Not a good start...

[Magnatron]

I built a Hoffman Princeton Reverb and went through the startup testing procedure today following https://robrobinette.com/Tube_Amp_Startup.htm. I did several point-to-points on the board and wiring connections. I then used a variac connected from a light bulb limiter to form the filter caps, then removed the variac and connected straight into the light bulb limiter. I did my voltage tests and everything looked good with the rectifier, then with the preamp tubes installed. Then I installed an 8 ohm dummy load and the power tubes (6V6). Everything checked out properly. I switched out the load and went into an 8ohm speaker, removing the light bulb limiter. The attached file is what the sound was like through the speaker after turning on the standby switch. The sound is there with and without a guitar attached. The guitar does not sound through the amp when strummed. I'm a little in lost territory what to look for and check. Can someone give me some ideas?

[martin manning]

Try disconnecting the negative feedback and see if that stops. If it does, reverse the OT primary wires.

[Magnatron]

Thanks Martin. Unfortunately, we had a leak pop up in our house that's taking priority and I'll be traveling the next couple of days. I'll test it out later this week and drop a line back with the results. Thanks for helping!

[Magnatron]

Try disconnecting the negative feedback and see if that stops. If it does, reverse the OT primary wires.

Martin, I finally had a chance to try it and you were right. Swapped the OT primaries and everything seems to work and the sound went away. Have some 60 cycle hum I need to sort, but thanks for the help!