Current problem with a 6534+

[rblp]

I have a Peavey 6534+ head. The V8 power tube socket draws more current than the other three sockets. I say socket because when I move the tube from V8 to any other socket the current drops by a little over 10ma. So one tube is showing 32ma and the other three from 19ma to 21ma. When I remove the outside tubes the current is close on the two remaining tubes. This is the 3rd set of tubes that has done this. I’ve replaced the 700 Ohm 5W resistor connected to pin4 and the 2.2k resistor on pin5. I re-soldered all the solder joints connected to that socket. I can’t find anything else that is exclusive to V8. Does anyone have any ideas of what could be wrong?

[Enzo]

See if pins 3 and 4 are shorted together on that socket. Use a meter.

[rblp]

See if pins 3 and 4 are shorted together on that socket. Use a meter.

Thanks for replying.

Pins 3 and 4 show 2MOhms and it is decreasing slowly. I got the same reading on another socket. You got me hoping that my socket was bad so I stuck a lead in the socket hole and the other to the connection on the PCB. Each pin is making a good connection to the PCB.

I also checked the voltage (AC and DC) of each pin of 2 sockets and they were the same. Except Pin 1 of the bad socket was 0vac and the other 124vac. I thought those were not connected.

The amp seems to work perfectly with 2 tubes in it. When I put 4 tubes in it has a slightly louder hum, but it's always done that (it's not a bad hum).

[g1]

How are you measuring that current? Are there cathode resistors used for measurement? Could that one be out of spec.?

[Enzo]

It was just a thought, one way to make one socket different.

Imbalance in the push pull will cause hum - rather it destroys the hum cancelling of a push pull stage. If V8 is off from the others, then leaving it as an empty removes it from the equation.

If any tube shows X currrent in three sockets and 50% more in the last, then we would tend to think something about that socket is funny.

Pins 1 and 8 of all four sockets are to be wired together. Power off and discharge things, unplug from wall, then measure resistance between pins 1 and 8 of the bad socket. COmpare to the other three sockets. Got open?

Pin 1 is not connected on 6L6 tubes, but it MUST be connected on EL34 tubes. That is the primary problem converting a 6L6 amp to EL34.

Remember to count pins correctly. Clockwise from the notch from below, and counterclockwise from the notch up on top. However, pins 1 and 8 are either side of the notch, so it is hard to confuse.

I won;t respond anymore to this in the Peavey forum, I don;t want to have two conversations. This board is more about repair work, and more tech guys hang here.

[rblp]

How are you measuring that current? Are there cathode resistors used for measurement? Could that one be out of spec.?

I have a bias probe from eurotubes and I move it from socket to socket.

[rblp]

Pins 1 and 8 are open on that socket only. The schematic shows a trace on the PCB primary side, but it's not on my PCB. I can see the connection on all the other ones. I'll tie them together and report back.

[rblp]

That was it! I checked every socket and tried different tubes in V8. They ranged from 21ma to 25ma. I can live with that. The hum is way better and it sounds amazing (of course I always thought it did). I would never have thought they left a trace off the PCB. It wasn't cut or broke, it just wasn't there. I bought this within a year of them coming out so this must be a remnant from the 6505+ board that didn't need to connect pins 1 and 8. I wonder how many more 6534s are like this.

Thanks so much for your help!

Bryan

[tedmich]

Glad its working now Bryan! Check this ancient thread
http://music-electronics-forum.com/t29988/
I was wondering what the differences were on the power amp PCB between the 6505+ and the 6534, it was that trace between pins 1/8 on V8! Either PV installed the old 6505+ board or yours was replaced with one maybe?

I gotta get another board from Peavey as I just inherited an old 5150 with a PA board "issue"