marshall 18 watt trem problem

[jamme61]

I have a clone of a 18 watt marshall that I converted over the TMB side to the 1974x marshal with tremlo. I can't really hear the tremolo working but when I turn the intensity pot up, it lower the volume like a master volume? I looked over the wiring a hundred times, changed to a 5751 tube, read a million posts, any help would be great thanks.

[xtian]

Sounds like a wiring error. Post some detailed photos for us!

[Phil_S]

12AX7 is better to trigger oscillation than 5751. The tremolo requires a tube with high plate resistance. And what Xtian said.

[jamme61]

thanks guys, it was the 100k plate resistor that I didn't add when I switched the circuit over from the TMB circuit. It sounds great with the 5751 but I want to try it with a 12ax7 now that it is working. Thanks again

[xtian]

OK! No plate resistor = tube driven into cutoff, meaning zero sound, and opening the Trem pot is mixing in that cut off tube. Right?

Glad you spotted it. Imma hafta build another 18-watt soon. Likes them.

-a

[jamme61]

yes it drove me crazy but, it did cause me to clean up some wiring. I like having the trem better then the TMB, which never sounded that great. I now have a half of 12ax7 not being used.