Capacitor voltage question Musicman HD120 2KV cap!

[nsubulysses]

Maybe this is an anecdotal experience but I've had three Musicman HD130s in for repair and two of the three have had the .001uF/2000V capacitor from EL34 anode to ground shorted. This of course blows the mains fuse once you flip the standby.

I am unable to find a .001/2000V cap at mouser or digikey and a tech friend is saying 1000V is "way plenty." He has repaired a billion more things than me so I am inclined to take his advice, but if this is the case why do the 2000V short, and why have I seen this on two out of three HD130 repairs??? Anyone else come across this scenario?

Can someone please correct my typo in the thread title to read "HD130"

[52 Bill]

I've seen that same cap short before. Could be a bad run of caps or really too much voltage spike from the output xformer.

It would be interesting to see if the ones that have shorted were all from one time period/batch or not. I think that I've used 1.5kV ceramic caps there with no known problems.

[g1]

Did you search for 1000pF 2KV? Lots at mouser & elsewhere, ceramic or film.

[nsubulysses]

Oh thanks. i was scrolling through their search menu having poor results buy typing that in yeilded many options

[loudthud]

Many more parts found with 3KV rating. Some of the searches got more results with 1nF or 1000pF.

[J M Fahey]

just 1000V is not enough.

Maybe your friend thinks "600/650/700V +V ; so 1000V is ample".

Thatb is true ... at idle; at clipping it's twice as much, and more so with peaks and overshoots, so 1500V is really the minimum.

[nsubulysses]

Thanks for clarifying. I ordered the 2000V cap from Mouser as I do tend to trust my tech friend, but I trust Leo and Musicman (and you all) more. Plus, since the 2000V caps still fail somewhat regularly I am reluctant to go with a lower value.

[52 Bill]

...but I trust Leo and Musicman more.

Leo had nothing to do with that decision.

[nsubulysses]

I thought he designed these amps as a "silverface twin reverb killer"

Maybe I just read that somewhere and an untruth has been perpetuated

[52 Bill]

Leo had a completely separate company set up to build the guitars, which he supplied to MusicMan. Tom Walker had control of the amps and Forrest White helped to run the company.