Monkeymatic Shasta Princeton Reverb pine combo

[xtian]

No choke and caps are discharged. Keep 'em coming, though.

I disconnected the HT at the rectifier, leaving the heaters connected. All good.

Check out what the bulb limiter does (video attached). Bright for a fraction, then dim, then about two seconds later, very bright.

The first flash is inrush current, then it should stay dim--remember, no tubes are installed.

Suggest anything?

[JazzGuitarGimp]

I would try disconnecting the wire that feeds the screen grids, leaving all the loads downstream connected and see if the 1K still heats up. And yes, I know the tubes are not installed

[xtian]

Could this possibly be the MOVs installed on the mains? That wouldn't explain the dropping resistor getting hot, though.

[JazzGuitarGimp]

And I'm sorry if I missed it, is this build tube or SS rectified? I see a 5U4 in the Fender schematic.

[JazzGuitarGimp]

Could this possibly be the MOVs installed on the mains? That wouldn't explain the dropping resistor getting hot, though.

Correct, that would not explain the 1K heater issue, but it might not hurt to lift one leg of each of the MOV's just to make sure. MOV's usually fail shorted though, so I'm thinking the bulb limiter wouldn't dim at all if an MOV were to blame. Plus, MOV's have a particularly nasty smell when they give up the ghost.

[xtian]

SS recto. Photos on page 4 of this thread.

[martin manning]

Check out what the bulb limiter does (video attached). Bright for a fraction, then dim, then about two seconds later, very bright. Suggest anything?

Cap can.

[xtian]

Thanks, Martin. That's exactly what I was dreaming about last night.

[xtian]

Well, it wasn't the cap can. Are you ready? It is the failed reverb transformer, after all! Earlier, I had disconnected its black wire from ground to isolate it from the circuit. However, I left its red wire attached to B+, thinking, because none of it's other three wires is attached to anything, it can't interact with the circuit.

Wrong.

I believe that when it is energized with 300+ volts, it shorts to the chassis through its own metal housing! As soon as I disconnected its red wire from B+, everything returned to normal.

Much cussing followed.

[statorvane]

I've got a reverb transformer just sitting here. Took it out of a P1 eX I built several years ago. Weber unit I think. If you are interested, PM me your address and I'll pop it in the mail - no charge.

[xtian]

No thanks, I just ordered a replacement. But thanks!


Just got home from sound check at Sierra Nevada Big Room: that's my Princeton, "Sierra", on stage! Whoo!

[Milkmansound]

cool! I have played that big room before - great spot, and of course *plenty* of beer in the green room.

When I played there with my old band, they actually locked up and shut down the place with us still in the green room. We were having a good time! Someone eventually heard us and let us out.

[xtian]

cool! I have played that big room before - great spot, and of course *plenty* of beer in the green room.

When I played there with my old band, they actually locked up and shut down the place with us still in the green room. We were having a good time! Someone eventually heard us and let us out.

Ha!

They shut us down promptly at 10:30, and we had to have our gear totally out by 11pm. Pfft. Good gig for old folks, I guess. But the sound shore was nice.

[xtian]

I installed replacement reverb transformer, and everything is back to working order. I also swapped the positions of the power switch and fuse, which I had in the wrong holes. Uh, yup.

[M Fowler]

Very neatly wired looks great, where's the faceplate