• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Trouble with homebuilt amp

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi all,

I am working on my first amp build and I am running into trouble that I can't seem to solve. It's a guitar amp with a two stage preamp and single power tube in the main section (shown in the upper half of the schematic). This section works great, and I am very happy with the sound. The problem is with the reverb circuit.

When I connect the reverb circuit, the amp cuts out after a few seconds. If I disconnect terminal C from the reverb driver tube, the amp recovers and plays normally without reverb.

With terminal C disconnected and the amp working normally, the top of the cathode bypass capacitor on the power tube of the main section reads about 64V. As soon as I connect terminal C, the voltage at that point drops to 0 (implying no current through the power tube, and hence the loss of output). I do not understand why this is happening.

If the amp is played at a very low volume with everything hooked up as shown, the reverb works and the output is maintained. But as soon as the volume is turned up >10% or so, the output is lost until the volume is turned back down and the power to the amp is turned off and back on.

I suspect the problem is in the way I have connected the reverb circuit. I'm sure it's an obvious problem but I am at a loss.

Thanks a lot.
 

Attachments

  • schematic.jpg
    schematic.jpg
    461.3 KB · Views: 153
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.