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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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Germanium transistor sub
I think I've found the transistor that is intermittently failing in my
Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny |
#2
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Germanium transistor sub
"klem kedidelhopper" wrote in message
... I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny AF126 and NTE160, appear to have different pinouts ? http://english.electronica-pt.com/db....php?ref=AF126 and http://www.nteinc.com/specs/100to199/pdf/nte160.pdf Arfa |
#3
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Germanium transistor sub
Even if the transistor's output capacitance was far-enough "off" to
significantly detune the IF, you'd still get something. * Are you certain you installed the NTE 160 with the leads in the right positions? What happens when you put the old transistor back? You should also check the transistor with a diode-safe ohmeter. * I assume the designer would take the base-collector capacitance into account when designing the IF transformers. You'd want the latter to have significantly higher capacitance so that swapping transistors wouldn't cause a big shift in tuning. |
#4
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Germanium transistor sub
In article
, klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? From the subject, you say the original transistor is a Ge device. There's a very good chance that the "replacement" is actually a Si one. You can check this by measuring the forward conduction drop of the B-E junction -- a Ge one will be about half that of Si. If the replacement is, in fact, a Si device, you still might be able to get good performance from it by adjusting the bias point. Isaac |
#5
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Germanium transistor sub
isw wrote: From the subject, you say the original transistor is a Ge device. There's a very good chance that the "replacement" is actually a Si one. There is a 100% chance that you're wrong: http://www.nteinc.com/specs/100to199/pdf/nte160.pdf This link was also posted in the original thread: AM/FM radio troubleshooting -- It's easy to think outside the box, when you have a cutting torch. |
#6
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Germanium transistor sub
Inasmuch as the NTE device is spec'd for this sort of application, it seems
very strange you don't get something out of it. It IS possible you have the leads reversed. I'm sure anyone in this group will confirm that one can make the same mistake over and over and over and not catch it. Make sure the E and B leads aren't touching. The next step is to confirm that the replacement transistor is actually good, regardless of the ohmeter readings. Check the bias. Are the voltages correct? Or is the transistor saturated or cut off? If the bias is correct, put a 'scope and input and output, and see what's there. You might also build a simple amplifier using a GE Transistor Handbook circuit, and see whether or not it works. Barring some weird mistake on your part, I'm going to go with Sherlock and state that, as we've eliminated all the impossible stuff, the only thing logically remaining is that you have a bad transistor. |
#7
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Germanium transistor sub
On 6/4/2011 8:49 AM, William Sommerwerck wrote:
Barring some weird mistake on your part, I'm going to go with Sherlock and state that, as we've eliminated all the impossible stuff, the only thing logically remaining is that you have a bad transistor. Or the obvious, the transistor wasn't at fault to begin with. Jeff -- "Everything from Crackers to Coffins" |
#8
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Germanium transistor sub
Jeffrey Angus wrote:
On 6/4/2011 8:49 AM, William Sommerwerck wrote: Barring some weird mistake on your part, I'm going to go with Sherlock and state that, as we've eliminated all the impossible stuff, the only thing logically remaining is that you have a bad transistor. Or the obvious, the transistor wasn't at fault to begin with. Jeff Which is where I would start Jamie |
#9
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Germanium transistor sub
On Jun 4, 6:07*am, klem kedidelhopper
wrote: On Jun 4, 5:59*am, "Michael A. Terrell" wrote: isw wrote: From the subject, you say the original transistor is a Ge device. There's a very good chance that the "replacement" is actually a Si one. * *There is a 100% chance that you're wrong: http://www.nteinc.com/specs/100to199/pdf/nte160.pdf * *This link was also posted in the original thread: AM/FM radio troubleshooting -- It's easy to think outside the box, when you have a cutting torch. Yes I am aware of the reversal of emitter and base leads between the two types. I was very careful with that. I triple checked the connections each time I removed the 160 and then re installed it. I'm having a hard time picturing how one would swap B and C. Is the substitute mounted high above the board? To see if the AF160 is good or not, and to make sure the NTE is a match: could you call a community college or tech hs to see if they had a curve tracer you could use? Then you could compare to those spec sheets you downloaded. |
#10
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Germanium transistor sub
On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper
wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio. Ummm... could you take a 2nd look at the model number? Grundig makes the YB-305, but that's not germanium. http://www.universal-radio.com/catalog/portable/yb305.html Grundig also makes a 3059, but that's tubes: http://www.oldradioworld.de/3059.htm Perhaps if you disclosed the correct model number, and possibly which xsistor you're replacing, we can find a schematic, and determine if your NTE substitute is appropriate? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#11
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Germanium transistor sub
