Tube Amp Archive

Update... Replaced the 150 ohm/10 watt cathode resistors with a couple 200/10. I also have a pair of 250/10, but tried the 200 first since they have to same form factor as the originals. I also swapped out the original Siemens 50uF 50V filter caps for a pair of CDE 50uF 50V caps (though the schemati...

Edit: nevermind, the 150 ohm resistors are the big ol' white ones staring me in the face... Those 150 ohm Rks should be moved up to between 200 - 250 ohms to get the bias about right. I see the 35/50 Siemens caps on the schematic and in the picture, but only see the 150 ohm resistors on the schemati...

mbeldyga wrote:I didn't even looked a schematic. My bad, sorry for that. It's cathode biased indeed, so about 1V looks fine - check voltages with schematic like Cliff Schecht said. Your bias caps are in place i belief. These silver electrolytic near to chassis's top.

no problem...appreciate the help.

Your amp is cathode biased. In the schematic I see two 150 Ohm resistors in parallel with 35uF, 50V capacitors but in your pictures I do not see this capacitor. Add this in and also, for safe measure, you probably want to recap the entire amp (just the electrolytics, not the ceramics/others). Once ...

not really topical, but here's a pic of the reverb tank label.

[img718]http://img683.imageshack.us/img683/8169 ... bplate.jpg[/img]

Take power tubes out of their sockets and check what's voltage have you got at pin 5 of each 6l6s. This is your bias voltage which should be negative (respect to ground) I pulled all the tubes (preamp, power, and reverb) and measured across pin 5 to ground (chassis) and got 1.12 V across all the 6L...

Structo wrote:I circled pin one of the tube with a yellow circle that you can drain the caps through. Look at the full sized picture below by clicking on it....

Thanks *very* much. Caps are drained.

hmmm...where to start? you should be able to click for a full size image...

[img1345]http://img684.imageshack.us/img684/2599 ... 1aguts.jpg[/img]

Yeah.......don't do that! You need to check things well, before you power that up again......... definitely some problems there. Bias is out. Check resistors, diode, and grid leaks. If you have worked on high voltage amps before, you should know what to check. If not let us know, and we will walk y...

Just got this old 4x6L6 Montgomery Ward head and the tube plates are looking pretty hot. Is this what is referred to as "redplating"?

[img:920:690]http://img228.imageshack.us/img228/6214/redplate.jpg[/img]