VTA ST-120 Ground Fault Trips

Hello,

I was playing my VTA ST-120 at fairly low volume as background music while I cleaned my office. Music Stopped. No odd sounds before then. I have one of those wall wart plug in Ground Fault Interrupters that I plug my Amp into. Noticed it was tripped. I have also retrofitted my ST-120 with a three prong plug, ground going to chassis. Turned off the amp, reset the GFI, turned on the AMP. Tubes started to glow, and when the Time Delay Relay turned on power the GFI tripped again. Voltage going in was about 119 V on the KillaWatt display. I keep the bias at about 0.45, probably checked it two weeks ago. I use a Tung Sol 5AR4 for rectification -- I do have some copper top kits on hand to assemble. I plan to test the GFI on some other grounded item, but I was wondering if there was anything obvious I should look at on the amp.

This is from the tubes4hifi page referring to the TDR:

"This board is to be used ONLY for solid state rectifiers. If used with a TUBE rectifier, the TDR can cause problems with the normal slow warm up of the tube rectifier and may damage a tube rectifier. If you intend to use a TUBE rectifier ONLY with your amp, you do not need the TDR. If you do use a tube rectifier with the TDR, you should BYPASS the TDR. Instructions are included with the TDR on how to bypass the TDR."

I also use those GFCI devices around the house and once in a blue moon they can be a little touchy. I think trying the solid state rectifier would be a good idea.

Caveat: I'm not a tech.

Two things that need to be addressed.

1. Remove the TDR if you are using a tube rectifier. It is designed for solid state rectifiers to prevent damage from applying full voltage to the tubes with cold cathodes.

2. These older style vacuum tube amplifiers and GFCI typically do not get along. I have always put my tube amps on circuits without GFCI.

I have an ST120 with a TDR and I use a tube rectifier (Tung Sol) and also use a GFIC. I have no issues and have operated it this way for about 3 years.