My Marshall Blew a Filter Cap!

[Dai H.]

i thought they were supposed to give out there so the entire cap doesn't blow up. Saw a guy's old JTM45 on the web once which had a failed electro. The whole thing blew up and left a big mess inside the amp. Newer electros iirc were designed to give out on one end to let out the built up (gas?). Like on small radial electros there is a sort of cut on one end which I think was a purposely made weak spot in the casing.

[Paul Marossy]

i thought they were supposed to give out there so the entire cap doesn't blow up. Saw a guy's old JTM45 on the web once which had a failed electro. The whole thing blew up and left a big mess inside the amp. Newer electros iirc were designed to give out on one end to let out the built up (gas?). Like on small radial electros there is a sort of cut on one end which I think was a purposely made weak spot in the casing.

Oh yes, that is absolutely correct. I was just saying that the exposure of those caps for roughly two summers of 140-150 deg F heat in a garage and an average relative humidity of only 10-15% all year round, I think it may have aged that rubber piece "beyond its years", and that may be why it blew, not so much because it "lost its form".  :wink:

[R.G.]

I also noticed that two of the other caps have a small bulge in the same area as that one that blew.

What might we infer from that small bulge?

[Dai H.]

right, might want to replace them all.

I think these LCR type caps are the ones to be really cautious about. Shocked

mm...I think it's more the non-use and conditions they experienced more than the type of cap. Example, I've got LCRs in a '88 50W Marshall (still the stock caps), and they work fine.

[Paul Marossy]

Oh, don't worry guys, I replaced them all.  :wink: