Egnator 40

[SoulFetish]

Wait, wait, are we sure it's not his transformer? It sounds like he's confused about how to test, or what to expect with a shorted transformer.
Was he able to apply voltage to the primary with the secondaries pulled without excessive current?


edit: you guys ever post a reply thinking that you were at the end of a thread? Only, once you click submit, you end up on another page thinking "where the hell did page 2 come from? What did I fall asleep in the middle of this post"

[Helmholtz]

Was he able to apply voltage to the primary with the secondaries pulled without excessive current?

Yes, see post #32. Also voltages are fine with secondaries unhooked.
Problem starts when the HV winding is connected to the board. So I think we can exclude a PT fault and the problem seems to be with the HV circuit.

[Perkinsman]

Correct Helmholtz. When I remove the blue cap, can I just lift a leg?

[Helmholtz]

Correct Helmholtz. When I remove the blue cap, can I just lift a leg?

Yes.

[Perkinsman]

I lifted a leg, plugged the red HV lines in, powered up, lights came on & NO rise in current!! It slowly rose to .5A & remained there!! Ok, so the cap value is .02 uf 2KV. I’m not familiar with this type of specialized cap. When I order one, do I look for monolithic caps? Do I want to get a higher V value?

[Helmholtz]

Do I want to get a higher V value?

I would look for a quality brand (e.g. TDK) X2 (2.5kV) or better X1 (4kV) ceramic cap.

[Perkinsman]

Can you please tell me what the X1 & X2 designations mean for these caps? I have a bunch of the tan ceramic caps but none of these blue types, are the blue ones specific for higher voltages?

[Helmholtz]

Can you please tell me what the X1 & X2 designations mean for these caps? I have a bunch of the tan ceramic caps but none of these blue types, are the blue ones specific for higher voltages?

These are safety/reliability categories. Caps must be designated as X1 or X2.

https://www.allaboutcircuits.com/tec...-y-capacitors/

[Perkinsman]

Thanks for that excellent link. I found that I do have some X1Y2 caps but they are .01uf, not .02uf. Can I use it?

[Helmholtz]

Thanks for that excellent link. I found that I do have some X1Y2 caps but they are .01uf, not .02uf. Can I use it?

You may parallel two .01µ caps for .02µ.

[Perkinsman]

Thanks for all your assistance Mick, G1 & special thanks to the Dude & Helmholtz!

[Perkinsman]

Can you guys tell me why you suspected the X1 cap...and is the reason the amp would blow fuses because this cap is across the mains line & it was open causing it to pull current?

[Helmholtz]

Can you guys tell me why you suspected the X1 cap...and is the reason the amp would blow fuses because this cap is across the mains line & it was open causing it to pull current?

An open component doesn't pull current. We were looking for something shorting one of the secondaries. The cap must have developed a short across the high voltage winding. It might take some high voltage and temperature to show the short.
The Dude proposed the ceramic cap in post #25.

[Perkinsman]

Yes, I had seen his post about the cap, I just didn’t know which it was. So because it was blowing the entry & main fuses, you knew it had to be a short in the power supply so you were just tracking the power path?

[g1]

Yes, but much of the power supply is not shown on the portion of the schematic that is available. So it was some guesswork and logical inferences.
The Dude came across posts by others about the same problem with this model, the fault that they found, and showed the equivalent circuit in a Fender schematic.