The scariest amp I have seen

[glebert]

I recently bought a few project amps locally, one is a Music Man Rd 112 One Hundred. According to the guy his tech said that it was almost working but then the tech passed away unexpectedly. I opened up the amp and was terrifed by the wiring I saw. I think they were trying to convert it into a full tube amp by adding two preamp tubes and bypassing the solid state preamp. I just started cutting and removing everything attached to the tubes because it was scary.

[drewl]

Yikes

[glebert]

I didn't ask the cause of the tech's death...

[galaxiex]

Hooleeey craaap!

Looks like it was wired by a 3 year old on Ritalin.

[Leo_Gnardo]

I didn't ask the cause of the tech's death...

I'm sure the 700V power supply common to MusicMen had nothing to do with it.

[glebert]

I'm sure the 700V power supply common to MusicMen had nothing to do with it.

I certainly didn't power it up to check, but I don't think they implemented the voltage doubler, so probably only 400V or so

[Mick Bailey]

Hey, it's point-to-point, hand wired.....

[Leo_Gnardo]

I certainly didn't power it up to check, but I don't think they implemented the voltage doubler, so probably only 400V or so

I scanned around for a schematic but didn't see any. If it's anything like RD50's I worked on, their B+ was around 650-675V similar to most other MM's. Bad enough to get stung with 400V. Beyond that, if you survive the hit you'll turn the air blue, cussin' like a sailor. Works for me. Ding dangalang BLANGGIT!

[glebert]

I scanned around for a schematic but didn't see any. If it's anything like RD50's I worked on, their B+ was around 650-675V similar to most other MM's. Bad enough to get stung with 400V. Beyond that, if you survive the hit you'll turn the air blue, cussin' like a sailor. Works for me. Ding dangalang BLANGGIT!

Plate voltage on this is voltage switchable, I guess it would be 2/3 of 715V?. Here is the schematic (page 4):https://www.thetubestore.com/lib/the...-Schematic.pdf The doghouse is missing on the amp, so I need to figure out how/where to implement the rectification/doubling/filtering. I think there is enough room with modern caps to put it into the chassis rather than hanging underneath. Another option might be to use can type caps going up through the chassis where they put the preamp tube sockets. Can't use a multi-section cap with the doubler circuit though since I haven't found one that doesn't have a shared negative terminal.

Oh, and I did check the PT on a variac and LBL to make sure the voltages are right and no shorts or opens.