Tube Amp Help!

[DalyTek]

OK, I was installing new pickups in my son's guitar and had a hum from the neck pickup only so I went to recheck my wiring and found a loose connection.
Went back to the amp and have no sound. The amp is a Crate Vintage Club 50 half stack.

I tried it on my amp, worked fine. Tried his cab and his cable on my head, worked fine.
There is no sound at all from his amp. No hum, no hiss....nada. Both of the A/C power lights are lighting up.

I opened it up and checked the fuses. Both are fine.
All 8 tubes are glowing as they should as well.
I do not have any extra tubes to test with, but I did swap their locations around.

I think I found the problem. There is a visibly bulging capacitor in there.


I have replaced capacitors before, but not in anything like this. This is a fat capacitor with a 10000uF/16WV rating.
How do I go about replacing this cap? How do I drain it?

Is there anything else I should check for? Any help would be GREATLY appreciated!!

[RacerX]

The amp is a Crate

I think I found your problem.






J/k - couldn't resist

[straycat]

Club 50's sound pretty nice plus I have never had a Crate tube amp that didn't sound pretty good.

[DalyTek]

Its a great amp and I really need to get it working again for him. Anyone know how to fix it?

[Amerturk]

OK, silly question but did you check the speaker connections? Does it work with an external speaker/cab?

[Cygnus X1]

Here is the schematic.

http://www.blueguitar.org/new/schem/misc_amp/crate_vintage_club_50.pdf

I don't have time to figure it all out but you will see that cap C57 value coming off the transformer/power supply.
It has a test point value you can check.
I hope you are comfortable working inside tube amps!

I have nothing to base this on but I suspect a cap value like that has something to do with a channel switching
scheme.

[DonP]

This is a fat capacitor with a 10000uF/16WV rating.

The 16 volt / 10000uf capacity rating indicates is is used for low voltage power supply filtering, solid state stuff like channel switching, but could also be used as a DC source for preamp tubes to lower noise(nope). After looking at the schematic, it looks like effects loop and reverb are SS, so it likely power both of those.

How do I go about replacing this cap?

You need to be able to get under it to de-solder it.

How do I drain it?

Draining any capacitor is the same. Use a power resistor (10w 10K) with a couple of clips. Connect the clips to the ends of the cap to drain the stored energy. I'd also be worried about the higher voltage caps also found in the amp. Anything large should be drained.

Is there anything else I should check for?

That cap does look bad. Hopefully that's the only thing wrong.

[DalyTek]

OK, silly question but did you check the speaker connections? Does it work with an external speaker/cab?

It's a half stack, so I have to use an external cab. I did check the cab and the speaker cable though.

DonP, thanks for all the info. I need to try to track down the appropriate replacement capacitor now.

[straycat]

Hope you get it fixed up, really nice sounding amps.

[Cygnus X1]

Good post DonP.
You're my official clean up hitter.



I had to run out the door to go to work but wanted to share the schem while I had it in mind.