klem kedidelhopper wrote: On Jun 4, 5:59 am, "Michael A. Terrell" wrote: isw wrote: From the subject, you say the original transistor is a Ge device. There's a very good chance that the "replacement" is actually a Si one. There is a 100% chance that you're wrong: http://www.nteinc.com/specs/100to199/pdf/nte160.pdf This link was also posted in the original thread: AM/FM radio troubleshooting -- It's easy to think outside the box, when you have a cutting torch. Yes I am aware of the reversal of emitter and base leads between the two types. I was very careful with that. I triple checked the connections each time I removed the 160 and then re installed it. The radio does in fact work intermittently as it did before each time the old transistor is installed back in the radio so at this point I can still get back to square one, thankfully, (as long as the foil doesn't start lifting from the phenolic board). The ohmmeter confirms the original as well as the 160 as being a PNP Ge transistor too.There is somewhat of a difference in reverse ohmmeter readings between the 160 and the AF126 but I would have suspected that from germaniums, especially one old one and one new one anyway. Although it really shouldn't be necessary I did a search for an AF126 but the only thing that came up were some old spec sheets. I think that this one sadly is long gone. I did initially try the 160 in the circuit with the metal can lead disconnected. I didn't think that this would make any difference because when troubleshooting the chassis originally I was looking for "whiskers" as suggested to me before as possibly being the case. So I had lifted all the can shields from all the transistors and that didn't make any difference. The radio still worked intermittently. So I did finally solder the can lead on the 160 on but it still did not work, I don't want to touch the alignment because I'm just not convinced that this is where the problem is. I know that NTE's don't always work in the particular application but I wonder if perhaps this is whats going on here. I just can't help wondering if I'm missing something else though. If anyone has any further thoughts on this I would be most sincerely grateful. Lenny Once again: Check the Collector voltage. That will show if the transistor is properly biased, and if it is a good transistor. If it isn't in the ballpark of a similar radio, look for the cause. Shorted capacitors in IF cans was a common failure, but well below bad & intermittent transistors. I serviced hundreds, if not over a thousand transistor radios in the '60s & early '70s. I never saw a radio that needed alignment after replacing a transistor, unless someone had played with it. Some were poorly aligned from the factory, but those were generally the ones that sold for less than $20 new. -- It's easy to think outside the box, when you have a cutting torch. |
#12
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Germanium transistor sub
"klem kedidelhopper" wrote in message ... On Jun 4, 5:59 am, "Michael A. Terrell" wrote: isw wrote: From the subject, you say the original transistor is a Ge device. There's a very good chance that the "replacement" is actually a Si one. There is a 100% chance that you're wrong: http://www.nteinc.com/specs/100to199/pdf/nte160.pdf This link was also posted in the original thread: AM/FM radio troubleshooting -- It's easy to think outside the box, when you have a cutting torch. Yes I am aware of the reversal of emitter and base leads between the two types. I was very careful with that. I triple checked the connections each time I removed the 160 and then re installed it. The radio does in fact work intermittently as it did before each time the old transistor is installed back in the radio so at this point I can still get back to square one, thankfully, (as long as the foil doesn't start lifting from the phenolic board). The ohmmeter confirms the original as well as the 160 as being a PNP Ge transistor too.There is somewhat of a difference in reverse ohmmeter readings between the 160 and the AF126 but I would have suspected that from germaniums, especially one old one and one new one anyway. Although it really shouldn't be necessary I did a search for an AF126 but the only thing that came up were some old spec sheets. I think that this one sadly is long gone. I did initially try the 160 in the circuit with the metal can lead disconnected. I didn't think that this would make any difference because when troubleshooting the chassis originally I was looking for "whiskers" as suggested to me before as possibly being the case. So I had lifted all the can shields from all the transistors and that didn't make any difference. The radio still worked intermittently. So I did finally solder the can lead on the 160 on but it still did not work, I don't want to touch the alignment because I'm just not convinced that this is where the problem is. I know that NTE's don't always work in the particular application but I wonder if perhaps this is whats going on here. I just can't help wondering if I'm missing something else though. If anyone has any further thoughts on this I would be most sincerely grateful. Lenny OK. Let's apply a little genuine fault-finding here. When the radio goes off, does it stay off, or does it come back on as soon as you bring any test gear near it ? If it stays off, then you need to split the circuit down at the mixer. When it's working, use a 'scope to check the level of the local oscillator. Look at its frequency, and watch it move as you tune from the top to the bottom of the band. When it goes off, recheck. If the LO signal is still there, and of the same amplitude and frequency as it was before, then the problem is south of that point in the IF or detector stages. If anything has changed with the LO signal, then the problem is north of there. The LO / mixer might well be all the same stage. It was very common to use self oscillating mixers back in the days of Ge transistors. It was also common to use a winding on the ferrite rod as part of the L for the oscillator. Been a long time now, but I seem to recall them being called Reinartz (sp?) oscillators ?? As a slight aside, when a radio 'dies' like this, the AM IF stages can often be checked as being basically functional, with a screwdriver and a finger. Touching the base legs of the IF transistors will often result in some local AM station being picked up 'thinly'. Again, it's been a long time, but I seem to recall that intermittent faults like this often came down to those polyester silver foil and clear plastic cylindrical caps (they used to be made by a company called Suflex) and intermittent high value resistors. If the radio uses any of that type of cap in the LO / mixer/ RF stages, then when it goes off, just give each one that you can get at, a gentle squeeze with a pair of long-nosed pliers. Arfa |
#13
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Germanium transistor sub
Jeff Liebermann wrote: On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio. Ummm... could you take a 2nd look at the model number? Grundig makes the YB-305, but that's not germanium. http://www.universal-radio.com/catalog/portable/yb305.html Grundig also makes a 3059, but that's tubes: http://www.oldradioworld.de/3059.htm A lot of Grundig radios are almost impossible to locate schematics for. One radio with his (Transistor) TR-305 model number was for sale recently on Ebay. The newest 'TR' series listed in Sams is the TR-17, and date 1965. There are no YB models listed in Sams, BTW. It uses four AF126 transistors in the AM/FM IF Amplifier stages. Sams shows the collector voltages at 0, because each collector goes to ground through the primary of each pair of IF transformers. A modern meter will still show some voltage at the collector, but a VTVM used by Sams would barely make the needle move. The schematic shows between 4 - 6 ohms to ground from each collector. Perhaps if you disclosed the correct model number, and possibly which xsistor you're replacing, we can find a schematic, and determine if your NTE substitute is appropriate? He said it was AF126, which does cross to ECG/NTE 160. -- It's easy to think outside the box, when you have a cutting torch. |
