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

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."

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.

"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

"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.

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.

"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

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

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.

"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.

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).

"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.

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

"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.

"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.

"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

"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

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

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

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

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."

"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

"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

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

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

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.

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

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?

?-)

Now, what do they make lenses out of for that
wavelength range [IR]?

Germanium.

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

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

"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

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

"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

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

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?

?-)

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.

?-)

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

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.

?-)

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.

?-)