Peavey windsor dc heater circuit.

[Captain chunkulus]

Okay, I've never seen this and was hoping one of you amazing amp guru's could she'd some light on it fir me. Looks like they are rectifying the 6.3 heater circuit to DC. Then they run the 6.3v to pin 9 and run pin 4 and 5 to ground. I'm just trying to understand how this works.  I have read the voltage after rectification and they are getting 4.9v at pin 9 on the preamp amp tubes. The amp hums for sure and I'm wondering if it's because of the low dc hearter voltage.

[sluckey]

Tube heaters can be operated from either ac or dc voltage, but 4.9v is too low. I would suspect those 3300µF caps or one or more of the bridge diodes.

[Captain chunkulus]

Well, that was my thought as well. However, I replaced the diodes and the 3300uf caps and same result. What about pin 4 and 5 to ground? I'm really curious how this works. The weird thing is the heater  tap reads right. The power tubes and p/I all read the right ac voltage.

[sluckey]

What about pin 4 and 5 to ground? I'm really curious how this works.

Well, one side of the bridge is connected to ground also. The other side of the bridge is connected to +6.3V and pin 9 also connects to +6.3V. That means there should be +6.3V across the tube filaments.

The weird thing is the heater  tap reads right. The power tubes and p/I all read the right ac voltage.

That's not weird. It's just a clue. That means the Power transformer is OK, so the problem is either the diodes and/or caps (which you have replaced), or a bad connection between that simple diode/cap circuit and the tube pins. Measure the voltage between C21 and chassis. Should be +6.3V. If not, look for a bad connection somewhere on that bridge/cap schematic. If voltage is +6.3V, look for a bad connection between the positive side of C21 and pin 9 of the preamp tubes. Might be a couple molex connectors between that board and the tube sockets.

[Captain chunkulus]

Okay, on the Power Amp side of the Molex connector, it reads 6.2 volts ac. Once it  transfers from that board to the Pre amp board via a Molex connector  it goes down to 5.7 volts ac. At the 10n capacitor it reads 5.7 volts ac. After the diode rectification it reads 5.1v dc.at pin 9 on the preamp tubes it reads 4.87 to 4.9v dc.

[shooter]

Once a transfers

clean - re-tension the connectors, maybe even hardwire the plug/jack
sounds like it's on your DC side since 6.2ac through 4 big tubes is good

[Captain chunkulus]

Thanks, I will give it a shot. The connector is already hardwired in but I'll check the solder joints and reflow the solder.

[John]

Have you tried disconnecting the + end of C21 so that it's not connected to the preamp filiaments? Just to be sure you're getting 6'ish VDC there.

[Captain chunkulus]

Thanks so much for all the help. Turns out it was the connector. I resoldered it and the voltage came back up to right around 6vdc after the diode bridge. Tubes are getting right around 6vdc now. Seems to be working okay. Thanks again.