has a short metal tube, or more like a cup, that is reflective. It seems to me that a reflective tube would work better at conducting the IR from the endpoint. A reflective tube is better for conducting IR to the sensor. The problem is that it also picks up plenty of IR from the sides. The point of the black construction paper tube was to measure only the IR that goes directly from the hot component to the sensor, not the junk that comes in from other components. Ideally, that could be done with a lens that focuses to a point. Lacking one of those, the tube is a tolerable 2nd best. Now what do they make lenses out of for that wavelength range? ?-) |
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Now, what do they make lenses out of for that
wavelength range [IR]? Germanium. |
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On Fri, 16 Mar 2012 19:26:12 -0700, josephkk
wrote: Now what do they make lenses out of for that wavelength range? Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital cameras do near IR. The ideal material for mid IR is germanium. However, that's rather expensive. http://www.edmundoptics.com/products/browse.cfm?categoryid=11&subcatid=314 Much cheaper are various plastic formulations, that pass IR. http://www.fresneltech.com/materials.html http://www.fresneltech.com/materials_graph.html http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Infrared_Transmitting For tinkering, the IR motion detectors (PIR) lenses are cheap and easy: http://www.glolab.com/pirparts/pirparts.html http://www.futurlec.com/PIR_Sensors.shtml There are also a tangle of band pass, low pass, and specialty filters. http://www.edmundoptics.com/products/browse.cfm?categoryid=41 Or, you can just be weird: http://amasci.com/amateur/irgoggl.html -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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Jeff Liebermann wrote in
: On Fri, 16 Mar 2012 19:26:12 -0700, josephkk wrote: Now what do they make lenses out of for that wavelength range? Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital cameras do near IR. The ideal material for mid IR is germanium. However, that's rather expensive. http://www.edmundoptics.com/products...d=11&subcatid= 314 Much cheaper are various plastic formulations, that pass IR. http://www.fresneltech.com/materials.html http://www.fresneltech.com/materials_graph.html http://www.eplastics.com/Plastic/Ple..._Infrared_Tran smitting For tinkering, the IR motion detectors (PIR) lenses are cheap and easy: http://www.glolab.com/pirparts/pirparts.html http://www.futurlec.com/PIR_Sensors.shtml There are also a tangle of band pass, low pass, and specialty filters. http://www.edmundoptics.com/products/browse.cfm?categoryid=41 Or, you can just be weird: http://amasci.com/amateur/irgoggl.html often,they use curved mirrors instead of lenses,for IR. and sapphire for a window. ;-) -- Jim Yanik jyanik at localnet dot com |
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![]() "Jeff Liebermann" wrote in message ... On Fri, 16 Mar 2012 19:26:12 -0700, josephkk wrote: Now what do they make lenses out of for that wavelength range? Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital cameras do near IR. The ideal material for mid IR is germanium. However, that's rather expensive. http://www.edmundoptics.com/products/browse.cfm?categoryid=11&subcatid=314 Much cheaper are various plastic formulations, that pass IR. http://www.fresneltech.com/materials.html http://www.fresneltech.com/materials_graph.html http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Infrared_Transmitting For tinkering, the IR motion detectors (PIR) lenses are cheap and easy: http://www.glolab.com/pirparts/pirparts.html http://www.futurlec.com/PIR_Sensors.shtml There are also a tangle of band pass, low pass, and specialty filters. http://www.edmundoptics.com/products/browse.cfm?categoryid=41 Or, you can just be weird: http://amasci.com/amateur/irgoggl.html -- Jeff Liebermann Hows about the lens from a an old CD laser ? Just thinking out loud ... Arfa |
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On Tue, 20 Mar 2012 18:42:03 -0000, "Arfa Daily"
wrote: Hows about the lens from a an old CD laser ? Just thinking out loud ... Arfa Maybe. The common DVD laser diode is 632nm, which is in the visible light range. Laser printers and CDROM drives are 780nm, which is near IR. Since outside light sources do not enter into a CDROM drive, there's no need for an IR bandpass filter. I couldn't find anything on the optical characteristics of the CD or DVD lens. The dark ones might be a possible bandpass filter. The clear lenses are probably not. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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![]() "Jeff Liebermann" wrote in message ... On Tue, 20 Mar 2012 18:42:03 -0000, "Arfa Daily" wrote: Hows about the lens from a an old CD laser ? Just thinking out loud ... Arfa Maybe. The common DVD laser diode is 632nm, which is in the visible light range. Laser printers and CDROM drives are 780nm, which is near IR. Since outside light sources do not enter into a CDROM drive, there's no need for an IR bandpass filter. I couldn't find anything on the optical characteristics of the CD or DVD lens. The dark ones might be a possible bandpass filter. The clear lenses are probably not. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 DVD lasers operate at visible red as you say, whilst CD lasers are near IR. CD laser lenses often appear to be optically coated, but for what reason exactly, I'm not sure. Arfa |
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On Fri, 23 Mar 2012 01:31:39 -0000, "Arfa Daily"
wrote: DVD lasers operate at visible red as you say, whilst CD lasers are near IR. CD laser lenses often appear to be optically coated, but for what reason exactly, I'm not sure. Reflective coatings are usually to minimize reflections and/or to improve signal to noise ratio by reducing the optical bandwidth. http://rick_oleson.tripod.com/index-166.html -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
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On Sat, 17 Mar 2012 06:01:37 -0700, "William Sommerwerck"
