Just Smoked the QUAD cap in my Sceptre

[MrCreosote]

Amp hadn't been used in about 10 years.  I hooked it up and wasn't getting any output.  Wiggled connections and thought it could have been dirty pots or jacks since was getting output while wiggling/twisting stuff...

Then "Phfssssssssssst... with some sputtering sounds and then SMOKE pouring out the input jacks.....  I think I turned it off before it was done frying...

Touched all components.  Nothing was hot EXCEPT for the Quad Cap - quite hot it was.

Pulled the chassis and found some tar-like excrement on a couple of the terminals from the QC and a "shinny oil" on the resistors connected to the QC.

I'm pretty sure it was the QC but what really bothers me is what else might have been destroyed?

Any thoughts?

I've done some limited electronic repair on amps and tv's so I'm probably going to give this a try.

Tom

[loudthud]

There is no available replacement for that cap that can withstand todays line voltages. You really need something with a 600V rating. What I do is build a small circuit board with eight caps, two in series for each section of the old can cap. There are kits available on the internet that were made to replace those caps in Dynaco amps.

[MrCreosote]

yeah, I saw the board replacements for the Dynaco stuff.

As far as where to put them - I suppose there are lots of ways.

It would be nice to save the original "look" of the can I suppose...

Do you tuck everything in the chassis or mount something topside?

The big question is did I damage the transformers.  That's the $285 question ( or thereabouts.)

Thanks
Tom

[basiklybass]

I disconnected the old cap and just left it. Installed the new ones in the chassis. Used terminal strips from Radio Shack and riveted them to the top of the chassis.

[MrCreosote]

Just found a crusty mound of secretion from the separate 20uf 600v that is connected to the standby switch.

I think I might hollow out the can and maybe I can stuff a couple caps into the can to same room under the chassis.

[MrCreosote]

Lots of interesting surfing URLs of tube amplifiers, antique capacitors, and Frank...  and Antique Electronic Supply.

Faced with 3 solutions:  (All solutions involved replacing the big 20uF, 600V hung off the stanby switch with an Atom.)

1) replace can w/new can from AES,,
2) replace can w/4 Atoms,
3) replace can w/series pair electrolytics.

A lot of places don't like the series pair because there is no way to be sure that the voltage is split between the 2 caps evenly - so they use load balancing resistors (a small resistor is placed across each cap so that there is now a resistor dividor which balances the V across the 2 series caps.)

AES says the new cans are made with the very same Mallory machines that made the original Dynacos.  (I guess Mallory made cans for C-D which is the manu name on my smoked cap.

BTW, I finally came up with the best description of what the cap failing sounded like:  a Roman Candle (!)

[basiklybass]

http://www.tubesandmore.com

Yep, this was the one I found that is supposed to be the same as the original. I do think tha amps sound better and stay clean at higher levels with the increase in the first two stages.

[Soundmasterg]

When the caps go bad like that, the thing that could fail would be the power transformer, and that is due to too much heat. Since the bad caps are conducting too much current to ground, the power transformer tries to supply more current than it can, overheats, and shorts. Usually you'll see wax on the transformer if this is the case.

Its always a must when using series connected caps to also use a paralleled 220k 1w resistor with each cap. See your other post for more.

[basiklybass]

Yep, that's what I found with mine. Put in the Triode....works like a charm.

[Isaac]

I'm amazed that no one asked what kind of rolling papers he used.

I need to start hanging out with serious people more often.

[basiklybass]

Arr...Arr...Arrr...good one.....but was it smooth and mild?

Mine is smooth and mild...up to about 7...then it gets a bit harsh......and I am filled with the spirit of Jack Bruce....no wait....I think it's Patron I'm filled with.......it's some kind of spirit.