Tube Amp Archive

Watch out with that low bias voltage on those tubes! With anything over 450 on the plate and 300 on the screen you want closer to 37 volts coming in on pin 5. Yeah - I got a bias Tube scout from TubeDepot for this and future use - the bias is actually closer to .039 on V8 and .038 on V7 so I think ...

Tracked down channel 1 hum to the volume pot. Re-cleaned it and replaced the 100k resistor and then re-flowed the solder on all the connections. Now it sounds great - the hum is still slightly there but it matches channel 2 and is probably as good as it going to get. Going to try to get the reverb r...

Checked the the wiring in the voltage doubler stacks and the positive side of C27 was mis-wired and that's where the voltage drop was. Now it's back to about 475V. I knew it wasn't the Cap can C25 - I replaced all those. Also I put in a 3-wire AC cord and removed the unnecessary death cap and ground...

Question, on V1 what's the 1M across the input and pin 6 do? Actually it's there in the original - however the re-draw shows a 1Meg going from hot to ground on a switching jack. Creates a high and low gain input across the 2 jacks. This is explained in an article from Vintage Guitar "ᦙ...

Micajah wrote: On the output tubes V7 & V8 pins 3 should have 475v its 480.

Sorry - Typo -...pins 3 should have 475v its 380

Started checking voltages - here's what I found. Voltages on pins 1 and 6 of preamp V1 should be 100 - pin 1 is 74v, 6 is 134 on the Rectifier array the B+ should be 480V, its 370V On the output tubes V7 & V8 pins 3 should have 475v its 480. I've attached schematics - the original from the manual an...

OK - tracked the motor boating problem down - When I bought this amp it was missing the OT. And it was obvious that someone else had done some fixin' - some of the caps were already replaced etc. I ASSumed that they were all replaced correctly. Well on V1, the electrolytic between the cathode pins 8...

Ok- retensioned and cleaned the 9 pin sockets - got rid of the snap crackle pop but Motorboating is still there. Moving on.

That's what I was thinking. I tried retensiioning and cleaning the sockets and pins. I had to replace one of the 9 pin sockets already because of bad solder pins. I may have to start replacing the others. I'll try the procedure you suggested to see if it will help. Thanks

Swap the blue and brown OT leads on pin 3 of each output tube and see if it gets better or worse. You can also swap the two OT primary leads if thats easyer. Yeah - didn't seem to make a difference. on the volume knob If 7:00 is 0 then it starts oscillating at 9:00. Als o noticed something else - I...

Structo wrote:Does this amp have grid stoppers on the power tubes?

I don't think so - here's a re-drawn schematic that i found elsewhere.

Swap the blue and brown OT leads on pin 3 of each output tube and see if it gets better or worse. You can also swap the two OT primary leads if thats easyer. Thanks for the responses. I'll try the OT Lead swap but this amp doesn't have a feedback loop so I don't think it will make a difference. But...

Motorboating Silvertone 1484 Trying to finish my 1484 refurb. When I got it it was missing the output transformer. I replaced it with a new Weber 1484 direct replacement transformer. I then replaced all of the electrolytic caps including the multi can (re-stuffedit to save space) and the drifted res...