Tube Amp Archive

I could change the 56k to a larger resistor, correct? Would that drop the bias?

angelodp wrote: ↑Sun Jul 07, 2024 11:01 pm You could implement the adjustable bias mod that Rob R has on his site. In that way you can dial in the bias current you need.

I may try that. Thank you!

Privatpig wrote: ↑Sun Jul 07, 2024 4:22 pm

Stevem wrote: ↑Sun Jul 07, 2024 1:08 pm If your output tube bias voltage on pins 5 is still only -45 then that’s why the amp is very loud and also more distorted then it should be.

Your also going to be eating up the output tubes very fast.

I will check it when I get home! Thanks again!

-53.8 and - 53.6. What shouzld I do now?

Stevem wrote: ↑Sun Jul 07, 2024 1:08 pm If your output tube bias voltage on pins 5 is still only -45 then that’s why the amp is very loud and also more distorted then it should be.

Your also going to be eating up the output tubes very fast.

I will check it when I get home! Thanks again!

Are those Voltage readings you took in the layout picture of post #1 ? Check connections around the middle preamp tube. Is pin 1 connected to pin 7 ? YOU SIR NAILED IT! AND SOMEINE ELSE SAUD THEY BET ITS IN MY PREAMP TUBES! THANK YOU GUYS! YOUR ALL AWSOME!! So I got to looking at the drawing and on...

Mains power OFF Ohm checks: 1) Verify that the input jacks are wired correctly. Plug a guitar cord into one of the inputs. Measure Ohms between the sleeve and tip of the other end of the cable. You should measure either 1 Meg or 136K. Verify that there is a low Ohm reading from the tip to one of th...

A fender Bassman schematic calls for -48 volts. At -45 volts your output tubes will get getting very hot to the touch very fast, in fact in a darkened room you might see there plate structure glowing red and you do not want that taking place! its been on for at least 30 minutes and I can still touc...

maxkracht wrote: ↑Sat Jul 06, 2024 6:36 pm Negative bias voltage confirms the diode and the bias circuit are correct, filter caps not exploding confirms they are installed in the right orientation.

Thanks!

The -45 means you have bias voltage, that reading was with the rectifier in and power tubes out, so you don't fry the power tubes if the bias is wrong, but leaving the tubes in was fine. I think you have the 4, 8 ohm speakers wired correctly, in parallel, this should give you 2 ohms total. I would ...

LOUDthud wrote: ↑Sat Jul 06, 2024 7:14 pm Are those Voltage readings you took in the layout picture of post #1 ? Check connections around the middle preamp tube. Is pin 1 connected to pin 7 ?

Yes. And 7 and 1 are and they arw to 5

maxkracht wrote: ↑Sat Jul 06, 2024 6:36 pm Negative bias voltage confirms the diode and the bias circuit are correct, filter caps not exploding confirms they are installed in the right orientation.

Thank you!

What if I didn't have the filter caps in right? I followed the diagram. Would that cause a drop in volume across the board?

6.4 on the speakers so they are good. How about this (diode?) Is it wired right direction? Grey stripe to left.

Thanks guys for answering! I totally gutted and resoldered the leads. I am getting the exact same results as the first. I checked all but the power tubes in my Super so I know they are good. As for the pin 5, I have -45 dc with the tubes in. Steve, I'm a newb. Do I take that reading with all tubes i...

Hello all. I've read a BUNCH of similar problems, but I haven't been lucky enough to run into my answer. I've watched YouTube videos as well. This is my 3rd amp build, I have a Tweed Deluxe and Tweed Super I have already built. I'm no electrician. I vaguely get the schematics, so I rely on the wirin...