Tube Amp Archive

Hopefully this is a good section for this thread. I know typically it's all amp-related but it's at least about a speaker... I've got a Yamaha S115V PA speaker. 15" Speaker and a Horn up top. No sound out of the speaker, just the horn. I pull the speaker and see that the bi-polar electrolytic is des...

Even though I'm not doing the "full" conversion are you still interested in hearing both before and after? I haven't been able to properly bias the tubes since changing it to a standard bias system...I've got it turned as "cold" as it'll go and my GOD does it ever sound good! :o Strangely, my plywoo...

Decided not to go to all the trouble. Changed it to a standard fixed bias system last night. Gonna do a "1/2" BF and call it good.

Alright, I've got the schematic. I think what i was looking at is a resistor value over on what looks like pin 4. the "other" side of the STBY switch states 520v, so I guess that's correct.

In the house? If that is what you're asking it's 123 vac (or is that acv)

This UltraLinear '79 or so Pro Reverb I've been working on - I changed it to a "standard" bias system today. While I was in there I decided to see what kind of high voltage was REALLY coming from the power supply. 517 volts at the plate!!! The spec on the schematic shows voltage here should be 470 v...

Hopefully this gets read: Following this how-to http://www.el34world.com/charts/bias_conversions.htm I understand how it works and what to do...however in all of the examples he uses the amps all have a 100k resistor in the original spot. My Pro has a 47k there. Am I still okay to change it and add ...

Maybe that's my cue to attempt some recordings.

What would someone want to hear? Low vol, high vol, gain, no gain...

I think that what we're looking at doing requires the taps to be moved because he said there's a chance of the coil taps arcing because of the power we plan to pull. Raising voltage somewhere. I do have the volume dimed when I use it. We had a long gig last night and I had the MV at 10 and the chann...

Taking out the taps and moving the plate voltage to B+ rather than the taps. Moving a few wires, removing a few thing like the MV and it's associated crap... The plates are already tied to B+1; the question is, where are you going to connect the screens? You'll need an additional node in the power ...

---Can't you just tie back the UL taps and then reboard it with BF stuff? Extensive, but not expensive.---- Yes. That's what we're doing. Taking out the taps and moving the plate voltage to B+ rather than the taps. Moving a few wires, removing a few thing like the MV and it's associated crap... I do...

Hey everyone, been nosing around the forum for a few days and thought I'd come join in. I got a 78-79 or so UL Pro Reverb from a friend of mine and decided I wanted to BF mod it. I didn't know at first that you can't really do that to the UL's, and then got in touch with an amp tech who will help me...