#14
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Germanium transistor sub
On Jun 4, 12:57*pm, "Michael A. Terrell"
wrote: Jeff Liebermann wrote: On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio. Ummm... could you take a 2nd look at the model number? *Grundig makes the YB-305, but that's not germanium. http://www.universal-radio.com/catalog/portable/yb305.html Grundig also makes a 3059, but that's tubes: http://www.oldradioworld.de/3059.htm * *A lot of Grundig radios are almost impossible to locate schematics for. *One radio with his (Transistor) TR-305 model number was for sale recently on Ebay. * *The newest 'TR' series listed in Sams is the TR-17, and date 1965. There are no YB models listed in Sams, BTW. * It uses four AF126 transistors in the AM/FM IF Amplifier stages. *Sams shows the collector voltages at 0, because each collector goes to ground through the primary of each pair of IF transformers. *A modern meter will still show some voltage at the collector, but a VTVM used by Sams would barely make the needle move. *The schematic shows between 4 - 6 ohms to ground from each collector. Perhaps if you disclosed the correct model number, and possibly which xsistor you're replacing, we can find a schematic, and determine if your NTE substitute is appropriate? * *He said it was AF126, which does cross to ECG/NTE 160. -- It's easy to think outside the box, when you have a cutting torch. A lot of good information guys. I'm sorry I didn't include it in this new post but the radio model is "Transistor 305".It was given to me around 1970 and it wasn't new then so I'm guessing a bit here. It is late 60's vintage I think. And I do have a schematic and foil side board layout too.I did buy two of these 160's. (I wasn't going to open the second if I didn't have to as they were 5.50 apiece) but maybe this one is bad. I didn't think I'd have to touch the alignment either Michael. Just figured that it would work even somewhat.Lenny. |
#15
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Germanium transistor sub
klem kedidelhopper wrote: On Jun 4, 12:57 pm, "Michael A. Terrell" wrote: Jeff Liebermann wrote: On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio. Ummm... could you take a 2nd look at the model number? Grundig makes the YB-305, but that's not germanium. http://www.universal-radio.com/catalog/portable/yb305.html Grundig also makes a 3059, but that's tubes: http://www.oldradioworld.de/3059.htm A lot of Grundig radios are almost impossible to locate schematics for. One radio with his (Transistor) TR-305 model number was for sale recently on Ebay. The newest 'TR' series listed in Sams is the TR-17, and date 1965. There are no YB models listed in Sams, BTW. It uses four AF126 transistors in the AM/FM IF Amplifier stages. Sams shows the collector voltages at 0, because each collector goes to ground through the primary of each pair of IF transformers. A modern meter will still show some voltage at the collector, but a VTVM used by Sams would barely make the needle move. The schematic shows between 4 - 6 ohms to ground from each collector. Perhaps if you disclosed the correct model number, and possibly which xsistor you're replacing, we can find a schematic, and determine if your NTE substitute is appropriate? He said it was AF126, which does cross to ECG/NTE 160. A lot of good information guys. I'm sorry I didn't include it in this new post but the radio model is "Transistor 305".It was given to me around 1970 and it wasn't new then so I'm guessing a bit here. It is late 60's vintage I think. And I do have a schematic and foil side board layout too.I did buy two of these 160's. (I wasn't going to open the second if I didn't have to as they were 5.50 apiece) but maybe this one is bad. I didn't think I'd have to touch the alignment either Michael. Just figured that it would work even somewhat.Lenny. When it isn't working, check the signal at the collector of each IF amp with your scope. Any shop scope will display an AM IF. If it disappears at some stage, find out why. If it is missing at the mixer output, check continuity on the first IF transformer. -- It's easy to think outside the box, when you have a cutting torch. |
#16
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Germanium transistor sub
A lot of good information guys. I'm sorry I didn't include it in this
new post but the radio model is "Transistor 305".It was given to me around 1970 and it wasn't new then so I'm guessing a bit here. It is late 60's vintage I think. And I do have a schematic and foil side board layout too.I did buy two of these 160's. (I wasn't going to open the second if I didn't have to as they were 5.50 apiece) but maybe this one is bad. I didn't think I'd have to touch the alignment either Michael. Just figured that it would work even somewhat. As I said, you should have been getting something, even if the IF alignment wasn't spot-on. $5.50? Ouch! Be careful handling the device. Transistors can be damaged by static electricity. When opening the box, after -- uh -- discharging myself, I'd dump the transistor onto a piece of aluminum foil, then roll up the transistor in the foil until I was ready to insert it. |
#17
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Germanium transistor sub
"Michael A. Terrell" wrote in message ... klem kedidelhopper wrote: On Jun 4, 5:59 am, "Michael A. Terrell" wrote: isw wrote: From the subject, you say the original transistor is a Ge device. There's a very good chance that the "replacement" is actually a Si one. There is a 100% chance that you're wrong: http://www.nteinc.com/specs/100to199/pdf/nte160.pdf This link was also posted in the original thread: AM/FM radio troubleshooting -- It's easy to think outside the box, when you have a cutting torch. Yes I am aware of the reversal of emitter and base leads between the two types. I was very careful with that. I triple checked the connections each time I removed the 160 and then re installed it. The radio does in fact work intermittently as it did before each time the old transistor is installed back in the radio so at this point I can still get back to square one, thankfully, (as long as the foil doesn't start lifting from the phenolic board). The ohmmeter confirms the original as well as the 160 as being a PNP Ge transistor too.There is somewhat of a difference in reverse ohmmeter readings between the 160 and the AF126 but I would have suspected that from germaniums, especially one old one and one new one anyway. Although it really shouldn't be necessary