[Boatanchors] Troubleshooting linear amplifier

[Bry Carling]

Yes it worked properly before OK.

It does not work properly on any band at present.

As it began to fail, it worked OK on 40m.

The ONLY way it works now, is it will DOUBLE on 40m position and produce lower output on 20m.
Not good obviously!


Subject: Re: [Boatanchors] Troubleshooting linear amplifier
To: af4k at hotmail.com; Boatanchors at mailman.qth.net; flboatanchors at yahoogroups.com
From: jwiley at gci.net
Date: Sun, 10 Apr 2016 07:03:10 -0800


  
    
  
  
    Brian - 

    

    First, I have to assume you meant "non-resonant
    PA network" as opposed to "non-resident part
    network", otherwise your question makes no sense. 

    

    If that is true, then  comes my next question:  Has this amplifier
    ever worked properly?   If not, then I might suspect that the band
    switch or some other aspect of the circuitry is miswired, either
    from the factory or after an attempted repair.  I once had a Drake
    L-4B that was miswired on 40 and 80 meters from the factory, and
    could not be tuned on either band.  

    

    If it did operate properly at one time, and has since failed, then a
    part must have failed, either completely or partially. 

    

    The circuitry in the Ten-Tec 422 is not particularly challenging. 
    First question: Does it operate properly on ANY band, when tuned
    into a known good 50-ohm dummy load?   

    

    How do you know the coupling caps are good?  Did you actually
    measure them for capacitance value, or just test to make sure they
    were not shorted?   

    

    Next, did you test to make sure the band switch is actually making
    good contact?  I have seen switches where the contact looked good
    but was burned away due to arcing so that it no longer made an
    actual connection.   

    

    Can you get drive to the amp?  Does it show grid current? 

    

    - Jim, KL7CC

    

    

    

    On 4/10/2016 6:37 AM, Bry Carling
      wrote:

    
    
      I wonder if anybody can give me any tips on troubleshooting a nonresident part network in a TENTEC Centurion 422 amplifier.

It does not seem to resonate of the right frequency. I have tried many things and is coming down to possibly being a bad band switch but how do you troubleshoot that in place?
The coupling caps are OK. The plate and load tuning caps are tuning OK. It just doesn't resonate on any band.

Best regards - Brian Carling
AF4K Crystal Co.
117 Sterling Pine St.
Sanford, FL 32773

Tel: 321-262-5471



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