Pars

For the 335, you'll need dual (2x335 as shown). Are you planning on using a GRLV or the onboard +/-15V supply? For a GRLV, you can use either (depending on version of the GRLV). If your board has space for 3 bridges, you can use either a center tapped transformer, or dual secondaries. It it is only 2, then you need the dual 2x15V secondaries. You are pretty much always safe with dual secondaries vs. center tapped.

That looks like the correct schematic. The boards look fine I think, assuming that the one on the right, which is chopped off in the photo, is for -400V. Given the age of these boards, you might scan completely thru the thread to ensure there were no board errors found. I seem to recall one, which did not affect the boards that I used. Here is a schematic for the GRHV. The 900 board you have listed above is for something else (Megatron or something). Also note there is a separate GRHV thread now as well. goldenreferencehvsic.PDF

These guys have anything that you think might work? https://amscope.com/

Happy Birthday Todd!!!

Happy Birthday!!!

Happy Birthday! Have a great one!

It's more like tech flex. This is what I used what I ordered on.

I liked the sleeving I bought from a place called Titan Rig. Can't recall where I found them recommended, but it is softer than any of the parachute cord, etc. that I have gotten before.

Happy Birthday!!

Happy Birthday!!

Happy Birthday Kerry! Hope the amp business is doing well!

Hmm. So it seems pretty clear that it is something on that board. I don't recall where the tubes mount on the KGST? If they are on sockets on each board and mover with the board, then MLA's post above would be something to try as well. I would take the board out and examine all the solder connections, probably reflowing them or at least ones that look suspect. I'm assuming you have a soldering iron, etc. as from a search it looks like you built the amp? Since you are in the EU, I presume this used lead-free (ROHS) solder? Another thing you could do is take a non-conductive wooden or plastic rod or stick and poke around the bad circuit board and see if you find anywhere that effects the hum level. If so, that should narrow down an area where there may be a bad connection.

When you were checking the connectors yesterday, did you loosen the screws and reseat each wire? I presume in order to swap channels, you had to disconnect/reconnect them all? I'll be interested to see if it now stays quiet.

Someone with more experience in the stat amps should come along with some suggestions. From a general troubleshooting perspective, I presume you have checked the rail voltages and verified that they are correct? I would think they would be as biasing and the balance and offset adjustments would have been difficult or impossible if not. Given its age, I would check connections to ensure they are tight. Don't ignore the IEC ground to chassis connection. I would presume this uses those god awful* phoenix screw down connectors? I would loosen and reconnect all of those as they can loosen over time. * In my opinion. I greatly prefer pluggable connectors such as Molex, Amp, etc.

I don't have a preference and frankly never noticed it. I would guess that the previous performance was a similar layout as well. Is this somewhat at the discretion of the conductor, or is it more orchestra preference? The previous conductor was MTT who I am not a fan of.