I did a search for an AF126 but the only thing that came up were some old spec sheets. I think that this one sadly is long gone. I did initially try the 160 in the circuit with the metal can lead disconnected. I didn't think that this would make any difference because when troubleshooting the chassis originally I was looking for "whiskers" as suggested to me before as possibly being the case. So I had lifted all the can shields from all the transistors and that didn't make any difference. The radio still worked intermittently. So I did finally solder the can lead on the 160 on but it still did not work, I don't want to touch the alignment because I'm just not convinced that this is where the problem is. I know that NTE's don't always work in the particular application but I wonder if perhaps this is whats going on here. I just can't help wondering if I'm missing something else though. If anyone has any further thoughts on this I would be most sincerely grateful. Lenny Once again: Check the Collector voltage. That will show if the transistor is properly biased, and if it is a good transistor. If it isn't in the ballpark of a similar radio, look for the cause. Shorted capacitors in IF cans was a common failure, but well below bad & intermittent transistors. I serviced hundreds, if not over a thousand transistor radios in the '60s & early '70s. I never saw a radio that needed alignment after replacing a transistor, I've even got away with replacing transistors in UHF tuners most times I attempted it. |
#18
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Germanium transistor sub
"Michael A. Terrell" wrote in message ... Jeff Liebermann wrote: On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio. Ummm... could you take a 2nd look at the model number? Grundig makes the YB-305, but that's not germanium. http://www.universal-radio.com/catalog/portable/yb305.html Grundig also makes a 3059, but that's tubes: http://www.oldradioworld.de/3059.htm A lot of Grundig radios are almost impossible to locate schematics for. One radio with his (Transistor) TR-305 model number was for sale recently on Ebay. In contrast, most of their TVs had a service sheet stowed in a slot inside the cabinet. |
#19
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Germanium transistor sub
Ian Field wrote: "Michael A. Terrell" wrote in message ... klem kedidelhopper wrote: On Jun 4, 5:59 am, "Michael A. Terrell" wrote: isw wrote: From the subject, you say the original transistor is a Ge device. There's a very good chance that the "replacement" is actually a Si one. There is a 100% chance that you're wrong: http://www.nteinc.com/specs/100to199/pdf/nte160.pdf This link was also posted in the original thread: AM/FM radio troubleshooting -- It's easy to think outside the box, when you have a cutting torch. Yes I am aware of the reversal of emitter and base leads between the two types. I was very careful with that. I triple checked the connections each time I removed the 160 and then re installed it. The radio does in fact work intermittently as it did before each time the old transistor is installed back in the radio so at this point I can still get back to square one, thankfully, (as long as the foil doesn't start lifting from the phenolic board). The ohmmeter confirms the original as well as the 160 as being a PNP Ge transistor too.There is somewhat of a difference in reverse ohmmeter readings between the 160 and the AF126 but I would have suspected that from germaniums, especially one old one and one new one anyway. Although it really shouldn't be necessary I did a search for an AF126 but the only thing that came up were some old spec sheets. I think that this one sadly is long gone. I did initially try the 160 in the circuit with the metal can lead disconnected. I didn't think that this would make any difference because when troubleshooting the chassis originally I was looking for "whiskers" as suggested to me before as possibly being the case. So I had lifted all the can shields from all the transistors and that didn't make any difference. The radio still worked intermittently. So I did finally solder the can lead on the 160 on but it still did not work, I don't want to touch the alignment because I'm just not convinced that this is where the problem is. I know that NTE's don't always work in the particular application but I wonder if perhaps this is whats going on here. I just can't help wondering if I'm missing something else though. If anyone has any further thoughts on this I would be most sincerely grateful. Lenny Once again: Check the Collector voltage. That will show if the transistor is properly biased, and if it is a good transistor. If it isn't in the ballpark of a similar radio, look for the cause. Shorted capacitors in IF cans was a common failure, but well below bad & intermittent transistors. I serviced hundreds, if not over a thousand transistor radios in the '60s & early '70s. I never saw a radio that needed alignment after replacing a transistor, I've even got away with replacing transistors in UHF tuners most times I attempted it. I did it all the time in CATV converters where the L.O. was at 1.1 GHz. You had to bend the leads exactly like the original. -- It's easy to think outside the box, when you have a cutting torch. |
#20
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Germanium transistor sub
Ian Field wrote: "Michael A. Terrell" ? wrote in message ... ? ? Jeff Liebermann wrote: ?? ?? On Fri, 3 Jun 2011 17:39:30 -0700 (PDT), klem kedidelhopper ?? ? wrote: ?? ?? ?I think I've found the transistor that is intermittently failing in my ?? ?Grundig 305 transistor radio. ?? ?? Ummm... could you take a 2nd look at the model number? Grundig makes ?? the YB-305, but that's not germanium. ?? ?http://www.universal-radio.com/catal...le/yb305.html? ?? Grundig also makes a 3059, but that's tubes: ?? ?http://www.oldradioworld.de/3059.htm? ? ? A lot of Grundig radios are almost impossible to locate schematics ? for. One radio with his (Transistor) TR-305 model number was for sale ? recently on Ebay. In contrast, most of their TVs had a service sheet stowed in a slot inside the cabinet. Until someone removed it. How many of those old TV schematics are available on line, and for free? General Electric, Sears-Silvertone and other companies did the same thing in the US, but they were usually missing whenever I cracked the case on one. -- It's easy to think outside the box, when you have a cutting torch. |
#21
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Germanium transistor sub
On Jun 4, 2:39*am, klem kedidelhopper
wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio *does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny Hi... I can send You a AF126. You pay the postage, the transistor You can have for free. Bo-Lennart Karlsson Falun, SWEDEN |
#22
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Germanium transistor sub
On Jun 5, 5:15*am, Bo-Lennart wrote:
