[NJARC] Re. Sears guitar amp

[Chuck]

Yes that sounds familiar!
I will check that out.
THANKS!!!
Chuck

From: Bill Zukowski 
Sent: Thursday, January 12, 2017 12:54 PM
To: Chuck ; njarc at mailman.qth.net 
Subject: Re: [NJARC] Re. Sears guitar amp

Chuck,

Just talking to a friend (previous NJARC member), and mentioned your amp issue.  He remembered Danelectro was making amps for Sears.  You may want to pursue that path.

Bill


On 1/12/2017 12:02 AM, Chuck wrote:

  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 mailto: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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