Metropoulos Forum

My 1K 5 watt screen resistor on my V4 power tube keeps getting fried. I tried to re-tension the tube socket but I'm at a loss. Last night at a gig the amp would lose power from what I thought was a loose connection and I had to swap heads. Today, when I powered up the amp with the board exposed I got a lot of crackle and then clean...no crackle. When I checked, the power tube was out and the resistor was open.

The tube socket connectors feels "loose"...lots of play in their movement.

Do I need a new tube socket? Are there other causes for frying this resistor? I've replace this resistor 3 times in the 6 weeks that I've had the amp. I might just order a JMP replacement tube socket and change it.

FWIW, I put in a brand new set of "C" SEDs (EL34s) and swapped positions to make sure they were OK. I think the original EH EL34s are also OK. I don't think it's a tube problem.

Help

Clearly something is causing that spot to draw too much current, and it's specific to that tube socket. Replacing it may be a good start, sometimes when tubes blow there are carbon deposits left on the socket that can cause unwanted current flow.

So, it looks like a new socket to start...

Can I try to clean the old socket while I wait for a new socket? What would you use as a cleaner? I have "Electrosolve" residue-less contact cleaner that I use for sockets and pots. How would you clean the individual contacts?

Thanks

I suppose a pipe cleaner might get down into the sockets (don't forget to drain the caps, or that metal wire at the center of the pipe cleaner may give you a nasty surprise!!) and a small brush (toothbrush?) to try and clean the rest of the socket. I don't know if that will remove the carbon depsits if they're present though. The Electrosolve is as good as anything to try for a solvent.