On Jun 4, 2:39*am, klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio *does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny Hi... I can send You a AF126. You pay the postage, the transistor You can have for free. Bo-Lennart Karlsson Falun, SWEDEN Hi, What do you think the postage to the US will be? Thanks, Lenny |
#23
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Germanium transistor sub
"isw" wrote in message ]... In article , klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? From the subject, you say the original transistor is a Ge device. There's a very good chance that the "replacement" is actually a Si one. You can check this by measuring the forward conduction drop of the B-E junction -- a Ge one will be about half that of Si. If the replacement is, in fact, a Si device, you still might be able to get good performance from it by adjusting the bias point. There seems to be a consensus of opinion that the OP has indeed selected a suitable Ge replacement, however I suspect that even if a Si part had been fitted the consequenses wouldn't be as serious as it not working at all. Any sort of decent quality radio would have automatic bias common emitter stages, the base bias is set by a voltage divider - that and the value of the emitter resistor determine the collector current. The self compensating nature of the circuit would tend to ensure a relatively small reduction in collector current, the main problem I can think of is that AGC is often fed at the bottom of the base bias divider, so using a transistor with a higher Vbe may have a similar effect to a large AGC control voltage - very low gain maybe, but totally inoperative; doubtful. |
#24
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Germanium transistor sub
"Ian Field" wrote in message
... Any sort of decent quality radio would have automatic bias common emitter stages, the base bias is set by a voltage divider - that and the value of the emitter resistor determine the collector current. The self compensating nature of the circuit would tend to ensure a relatively small reduction in collector current, the main problem I can think of is that AGC is often fed at the bottom of the base bias divider, so using a transistor with a higher Vbe may have a similar effect to a large AGC control voltage - very low gain maybe, but totally inoperative; doubtful. This isn't quite the way I learned it in school. The kind of bias you're describing tends to keep collector current constant with beta variations. Vbe is taken into account in the design. I don't think a circuit intended for 0.2 to 0.3 volts would work with a transistor needing 0.6 to 0.7 volts. |
#25
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Germanium transistor sub
"William Sommerwerck" wrote in message ... "Ian Field" wrote in message ... Any sort of decent quality radio would have automatic bias common emitter stages, the base bias is set by a voltage divider - that and the value of the emitter resistor determine the collector current. The self compensating nature of the circuit would tend to ensure a relatively small reduction in collector current, the main problem I can think of is that AGC is often fed at the bottom of the base bias divider, so using a transistor with a higher Vbe may have a similar effect to a large AGC control voltage - very low gain maybe, but totally inoperative; doubtful. This isn't quite the way I learned it in school. The kind of bias you're describing tends to keep collector current constant with beta variations. Vbe is taken into account in the design. I don't think a circuit intended for 0.2 to 0.3 volts would work with a transistor needing 0.6 to 0.7 volts. Collector current does fall, but there is also a corresponding fall in emitter current wich reduces the emitter resistor volt drop - which goes some way to compensating the higher Vbe. So it doesn't result in the transistor being completely cut off - as would happen if the emitter went straight to ground without an emitter resistor. |
#26
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Germanium transistor sub
Ian Field wrote: "isw" wrote in message ]... In article , klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? From the subject, you say the original transistor is a Ge device. There's a very good chance that the "replacement" is actually a Si one. You can check this by measuring the forward conduction drop of the B-E junction -- a Ge one will be about half that of Si. If the replacement is, in fact, a Si device, you still might be able to get good performance from it by adjusting the bias point. There seems to be a consensus of opinion that the OP has indeed selected a suitable Ge replacement, however I suspect that even if a Si part had been fitted the consequenses wouldn't be as serious as it not working at all. Any sort of decent quality radio would have automatic bias common emitter stages, the base bias is set by a voltage divider - that and the value of the emitter resistor determine the collector current. The 'Emmiter resistor in similar radios is nothing more than the DC rsesistance of the AM & FM IF transformer primaries in series. The self compensating nature of the circuit would tend to ensure a relatively small reduction in collector current, the main problem I can think of is that AGC is often fed at the bottom of the base bias divider, so using a transistor with a higher Vbe may have a similar effect to a large AGC control voltage - very low gain maybe, but totally inoperative; doubtful. -- It's easy to think outside the box, when you have a cutting torch. |
#27
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Germanium transistor sub
If the radio is intermitent it does not mean that necessarily the
transistor, i think of one probable cause is the variable capacitor besides if the transistor you mentioned is part of the if section then you may check with another radio tuning a frequency so produces an harmonics in the good radio so you know the mixer stage is working then you can inyect a signal with your finger in the base of the first if transistor and a radio station should be heard. Have you tried to resolder all points and verify all paths are in god condition. Hope it can help. rgds On Jun 4, 2:39*am, klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio *does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny Hi... I can send You a AF126. You pay the postage, the transistor You can have for free. Bo-Lennart Karlsson Falun, SWEDEN Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text - - Show quoted text - |
#28
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Germanium transistor sub
klem kedidelhopper wrote in message
