Epiphone So Cal no blue glow!!

[Danglin' Fury]

So this So Cal's EL34's aren't exibiting the yummy blue glow we all love when we flip the amp off standby. And of course no sound from the speakers. I have the chassis out and when I turn standby off and have my meter on the power tube socket B+, it seems to be there for a split second and then not. the rectifier has somethin like 380 Volts and it is constant. I checked yesterday. I will get a more accurate measurement later. None of the fuses are blown and the large plate resistors are not open or shorted. I also get a "flash voltage" on those guys too. It looks like a high voltage on the meter, then drops down to millivolts. weird. Maybe a power supply cap?

[Jazz P Bass]

Have you tried any voltage measurements without the EL34's in place?
If the B+ is still loaded down, disconnect the output transformer plate wires.
I am really supprised that a fuse is not blowing.

[Danglin' Fury]

I have indeed tried to measure without the tubes in place. Same thing. They are also new btw. I'll try it again and then I'll disconnect the OT plate wires and try it.

[Danglin' Fury]

Just so we are on the same page here, I disconnect the brown and blue wires correct? I am assuming you've seen the schematic?

[Steve Conner]

Maybe the standby switch is faulty?

[Danglin' Fury]

Nah. Switch is ok. I think I may have found it. On the speaker out board, the black wire is glued to the board butnot soldered. Gonna solder it and see what happens.

[Prairie Dawg]

The standby is on the secondary side of the power transformer. It disconnects high voltage AC before it gets to the rectifier bridge.

It sounds like your amp is not coming out of standby. There are two fuses in there (F3, F4) because according to the schematic the standby switch lifts both legs of the secondary high voltage winding.

See if you can measure AC voltage on one side of the standby. If you cannot the chances are that either one or both of the fuses is kaput or the high voltage winding has died.

I do not think you need to lift the plate leads to determine this.

[Danglin' Fury]

I measured 715 V AC at F3 and F4 after I turned off standby. fuses are good. not open.

[Danglin' Fury]

R55 and R56 are supposed to be 220 k ohms and in circuit theyread 3-14 Meg. ??

[Prairie Dawg]

Now you know you have AC. Does it come out the other side of the switch? Where does it go? What happens before/after the diodes? Follow the power from the transformer to the place where it's used, validating your components and voltages as you go. What do r55 and 56 do? Are they relevant to this process?

[g1]

715VAC sounds pretty high, like open or unloaded voltage. Is the fuse (F8) after the rectifier diodes ok? What is the DC voltage at that fuse?
Those 220K resistors are bleeders for the main filter caps. They can be difficult to measure in circuit.

[Danglin' Fury]

Found it. F8 WAS blown. for some reason,on the speaker jack board, 2 of the output transformer wires were siliconed down but not soldered. I soldered those babies and WOO HOOO! The delicious blue glow is back. and the fuse is not blowing anymore.