Rocket voltage issues

[JoshBernstein]

A few months back i finished up a rocket-esque build, and it sounded very good for a while. I went to play it last night and it just sounded off. The distortion had this weird, gross artifact in the high end, something i havent heard before. I checked voltages and they are very strange. The power tubes have about 340 volts on them and the preamp voltages are low. The input tube was around 90 volts if i remeber correctly. I only checked quickly, but i will make up a full voltage chart this afternoon or tomorrow morning. Does anyone have any suggestions or ideas for this? Also it should be noted that i am using a solid state rectifier, and i did try a tube swap without any improvement.

[dorrisant]

Did you try another set of power tubes? I've had weird distortion pop up as a KT66 went bad twice on the same Rocket based amp.

[Mark]

My Rocket has between 310 and 315VDC on the centre tap of the output transformer.

[kutless84]

I know this post is pretty old, but I recently just finished a Rocket build and seem to be having the same issue as the original post, about 90v on the preamp. Anyone have an idea?

Jay

[Mark]

The first pre-amp voltage in my amp was lower than expected. I found I had a small DC voltage on the grid of the first valve. This caused the pot of my Les Paul to sound scratchy, the fix was to find a valve that doesn't get DC on the grid or put a 0.047uF cap in series with the input. This will mean relocating the 1M grid leak off the input jack as the grid of the valve will be effectively decoupled from it.

[guitarmike2107]

I know this post is pretty old, but I recently just finished a Rocket build and seem to be having the same issue as the original post, about 90v on the preamp. Anyone have an idea?

Jay

90v on the valve pins or 90v volt at the filter cap?

Use Ohm law to figure out where the currents are flowing in the amp and then adjust the resistances to get the voltage where you want them all.

One trick to get the voltage higher on the input valve to to feed the last filter cap stage (B4) off the B2 filter stage, missing out the voltage drop from the B3 filter cap