... On Jun 6, 9:37 pm, mloo55 wrote: If the radio is intermitent it does not mean that necessarily the transistor, i think of one probable cause is the variable capacitor besides if the transistor you mentioned is part of the if section then you may check with another radio tuning a frequency so produces an harmonics in the good radio so you know the mixer stage is working then you can inyect a signal with your finger in the base of the first if transistor and a radio station should be heard. Have you tried to resolder all points and verify all paths are in god condition. Hope it can help. rgds On Jun 4, 2:39 am, klem kedidelhopper wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny Hi... I can send You a AF126. You pay the postage, the transistor You can have for free. Bo-Lennart Karlsson Falun, SWEDEN Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text - - Show quoted text - Well the odd thing is that the radio always starts out working perfectly. It will run consistently for anywhere from ten minutes to sometimes two hours. It seemed that at first operating it at low volume settings may have precipitated the problem but now I'm not so sure about that. However once the intermittent condition begins it continues until the unit is shut off for a period of time. After that the period of time it takes for the intermittent condition to start again after a subsequent power on is directly proportional to the time the radio has been off. I managed to measure all transistor voltages during an "OK" period. I then took similar voltage readings during failure. As expected all voltages on all transistors were affected, however the voltages measured at the terminals of this particular transistor in question are all the same, (about 3.0volts) when the failure condition occurs. It was for this reason i suspected this transistor, (as improbable as this may seem), of developing what looks like a "dynamic" b e c short. Lenny ++++ In that case look for C problems |
#29
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Germanium transistor sub
On Jun 7, 4:40*pm, Archon wrote:
On 6/7/2011 5:47 PM, klem kedidelhopper wrote: On Jun 6, 9:37 pm, *wrote: If the radio is intermitent it does not mean that necessarily the transistor, i think of one probable cause is the variable capacitor besides if the transistor you *mentioned is part of the if section then you may check with another radio tuning a frequency so produces an harmonics in the good radio so you know the mixer stage is working then you can inyect a signal with your finger in the base of the first if transistor and a radio station should be heard. Have you tried to resolder all points and verify all paths are in god condition. Hope it can help. rgds On Jun 4, 2:39 am, klem wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio *does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny Hi... I can send You a AF126. You pay the postage, the transistor You can have for free. Bo-Lennart Karlsson Falun, SWEDEN Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text - - Show quoted text - Well the odd thing is that the radio always starts out working perfectly. It will run consistently for anywhere from ten minutes to sometimes two hours. It seemed that at first operating it at low volume settings may have precipitated the problem but now I'm not so sure about that. However once the intermittent condition begins it continues until the unit is shut off for a period of time. After that the period of time it takes for the intermittent condition to start again after a subsequent power on is directly proportional to the time the radio has been off. I managed to measure all transistor voltages during an "OK" period. I then took similar voltage readings during failure. As expected all voltages on all transistors were affected, however the voltages measured at the terminals of this particular transistor in question are all the same, (about 3.0volts) when the failure condition occurs. It was for this reason i suspected this transistor, (as improbable as this may seem), of developing what looks like a "dynamic" b e c short. Lenny Cracked volume control pot In that case he could temporarily replace the pot with two resistors, right? And see if the circuit goes intermittent. |
#30
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Germanium transistor sub
On Jun 8, 10:51*am, spamtrap1888 wrote:
On Jun 7, 4:40*pm, Archon wrote: On 6/7/2011 5:47 PM, klem kedidelhopper wrote: On Jun 6, 9:37 pm, *wrote: If the radio is intermitent it does not mean that necessarily the transistor, i think of one probable cause is the variable capacitor besides if the transistor you *mentioned is part of the if section then you may check with another radio tuning a frequency so produces an harmonics in the good radio so you know the mixer stage is working then you can inyect a signal with your finger in the base of the first if transistor and a radio station should be heard. Have you tried to resolder all points and verify all paths are in god condition. Hope it can help. rgds On Jun 4, 2:39 am, klem wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio *does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny Hi... I can send You a AF126. You pay the postage, the transistor You can have for free. Bo-Lennart Karlsson Falun, SWEDEN Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text - - Show quoted text - Well the odd thing is that the radio always starts out working perfectly. It will run consistently for anywhere from ten minutes to sometimes two hours. It seemed that at first operating it at low volume settings may have precipitated the problem but now I'm not so sure about that. However once the intermittent condition begins it continues until the unit is shut off for a period of time. After that the period of time it takes for the intermittent condition to start again after a subsequent power on is directly proportional to the time the radio has been off. I managed to measure all transistor voltages during an "OK" period. I then took similar voltage readings during failure. As expected all voltages on all transistors were affected, however the voltages measured at the terminals of this particular transistor in question are all the same, (about 3.0volts) when the failure condition occurs. It was for this reason i suspected this transistor, (as improbable as this may seem), of developing what looks like a "dynamic" b e c short. Lenny Cracked volume control pot In that case he could temporarily replace the pot with two resistors, right? And see if the circuit goes intermittent. Because it always starts out working, and this is definitely consistent. I really feel that this is an active component problem. Lenny |
#31
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Germanium transistor sub
In that case he could temporarily replace the pot with two
resistors, right? And see if the circuit goes intermittent. Because it always starts out working, and this is definitely consistent. I really feel that this is an active component problem. Maybe, maybe not. (I'm inclined to agree "yes, it is", when you say that the transistor has the same voltage on all terminals.) But you really need to put a 'scope on the unit, and step through it. |
