Bridged two Metal Can Cap prongs...what did I break?

[LustandFury]

I was testing the voltages on my old projector amp-to-guitar amp conversion and accidentally touched my multimeter probe across two of the caps prongs. They were really close together and it was in a awkward place. There was a small spark but then the amp started humming really loudly. Did I blow one/or both of the in the filter caps? or something else? nothing seemed damaged around the outside of the cap so I'm guessing it's the inside. The can was the smaller one on the left...
http://photos-b.ak.facebook.com/photos-ak-sctm/v130/60/104/638785631/n638785631_1448441_9441.jpg

[Blue Strat]

When you created the temporary short, you may have taken something else out like a resistor (unlikely) or a tube. Let the caps discharge and check resistor values. Then swap in known good tubes.

[LustandFury]

Ah thanks. I'll try that. Would it most likely be one of the preamp tubes?

[Blue Strat]

Ah thanks. I'll try that. Would it most likely be one of the preamp tubes?

I can speculate all day and be wrong. You can take 2 minutes and find out the real answer ;)

[LustandFury]

Yeah I'm just at work and bored. I have to wait till lunch to try.

[LustandFury]

Well it seems to be the EZ81 rectifier. It's the only one I don't have a replacement for and it's the first tube the one Cap sees. All the other tubes don't seem to effect the hum. I also can't get any signal coming through when I plug in my guitar. Does that seem like it sound like the EZ81 to to you? I'll have to go out and get a new one I guess to find out for sure. :(

[WaltC]

If you don't have another EZ81 to put in place, then you can't know whether it's the problem. When you pull the rectifier, you shut off all B+ voltage to everything down stream from it and the amp won't make any sounds. This is true whether the EZ81 was part of the problem (I'd bet against it, just my experience talking) or not.

Can you determine whether the hum you have now is 60 cycle hum (bad filtering, damaged filter cap, what you inadvertently shorted) or 120 cycle hum (filament induced hum probably).

If you have the patience you can disconnect the two terminals in the cap can in question and sub in externally individual filter caps of like voltage and mF and see if that fixes the problem. If it does, you can put in the individual caps if you have the room and don't what to mess with replacing the cap can, or order a new cap can (Antique Electronics Supply, Ted Weber, etc.) and swap it for the damaged one.

Careful, you're messing with 300+ DC volts working in there (remember that short <G>?) and amps like that are problems to work on because of the cramped space and the "vintage point-to-point" wiring <G>. And remember, caps can hold charges a long time if they're not properly discharged, and can even recharge themselves when not connected to the wall!

[LustandFury]

Thanks for all the info. I discharge the caps whenever I touch it and check voltages a million times until they are at zero. I had it on because I replaced the 2 prong chord and wanted to make sure everything was working so I was testing the voltage coming off the caps to see how they were running because of the age...all in the 300+ range. But the space was so cramped that I jumpered the two prongs.I'll have to take the cap to replace it because the the voltage info is on the other side of the can :[