Crate v50 SMPS not working

[pontiacpete]

I found d104 - UF2010- is shorted and was wondering, since it seems to not be available anymore, would a UF2007 be a suitable sub?

[doctor]

I found d104 - UF2010- is shorted and was wondering, since it seems to not be available anymore, would a UF2007 be a suitable sub?

Yes, of course. He is the direct replacement (1000V, 2A, 75nS).

[pontiacpete]

Thank! Doc

[pontiacpete]

It's back. Same diode D104 shorted. It worked for 3 rehearsals. I'm not sure what to think about this. The first time it showed up here one of the 6l6's was shot along with D104, so that seemed like a reasonable enough cause for the breakdown.
So,I have a few questions with the hope that someone is still interested in helping.
This time only D104 is shorted, and the new 6L6's are still working. I replaced D104 and it fires up without a problem. The plates are at 430v and they are drawing 30ma.
My question is what, voltage should CW8 be adjusted at?
Also, since D104 is in the middle of the HV winding, does it make sense to change out C107? Could it be failing?
Or would it be a good idea to change C23 and C24? Could they be causing the amp to lose bias over extended operation, perhaps at high volume?
Does anyone have any advice here? As you can see I'm stabbing in the dark at this point.
thanks

[Jazz P Bass]

As cheap as caps are, just replace them.
Remember that late 90's cap fiasco?

[Enzo]

Didn't we just discuss this farther down the board? If D104 shorts, I'd replace the D103 and D105 in series with it.

[pontiacpete]

yes we did discuss the down a bit, sorry about that, didn't think the 'relay' title on the other post was generating any interest. Anyway thanks to you and Jazz P Bass for the suggestions I'll report back with the results..

[pontiacpete]

All the caps and diodes that have been mentioned are now changed.
I tried scoping the output to see the effects of turning CW8, this doesn't appear to change the wave at all.
Does anyone have any other ideas where this pot should be set at?

[Jazz P Bass]

I'll be honest with you. I do not have a clue.
It appears that it's function "may" be to balance the phase inverter.
I see an 82K and a 100K, like on a Fender.
The wiper of CW8 is attached to the 300 volt supply.
So turning the pot will put more or less voltage on the 100K resistor.
You would have to look at the phase inverter to see any change.

[pontiacpete]

I scoped both plates of the PI, and there is no change to the wave when turning CW8. But with the scope on top end of eac of the plate resistors, the wave changes from no wave to a small one on the 100k so I ended up turning it to the point where there is no wave since there is no wave on the top of the 82k.

[Jazz P Bass]

Kinda makes you wonder what that waveform is all about.

[pontiacpete]

Yes it does.

Thanks for all the help.
pete