wrote: Now, what do they make lenses out of for that wavelength range [IR]? Germanium. That may work well, but it is rather spendy. Any other materials? ?-) |
#37
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On Sat, 17 Mar 2012 09:27:23 -0700, Jeff Liebermann
wrote: On Fri, 16 Mar 2012 19:26:12 -0700, josephkk wrote: Now what do they make lenses out of for that wavelength range? Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital cameras do near IR. The ideal material for mid IR is germanium. However, that's rather expensive. http://www.edmundoptics.com/products/browse.cfm?categoryid=11&subcatid=314 Much cheaper are various plastic formulations, that pass IR. http://www.fresneltech.com/materials.html http://www.fresneltech.com/materials_graph.html http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Infrared_Transmitting For tinkering, the IR motion detectors (PIR) lenses are cheap and easy: http://www.glolab.com/pirparts/pirparts.html http://www.futurlec.com/PIR_Sensors.shtml There are also a tangle of band pass, low pass, and specialty filters. http://www.edmundoptics.com/products/browse.cfm?categoryid=41 Or, you can just be weird: http://amasci.com/amateur/irgoggl.html Mid to far as i understand it. I want to look at thermal maps of electronics that may be too hot to touch thermally or electrically. The idea of forming an image with inexpensive optics and sensors appeals to me. ?-) |
#38
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On Tue, 27 Mar 2012 21:57:17 -0700, josephkk
wrote: Mid to far as i understand it. I want to look at thermal maps of electronics that may be too hot to touch thermally or electrically. I had the same idea and decided that $2,000 and up for commercial thermal imagers was too much. My idea was to convert either a supermarket scanner or laser printer rotating mirror imager, into a IR camera. Basically, it's a "flying spot scanner" and is identical to what we were using in early weather satellites to generate thermal images of the planet. I've built two failed prototypes so far, but plan to continue. The major problem is the response time of the IR detector. The guts of a PIR sensor will work, but is depressingly slow. http://www.futurlec.com/PIR_Sensors.shtml http://en.wikipedia.org/wiki/Infrared_detector Typical thermopile sensors: http://www.smartec.nl/pdf/DSSMTIR990X.PDF http://www.smartec.nl/pdf/SMTIR9902SIL.PDF I was getting about 50msec response time. At that speed, a 500 pixel line would take 25 seconds to scan. A tiny 25Kbit image would take 22 minutes. This is almost tolerable for a tripod mounted thermal camera, but not for anything hand held. There was also a major problem with thermal noise. Cryogenic cooling, using a Peltier junction device, with some manner of lens fog protection, will be needed. The idea of forming an image with inexpensive optics and sensors appeals to me. Research old technology on "mechanical television". Then, build something to work in the optical range. Once it's working as a visible light camera, switch to IR with appropriate lenses and filters. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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On Sat, 17 Mar 2012 09:27:23 -0700, Jeff Liebermann
wrote: On Fri, 16 Mar 2012 19:26:12 -0700, josephkk wrote: Now what do they make lenses out of for that wavelength range? Near, mid, or far IR? Heat is mid to far IR. Unmodified CCD digital cameras do near IR. The ideal material for mid IR is germanium. However, that's rather expensive. http://www.edmundoptics.com/products/browse.cfm?categoryid=11&subcatid=314 Much cheaper are various plastic formulations, that pass IR. http://www.fresneltech.com/materials.html http://www.fresneltech.com/materials_graph.html http://www.eplastics.com/Plastic/Plexiglass_Acrylic_Sheet_Infrared_Transmitting For tinkering, the IR motion detectors (PIR) lenses are cheap and easy: http://www.glolab.com/pirparts/pirparts.html http://www.futurlec.com/PIR_Sensors.shtml There are also a tangle of band pass, low pass, and specialty filters. http://www.edmundoptics.com/products/browse.cfm?categoryid=41 Or, you can just be weird: http://amasci.com/amateur/irgoggl.html Jeff, you are soo off the beaten path. ?-) |
#40
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On Wed, 28 Mar 2012 09:19:04 -0700, Jeff Liebermann
wrote: On Tue, 27 Mar 2012 21:57:17 -0700, josephkk wrote: Mid to far as i understand it. I want to look at thermal maps of electronics that may be too hot to touch thermally or electrically. I had the same idea and decided that $2,000 and up for commercial thermal imagers was too much. My idea was to convert either a supermarket scanner or laser printer rotating mirror imager, into a IR camera. Basically, it's a "flying spot scanner" and is identical to what we were using in early weather satellites to generate thermal images of the planet. I've built two failed prototypes so far, but plan to continue. The major problem is the response time of the IR detector. The guts of a PIR sensor will work, but is depressingly slow. http://www.futurlec.com/PIR_Sensors.shtml http://en.wikipedia.org/wiki/Infrared_detector Typical thermopile sensors: http://www.smartec.nl/pdf/DSSMTIR990X.PDF http://www.smartec.nl/pdf/SMTIR9902SIL.PDF I was getting about 50msec response time. At that speed, a 500 pixel line would take 25 seconds to scan. A tiny 25Kbit image would take 22 minutes. This is almost tolerable for a tripod mounted thermal camera, but not for anything hand held. There was also a major problem with thermal noise. Cryogenic cooling, using a Peltier junction device, with some manner of lens fog protection, will be needed. The idea of forming an image with inexpensive optics and sensors appeals to me. Research old technology on "mechanical television". Then, build something to work in the optical range. Once it's working as a visible light camera, switch to IR with appropriate lenses and filters. I have been thinking along somewhat different lines. Not close to real working ideas yet. ?-) |
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