#32
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Germanium transistor sub
"klem kedidelhopper" wrote in message ... On Jun 8, 10:51 am, spamtrap1888 wrote: On Jun 7, 4:40 pm, Archon wrote: On 6/7/2011 5:47 PM, klem kedidelhopper wrote: On Jun 6, 9:37 pm, wrote: If the radio is intermitent it does not mean that necessarily the transistor, i think of one probable cause is the variable capacitor besides if the transistor you mentioned is part of the if section then you may check with another radio tuning a frequency so produces an harmonics in the good radio so you know the mixer stage is working then you can inyect a signal with your finger in the base of the first if transistor and a radio station should be heard. Have you tried to resolder all points and verify all paths are in god condition. Hope it can help. rgds On Jun 4, 2:39 am, klem wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny Hi... I can send You a AF126. You pay the postage, the transistor You can have for free. Bo-Lennart Karlsson Falun, SWEDEN Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text - - Show quoted text - Well the odd thing is that the radio always starts out working perfectly. It will run consistently for anywhere from ten minutes to sometimes two hours. It seemed that at first operating it at low volume settings may have precipitated the problem but now I'm not so sure about that. However once the intermittent condition begins it continues until the unit is shut off for a period of time. After that the period of time it takes for the intermittent condition to start again after a subsequent power on is directly proportional to the time the radio has been off. I managed to measure all transistor voltages during an "OK" period. I then took similar voltage readings during failure. As expected all voltages on all transistors were affected, however the voltages measured at the terminals of this particular transistor in question are all the same, (about 3.0volts) when the failure condition occurs. It was for this reason i suspected this transistor, (as improbable as this may seem), of developing what looks like a "dynamic" b e c short. Lenny Cracked volume control pot In that case he could temporarily replace the pot with two resistors, right? And see if the circuit goes intermittent. Because it always starts out working, and this is definitely consistent. I really feel that this is an active component problem. Lenny If you have the schematics for the radio, then it should be no problem figuring out what is going wrong. There really can't be very much that could cause all three terminals of the transistor to assume the same voltage. Something amiss with the emitter return maybe ? If the base is biased with respect to ground, and the emitter is returned to ground, then you must measure a difference between the base and emitter, equivalent to a germanium P-N junction drop. If the emitter return goes open, then you might well read (almost) the same voltage at the emitter and base, and possibly the collector too. Arfa |
#33
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Germanium transistor sub
Arfa Daily wrote: "klem kedidelhopper" wrote in message ... On Jun 8, 10:51 am, spamtrap1888 wrote: On Jun 7, 4:40 pm, Archon wrote: On 6/7/2011 5:47 PM, klem kedidelhopper wrote: On Jun 6, 9:37 pm, wrote: If the radio is intermitent it does not mean that necessarily the transistor, i think of one probable cause is the variable capacitor besides if the transistor you mentioned is part of the if section then you may check with another radio tuning a frequency so produces an harmonics in the good radio so you know the mixer stage is working then you can inyect a signal with your finger in the base of the first if transistor and a radio station should be heard. Have you tried to resolder all points and verify all paths are in god condition. Hope it can help. rgds On Jun 4, 2:39 am, klem wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny Hi... I can send You a AF126. You pay the postage, the transistor You can have for free. Bo-Lennart Karlsson Falun, SWEDEN Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text - - Show quoted text - Well the odd thing is that the radio always starts out working perfectly. It will run consistently for anywhere from ten minutes to sometimes two hours. It seemed that at first operating it at low volume settings may have precipitated the problem but now I'm not so sure about that. However once the intermittent condition begins it continues until the unit is shut off for a period of time. After that the period of time it takes for the intermittent condition to start again after a subsequent power on is directly proportional to the time the radio has been off. I managed to measure all transistor voltages during an "OK" period. I then took similar voltage readings during failure. As expected all voltages on all transistors were affected, however the voltages measured at the terminals of this particular transistor in question are all the same, (about 3.0volts) when the failure condition occurs. It was for this reason i suspected this transistor, (as improbable as this may seem), of developing what looks like a "dynamic" b e c short. Lenny Cracked volume control pot In that case he could temporarily replace the pot with two resistors, right? And see if the circuit goes intermittent. Because it always starts out working, and this is definitely consistent. I really feel that this is an active component problem. Lenny If you have the schematics for the radio, then it should be no problem figuring out what is going wrong. There really can't be very much that could cause all three terminals of the transistor to assume the same voltage. Something amiss with the emitter return maybe ? If the base is biased with respect to ground, and the emitter is returned to ground, then you must measure a difference between the base and emitter, equivalent to a germanium P-N junction drop. If the emitter return goes open, then you might well read (almost) the same voltage at the emitter and base, and possibly the collector too. It's a PNP transistor. The emitter has the highest voltage, so it is something opening in the collector path to ground. When it opens, the base voltage rises because the transistor is no longer biased properly. Arfa -- It's easy to think outside the box, when you have a cutting torch. |
#34
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Germanium transistor sub
