Tracing AC signal in solid state preamp

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by stebnera, Feb 21, 2008.

  1. stebnera

    stebnera Member

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    I was wondering if there's a way to trace a signal in a solid state preamp to pinpoint the exact location of a problem. Something akin to the plate & grid probing method of a tube amp. I get the "pops" when I touch the plates & grids of the power tubes, so I'm reasoning they're wired OK as well as the OT etc. New set of power tubes, also tried a set known to be good in another amp. The guitar signal is not making it to them though, and I'm fresh out of trouble shooting ideas. I've replaced all of the transistors with new, I've been through "fresh" copies of schematics, highlighting every leg and component as I verify them & their connections, every cap in the amp is new, every piece of wire is new, every resistor checks, I'm getting what I believe to be reasonable B+ voltages...

    Aaron
     
  2. VaughnC

    VaughnC Supporting Member

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    You really need a signal generator & oscilloscope to do that properly.
     
  3. stebnera

    stebnera Member

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    I have both, if you could direct me to some instructions, I'd greatly appreciate it!
     
  4. Hacksaw

    Hacksaw Time Warped Gold Supporting Member

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    Do you mean.. direction as in, Inserting a 1k signal into the input jack from the Sig gen, and tracing the signal through the preamp stages with the scope?
     
  5. Rosewood

    Rosewood Member

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  6. stebnera

    stebnera Member

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    Thanks Rosewood. I'd only seen the tube part of the signal path chapter republished in Pittman's book. The transistor section was exactly what I was looking for!

    And I think the answer to your question was yes Rik, but specifically which points in the preamp circuit to scope. I've only just skimmed the article, have a feeling it's going to show me exactly.
     

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