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 Post subject: Re: Transistor types
PostPosted: Jan Sun 08, 2017 9:32 pm 
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Glad to hear you found it....but please note:
You also had your meter reversed. With the battery reversed, you should have been measuring positive voltages with respect to ground.

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 Post subject: Re: Transistor types
PostPosted: Jan Sun 08, 2017 10:39 pm 
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That's right mark but only because it was wired wrong.

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 Post subject: Re: Transistor types
PostPosted: Jan Sun 08, 2017 10:52 pm 
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devildog63 wrote:
That's right mark but only because it was wired wrong.



No, you had to reverse the leads on the voltmeter, too, to get negative readings. The negative/black lead of the voltmeter should go to ground, the positive/red lead should go to the probe. If you had the battery attached with the negative going to ground, only positive voltages would be present at any point.

Brett


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 Post subject: Re: Transistor types
PostPosted: Jan Sun 08, 2017 10:59 pm 
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No. I had positive lead going to positive terminal on the switch and since positive is ground on this schematic , I believe it correct, I used the black lead from the meter negative to probe the test points. Is that incorrect?

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 Post subject: Re: Transistor types
PostPosted: Jan Sun 08, 2017 11:10 pm 
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devildog63 wrote:
No. I had positive lead going to positive terminal on the switch and since positive is ground on this schematic , I believe it correct, I used the black lead from the meter negative to probe the test points. Is that incorrect?


Yes, and that's what sent us off into the weeds. The original voltages were taken with the black/negative lead attached to ground (which is the switch in this case {note that there is no difference between the two terminals when it is "on"}) and the positive to the probe. Change it around to that, then take the readings with the battery connected correctly, I think you will find that all the voltages are negative and close to as intended. If it had been the correct way around, it would have been immediately obvious that the battery was backwards (as was suspected earlier).

It's still possible you have the collector and emitter misidentified but that will show with the corrected voltage readings (and the fact that it now works).

Note that since you ran it with the polarity reversed for an extended period, you stressed most of the electrolytic capacitors with reverse voltage. I am slightly surprised you didn't have any of them blow, maybe 9v the wrong was it's quite enough. I would, nonetheless, replace at least C1 and C2 again to just to avoid a premature failure due to latent damage that might have created.

Brett


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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 12:20 am 
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Bottom line:
You could not have gotten these measurements without some combination of errors. If we assume that C, B, and E were correctly identified, then there is no way to get those readings without reversing the battery AND reversing the meter connections.
I'll try to post something on how the transistors circuits would behave in this scenario.

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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 1:09 am 
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I'm trying to follow this, on the schematic positive is circuit ground , the test point I used was where the positive battery lead connected, even though it was actually negative cause the battery was reversed. All my measurements were negative but not what the drawing called for. The only way I can see me having them reversed is because I thought the battery was connected properly. Anyway I don't understand how I had the leads reversed. I asked early on in the thread where I needed to connect the leads and I thought I had them right.

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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 1:33 am 
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devildog63 wrote:
I'm trying to follow this, on the schematic positive is circuit ground , the test point I used was where the positive battery lead connected, even though it was actually negative cause the battery was reversed. All my measurements were negative but not what the drawing called for. The only way I can see me having them reversed is because I thought the battery was connected properly. Anyway I don't understand how I had the leads reversed. I asked early on in the thread where I needed to connect the leads and I thought I had them right.


You need to attach the negative lead of the DVM to ground, which in this case is the positive end of the battery (once you got the battery wiring corrected). As noted by fifties early in the thread:

fifties wrote:
S.O.P., meter negative lead on circuit ground, positive lead on each Transistor element.


If you do that, and then probe with the positive lead, you would have originally gotten a bunch of positive voltages, which would immediately indicate that the battery was backwards (which is as several of us suspected). If you do the same thing now, you will get the expected negative voltages.

No one is trying to beat up on you here, we have all done something similar or worse at one time or another. Just trying to get it straight now, and maybe check that with the battery wiring error corrected, it is indeed showing the right voltages, in addition to working seemingly correctly. I am working on a radio right now that after extensive hacking by the previous owner, and "unhacking" by me, operates perfectly - for about 1/2 hour before one transistor mysteriously overheats. So it can operate with some residual problems that still need to be corrected.

Brett


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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 1:51 am 
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below is the key. you connected the meter in accord with the reading you were expecting. That is not the correct procdedure.

In the schematic, the voltages are given with respect to circuit ground. This means that you would connect the ground lead of the meter to circuit ground. The "ground lead" of the meter is the negative. You cannot ever measure the correct polarity if you connect the meter based on what you think the polarity should be......

Yes, what you said below is incorrect.

devildog63 wrote:
No. I had positive lead going to positive terminal on the switch and since positive is ground on this schematic , I believe it correct, I used the black lead from the meter negative to probe the test points. Is that incorrect?

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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 1:59 am 
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Ok that makes sense, so even though the positive is circuit ground , I should have connected the negative meter lead instead of the positive .
Yes I was severely, grossly, terriable, awfully wrong. I think I will go hide in the conner with squires lol.

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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 2:27 am 
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Thanks once again for the help, I will double check the voltages to make sure. This thing picks up stuff new ones won't, I'm surprised at how well it operates.

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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 3:17 am 
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devildog63 wrote:
Thanks once again for the help, I will double check the voltages to make sure. This thing picks up stuff new ones won't, I'm surprised at how well it operates.


Yes, this was back in the time when a lot of people cared about AM reception. Many people don't know that FM listenership only passed AM in the mid-late 70's. And I don't think you have gotten around to aligning it yet. The antenna alignment adjustment can make a very big difference in the reception of these 7-transistor radios.

If you like this one, then try an 8-transistor type with a tuned RF section. That's another big step better.

Brett


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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 3:47 am 
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devildog63 wrote:
I don't believe this but the old battery connector was replaced by my father back in 1973. He has this crossed. I installed a new battery snap and it works like a champ.
Congratulations on finding the problem. I'm glad it is working well for you.

Curtis Eickerman

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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 3:54 am 
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Eickerman wrote:
devildog63 wrote:
I don't believe this but the old battery connector was replaced by my father back in 1973. He has this crossed. I installed a new battery snap and it works like a champ.
Congratulations on finding the problem.


The moment you figure it out, and it starts working, is what keeps us doing it! Success is very addictive.

Brett


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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 4:01 am 
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Brett_Buck wrote:
The moment you figure it out, and it starts working, is what keeps us doing it! Success is very addictive.
I like to see people succeed in doing something that they may not have been sure that they could do. Then, hopefully, they see the logic behind what they have accomplished and it translates to other things as well.

Curtis Eickerman

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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 1:53 pm 
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Yes very important thing I learned . Take nothing for granted and do it methodically. Success does keep you interested.
Thanks

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 Post subject: Re: Transistor types
PostPosted: Jan Mon 09, 2017 1:57 pm 
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Brett_Buck wrote:
devildog63 wrote:
Thanks once again for the help, I will double check the voltages to make sure. This thing picks up stuff new ones won't, I'm surprised at how well it operates.


Yes, this was back in the time when a lot of people cared about AM reception. Many people don't know that FM listenership only passed AM in the mid-late 70's. And I don't think you have gotten around to aligning it yet. The antenna alignment adjustment can make a very big difference in the reception of these 7-transistor radios.

If you like this one, then try an 8-transistor type with a tuned RF section. That's another big step better.

Brett

That's a 3 section tuning cap? With a separate oscillator transistor? I have a tube radio with that extra tube and 3 section tuning cap. Sounds like fun.

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