"Michael A. Terrell" wrote in message m... Arfa Daily wrote: "klem kedidelhopper" wrote in message ... On Jun 8, 10:51 am, spamtrap1888 wrote: On Jun 7, 4:40 pm, Archon wrote: On 6/7/2011 5:47 PM, klem kedidelhopper wrote: On Jun 6, 9:37 pm, wrote: If the radio is intermitent it does not mean that necessarily the transistor, i think of one probable cause is the variable capacitor besides if the transistor you mentioned is part of the if section then you may check with another radio tuning a frequency so produces an harmonics in the good radio so you know the mixer stage is working then you can inyect a signal with your finger in the base of the first if transistor and a radio station should be heard. Have you tried to resolder all points and verify all paths are in god condition. Hope it can help. rgds On Jun 4, 2:39 am, klem wrote: I think I've found the transistor that is intermittently failing in my Grundig 305 transistor radio.It is an AF126. I obtained an NTE 160 which is supposed to replace the AF126. however I installed it and the radio does not work at all. I wouldn't think that I would have to do a complete IF alignment after simply replacing a transistor, that is I would think that even if the new part detuned the circuit slightly, I would expect to get something through. Any opinions on this? Thanks, Lenny Hi... I can send You a AF126. You pay the postage, the transistor You can have for free. Bo-Lennart Karlsson Falun, SWEDEN Hi, What do you think the postage to the US will be? Thanks, Lenny- Hide quoted text - - Show quoted text - Well the odd thing is that the radio always starts out working perfectly. It will run consistently for anywhere from ten minutes to sometimes two hours. It seemed that at first operating it at low volume settings may have precipitated the problem but now I'm not so sure about that. However once the intermittent condition begins it continues until the unit is shut off for a period of time. After that the period of time it takes for the intermittent condition to start again after a subsequent power on is directly proportional to the time the radio has been off. I managed to measure all transistor voltages during an "OK" period. I then took similar voltage readings during failure. As expected all voltages on all transistors were affected, however the voltages measured at the terminals of this particular transistor in question are all the same, (about 3.0volts) when the failure condition occurs. It was for this reason i suspected this transistor, (as improbable as this may seem), of developing what looks like a "dynamic" b e c short. Lenny Cracked volume control pot In that case he could temporarily replace the pot with two resistors, right? And see if the circuit goes intermittent. Because it always starts out working, and this is definitely consistent. I really feel that this is an active component problem. Lenny If you have the schematics for the radio, then it should be no problem figuring out what is going wrong. There really can't be very much that could cause all three terminals of the transistor to assume the same voltage. Something amiss with the emitter return maybe ? If the base is biased with respect to ground, and the emitter is returned to ground, then you must measure a difference between the base and emitter, equivalent to a germanium P-N junction drop. If the emitter return goes open, then you might well read (almost) the same voltage at the emitter and base, and possibly the collector too. It's a PNP transistor. The emitter has the highest voltage, so it is something opening in the collector path to ground. When it opens, the base voltage rises because the transistor is no longer biased properly. I haven't got a copy of the circuit to hand, but I'm not sure that I understand what you're saying. A PNP circuit is just the same as an NPN circuit, but with the battery upside down. Ground is ground and bias is bias, applied between the base and emitter. Doesn't matter whether it's a PNP or an NPN transistor, the ground reference is just the opposite pole of the battery. The emitter having the "highest voltage" is basically an arbitrary term as that voltage could be 'higher' in a positive or negative direction, depending on where you are taking to be your measurement reference. Things get a little more complicated to get your head around, where the circuit is powered the 'conventional' way up, but the transistors are in upside down. Maybe that's what you're saying here ? Arfa |
#35
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Germanium transistor sub
It's a PNP transistor. The emitter has the highest voltage, so it is
something opening in the collector path to ground. When it opens, the base voltage rises because the transistor is no longer biased properly. I haven't got a copy of the circuit to hand, but I'm not sure that I understand what you're saying. A PNP circuit is just the same as an NPN circuit, but with the battery upside down. Ground is ground and bias is bias, applied between the base and emitter. Doesn't matter whether it's a PNP or an NPN transistor, the ground reference is just the opposite pole of the battery. The emitter having the "highest voltage" is basically an arbitrary term as that voltage could be 'higher' in a positive or negative direction, depending on where you are taking to be your measurement reference. Things get a little more complicated to get your head around, where the circuit is powered the 'conventional' way up, but the transistors are in upside down. Maybe that's what you're saying here ? I was going to demur, too. In a junction transistor, the EB junction is forward-biased, the BC junction reverse-biased. The EB junction can be correctly biased even if the collector is dangling. I don't see how opening the collector's path to its intended voltage source would alter the base voltage. |
#36
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Germanium transistor sub
"William Sommerwerck" wrote in message ... It's a PNP transistor. The emitter has the highest voltage, so it is something opening in the collector path to ground. When it opens, the base voltage rises because the transistor is no longer biased properly. I haven't got a copy of the circuit to hand, but I'm not sure that I understand what you're saying. A PNP circuit is just the same as an NPN circuit, but with the battery upside down. Ground is ground and bias is bias, applied between the base and emitter. Doesn't matter whether it's a PNP or an NPN transistor, the ground reference is just the opposite pole of the battery. The emitter having the "highest voltage" is basically an arbitrary term as that voltage could be 'higher' in a positive or negative direction, depending on where you are taking to be your measurement reference. Things get a little more complicated to get your head around, where the circuit is powered the 'conventional' way up, but the transistors are in upside down. Maybe that's what you're saying here ? I was going to demur, too. In a junction transistor, the EB junction is forward-biased, the BC junction reverse-biased. The EB junction can be correctly biased even if the collector is dangling. I don't see how opening the collector's path to its intended voltage source would alter the base voltage. Agreed Arfa |
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