[NJARC] Re. Sears guitar amp

[Chuck]

Hi William,
Thanks for you help...
I removed the PNP and NPN power output transistors (one each) and tested 
them with a transistor tester and they both read good.
In fact, I have tested every transistor, all the Ecaps and most of the 
resistors, and replaced all that were too far off, plus took a few voltage 
readings that looked okay. But I couldn't really know because I don't have 
the tech data - ugh...

Thanks,
Chuck
AC2DP

-----Original Message----- 
From: William S Zukowski
Sent: Wednesday, January 11, 2017 4:37 PM
To: njarc at mailman.qth.net
Subject: Re: [NJARC] Re. Sears guitar amp

Just remember
Reply = Poster
Reply All = Everyone

_________________________________________________________
That's "....analog VOM using the diode test range."

Bill
Sent from my iPad

> On Jan 11, 2017, at 16:23, William S Zukowski <n2yeg at optonline.net> wrote:
>
> Just remember
> Reply = Poster
> Reply All = Everyone
>
> _________________________________________________________
> Sounds like a shorted output transistor.
>
> Is the hum still there with the volume control at minimum?
>
> If you can determine the output transistors' leads, measure the voltage 
> across the emitter - collector leads of each transistor.  The output 
> transistors act like a voltage divider, so you should measure 1/2 the 
> supply voltage across each transistor.  A shorted emitter-collector will 
> have 0 voltage across it, and the other transistor will have full voltage. 
> However, if it's a base-emitter or base-collector short this method may 
> not be conclusive.  The best way is to remove at least 2 of the 
> connections and measure the resistance between each junction.  Do this 
> with either an older analog VOM or using the dio
>
> Hope this helps.
>
> Bill
>
> Sent from my iPad
>
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