Tech Help: Clipped Signal

marl3y

Member
Need a bit of help identifying the cause of clipped signal in the "Lead" channel of a Peavey Classic 50. Have it narrowed down between the 2nd and 3rd stages. Signal looks fine out of the coupling cap (green circle), but missing nearly half of the sine wave out of the voltage divider (red circle). Here is the schematic with the reference points identified and the corresponding scope traces. Have checked the resistors and pulled the cap, same result. Also have disconnected the B+ supply from the 3rd stage, in case some sort of interfering signal was coming back through the grid, also no difference. Thanks in advance.

Edit: Updated to include preamp voltage readings. VDC ground referenced, except drop across RP.

Edit2: Signal readings added. Vpp readings with a 1KHz 2.0 Vpp input signal. The "Dirty Pre" pot is set half way. Clipping problem is worse as this is turned up. So, the input into V2B needs to be reduced something on the order of 20X. This amp appears to be stock, so seem likely that something has failed, resulting in this phenomenon. Possibly even at the input to V2A, is 2.9 Vpp too much? Happy to take other measurements, and appreciate the help. Thanks.

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Sorry for the delay. It was, but even when out of the circuit I still had the problem. Ultimately I resolved all this by replacing the pot. Tested fine out of the circuit, but for whatever reason when I put it back in it failed. Confounding, but at least the trouble has been corrected.
 
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