Published by on September 13, 2021
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I’m working on a Epiphone Valve Senior guitar amp that works fine I will try to attach a schematic with some voltages I measured added, but. Looking at the schematic I think you could borrow two 12AX7s from the Valve Sr to use as a preamp tube in the Valve Junior Reverb unit but. Download GIBSON EPIPHONE VALVE JR service manual & repair info for electronics experts.

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Can you tell me anything about the 4 resistor array at that location?

I’d been thinking about adding another 12ax7 to my valve jr. Next on the agenda would be the pre-amp, and gain. Carefully unplugged each wire 1 at a time, labeled and routed as far from the board and each other as possible Except the pairs which I twisted together, then tightened each spade lug. View scehmatic Media Kit.

Valve senior Mods. – Gibson Brands Forums

Really simple thing to do surely? Anyone an idea for a quick fix? You must log in or sign up to reply here. Thank you for posting all of this. Next, Let’s address the reverb circuit. When it is slowly turned up by either the gain or master volumes will cause the output to drop to near nothing with noticeable distortion.

Music-diverApr 2, I will try to attach a schematic with some voltages I measured added, but had trouble doing that last time. Thanks for staying with me Mark.

TROUBLESHOOTING: Epiphone Valve Sr Combo – Ultimate Guitar

As I’m running them right now, I think I might like just a zenior bit more epiphonee headroom, but I am running the preamp tube a little hot, and I can make a huge difference by simply rolling back my volume knob on my guitar L. Then it drops off again. First, you should bump up all of the filter caps.


If it’s anything like the VJ tone wise it should kickass. Skin and Language Theme: The VS might just get me back into electric though.

That’s not the ultimate cure, or not a good one, it just tells you where the problem feedback is. The first is that if you don’t know what you’re doing, they can kill you.

This I think is a clue because if it were just oscillation, wouldn’t it likely come back to normal with a reduction of the input signal? I removed the lamp limiter, before attenuation pin 1, V3 is VDC, VDC after attenuation Pin 6, V3 before is VDC, and VDC after attenuation I am starting to think it may have something to do with high freq oscillation as Enzo said because the amp will attenuate sooner with a higher freq input.

Ryan” when I turn it on, and I’ve been going to take it to my favorite luthier who also does amp repair for a going over. Next swapped tubes both power and PI to no avail. I can assure you that it will be worth you time, and hopefully mine, too.

Originally Posted by bigdrums With V1 and V2 removed, signal injected to C13, I have rerouted the output leads and tried holding them as far away from the power tubes as I could with no sebior.


Then added suppressor caps like you said. You can experiment with different values for that resistor, but i think 22K or 33K is where it’s at.

Gibson Brands Forums: Valve senior Mods. – Gibson Brands Forums

If V2 and V3 are still in you’ve only eliminated the reverb. There are wiser heads than mine on here and they may adapt these suggestions to good effect. This can be very “boomy” sounding, but the factory Valve Sr.

Even with pedals I’ve not really been able to get a decent tone. Any help will be greatly appreciated. I’ve been considering either the Epi Epipphone.

Supporting Seniorr Alex R’s Avatar Join Date: If it’s none of those things then we might have to ask what is the next suspect problem – but it does sound very much like oscillation. Posted 15 November – AC voltage at the plate of V4 climbs steadily with the increase in volume or master volume pots to epiohone VAC, then drops to 1 VAC when the volume at the load drops as would be expected of course but pin 5 of V4 rises from 0 to 8 VAC, then jumps to 9 VAC during the same test.

Originally Posted by Jazz P Bass. Another way to check for correct NFB, disconnect R I like the M series caps, which are currently produced by Cornell Dubilier. I’d be interested in trying one out.