Dang -- my "Simple 2A3" amplifier. Just. Blew. Up.

mhardy6647

For an as-yet unknown reason, the cathode capacitor on one channel of my (slightly modified) JE Labs "Simple 2A3" amplifier variant just self-immolated.
Big ol' pop.
Magic smoke.
Acridity.

Fug.

I am wondering if one of them big ol' Sofia "meshplate" 2A3s suffered a filament short... or just what the dang deal was.

Funny thing -- I thought that the other channel was lower in volume, and I was troubleshooting that when the fun began... but maybe the soon-to-immolate channel was actually higher in volume(?!?).

Fortunately, we do still have SE 2A3 backup at the ol' casa.

Paramours are go!

DSC_0105 by Mark Hardy, on Flickr
(photo from a long time ago...)

Thanks for letting me -- ahem -- vent

PS - I did not try the Sofias in the Paramours Tossed a pair of cheap-Jack "ValveArt" 2A3s in 'em. For now.

msg

Dislike.
Yet, like.

mhardy6647

as an aside - it was the low-volume channel that popped a capacitor; I forgot I was lookin' at it upside-down! I am not too good with spatial stuff.

bikerboy

Led Zep will do that!

agfrost

Hope you get it sorted out, Mark.

[Deleted User]

That is why you need backup SS equipment

mhardy6647

rednedtugent wrote: »

That is why you need backup SS equipment

ummm...

010 by Mark Hardy, on Flickr



The most likely "root cause", I reckon, is that the output tube on that channel shorted. I am frustrated because I don't have any means to test a 2A3 -- other than use test (i.e., plug it in another amp and see if something blows up). A shorted output transoformer's another potential cause.

I can replace the cap and start checking voltages (with no 2A3s installed).

It just wasn't something I was expecting to be worrying about this week

[Deleted User]

sorry man

mhardy6647

Well, the tubes have plenty of miles on 'em... and the caps per se are no problem to replace.
I am just not looking forward to troubleshooting

The oogy stuff from inside the eviscerated cap dissolved some of the print off the bottom terminal panel of the OPT on that side. Fortunately the other one's still legible.

EndersShadow

First world problems.... just roll in another amp and put that one to the side till you feel like troubleshooting lol....

The audio gods are saying, time to play with some other amps that haven't had any love in a while.

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mhardy6647

Affirmative, Houston. Chinese 2A3s -- but relatively good ones (the TJ/Sophia "meshplates"), as such things go.

DSC_0128 by Mark Hardy, on Flickr

Affirmative, Houston, backup amps (and tubes) are installed and on-line.



DSC_8376 (2) by Mark Hardy, on Flickr


FWIW. Here's a forensic photo of the accident scene. Trigger warning - not for the squeamish.

Simple 2A3 after the fire 08Jun17 by Mark Hardy, on Flickr

mhardy6647

I couldn't measure the DC resistance of either 2A3 (i.e., they're both at the residual level of the DMM I used, 0.3 ohm) -- so I cannot tell if one is different than the other (i.e., shorted). I don't (hard to believe though it may seem) have a tube tester that can check a 2A3!

On the bright side, the DCR of both OPT primaries is (are?) identical: 157 ohm. The OPTs seem to be OK.

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tonyb

Just goes to show...your never too old to blow stuff up. lol

ALL212

Well...after looking the picture over it's quite obvious what the issue is here.

Looks like you used a #4 star washer instead of a #6. Your flummox adapter's are both backwards and you didn't rosin up your bow.

pitdogg2

yuuup^^^^ you nailed by jimminy

mhardy6647

youse guyses is good