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 Post subject: Help transistor doing the craziest thing video attached
PostPosted: Dec Tue 05, 2017 4:15 am 
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Joined: Apr Tue 07, 2015 2:36 am
Posts: 235
Location: Waterford MI
Can you guys have a look at this video If I put my finger on the transistor Nte160 I get a great Fm signal but it I take it off I get nothing. Confused Help ! :)

https://drive.google.com/file/d/1KQdHEdHGKd66eVeo9FE6csWKvEkuQk4s/view?usp=sharing


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Tue 05, 2017 4:28 am 
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Location: Creswell, OR.
Is the can of the transistor connected to the collector? If so, is the collector of that transistor getting the proper biasing? What is the function of that transistor in the circuit? You don't happen have a schematic of that section of the radio by chance? My wild guess is that you're giving that transistor's collector a slight negative bias by touching it, causing it to behave ... err ... correctly? or at least differently.

- Scott


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Tue 05, 2017 5:05 am 
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Joined: Apr Tue 07, 2015 2:36 am
Posts: 235
Location: Waterford MI
I just shot a quick pic of the section in the schematic its Q1 upper left

https://drive.google.com/file/d/1mjakJd1tUTVrQimpTpb-ug8PWtCcR4BN/view?usp=sharing


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Tue 05, 2017 6:08 am 
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Joined: Apr Tue 07, 2015 2:36 am
Posts: 235
Location: Waterford MI
Also I noticed if I pull the transistor out and barley make contact with it the fm will jump in and play but if I push it all the way in I get nothing but static. I did use contact cleaner and cleaned all contacts real here well.


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Tue 05, 2017 6:14 am 
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Joined: Jan Thu 01, 1970 1:00 am
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As the FM RF amp it would have everything to do with signal. Since you have the print, try taking voltage measurements, and post both them and what they should be (print's too small for me to see the digits).

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Tue 05, 2017 7:51 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Las Vegas, NV, USA 89052
Might wanto closely examine the soldering on the transistor socket or even just heat the solder to reflow it.


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Tue 05, 2017 5:15 pm 
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Joined: Jun Sun 15, 2014 11:04 pm
Posts: 759
Location: Coos Bay, Oregon
It is possible the signal path is disconnected before that transistor, preventing the RF from passing to that transistor. You touching the case of the transistor would then be introducing an antenna. There are lots of things you can do: Test the antenna coupling coils for continuity, check the bias and supply voltages on that transistor, inject an RF signal all along the signal path before the transistor, follow the signal path with an oscilloscope. Those are just a few of them.


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Wed 06, 2017 12:27 am 
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Location: Black Hills, SD 57745
If it's a contact thing, pushing on it with the eraser end of a pencil would do the same thing as your finger. If it's your body capacitance acting on the circuit, just barely making contact with your finger would make it change. I'm going with flaky socket, soldering or faulty transistor. Might take more than just a spray of cleaner, the socket's contacts may be weakened or oxide on it or the transistor leads.

-Ed


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Wed 06, 2017 12:35 am 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: The Old Dominion VA 23518
NTE160 has 4 leads - do you have all connected correctly? If only using 3 leads, do you have the E-B-C pins connected correctly?

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Brian
"Capacitor Cosmetologist since 1979"
USN Retired 1984-2006 (Avionics/Cal)


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Wed 06, 2017 12:35 am 
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According to the schematic, the case of he transistor is grounded. Can you see how that happens?

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"It's always something". --Gilda Radner (1946 - 1989)


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 Post subject: Re: Help transistor doing the craziest thing video attached
PostPosted: Dec Wed 06, 2017 2:57 am 
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Joined: Apr Tue 07, 2015 2:36 am
Posts: 235
Location: Waterford MI
I'll work on getting those voltage tested. The transistor is brand new and behaved just like the old one. Pretty sure I got it installed correctly. The socket as you can see is connected to the metal box. Would I have open it to get behind it and to re-flow or make other tests of the circuit. Do I just un-solder it and have a look?


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