Twin Reverb.. last issue.

[g1]

We'll wait here.

[Sea Chief]

We'll wait here.

No joy with adding the cap. Exactly the same. I tried moving a few wires, but no change either- so I'm finally defeated.

Thanks anyway: at least the POP's & reverb noise has been fixed.

It's now send the bloody thing off to amp repairer. An utter beast to post/ what I was hoping not to do.

If that doesn't fix it.. Im throwing the fkn thing in the river. Im SO sick of tube amps!

SC

[Sea Chief]

Hi chaps.

Though I'd update you. I sent amp off to a colleague/ builder, who located the trem issue & resolved it. The v4 socket needed replacing, v4 tube slightly microphonic, plus one wire redone he said. So trem sounds good! Such a hugely problematic amp just to pack for post, this was my very last resort.

--- but ---

Although my 3 main problems solved ( POPs/ crunchy noises, reverb hum, & the ticky trem) & all sounded good with amp on bench just back from posting (no post damage afaict) connected up to cabinet still facing wall.. once amp back together & in my living room finally at last (!) it seems I have, unfortunately, a generally intrusively loud "groundy hum" behind the sound of the guitar. You can play away ok, but it is Irritatingly prominent.

So I have one last hurdle to jump. My builder didn't register it he says when amp with him, so this is confusing.

Could anyone help?

Thanks, SC

[pdf64]

Your amp was originally fitted with ‘output tube matching’ and ‘hum balance’ controls on its rear panel. Both of these may affect ‘groundy hum’.
Assuming they’re still fitted and have their original functionality, have you tried tweaking them?

[Sea Chief]

Your amp was originally fitted with ‘output tube matching’ and ‘hum balance’ controls on its rear panel. Both of these may affect ‘groundy hum’.
Assuming they’re still fitted and have their original functionality, have you tried tweaking them?

Hi pdf, good idea but actually these were made redundent. Well, assuming the matching whatnot was a bias control, this replaced with a typical ab763 internal bias pot/ circuit.

Thanks though, SC

[Sea Chief]

Your amp was originally fitted with ‘output tube matching’ and ‘hum balance’ controls on its rear panel. Both of these may affect ‘groundy hum’.
Assuming they’re still fitted and have their original functionality, have you tried tweaking them?

If one of my tubes is out of kilter to the other 3, bias-wise I mean, could this introduce prominent background hum?

I recall I sent Rift the amp & new tubes/ a matched JJ quad innitially way back, & when checking amp later once Id rebuilt it, I was surprised one tube was out of kilter like say 17 mA when the others all showed 24 mA (or something in this ballpark for both figures as I recall).. Rift said ' meh.. don't worry about it/ not critical'.

(I cant remember though the same bad hum once all checked out & amp "reborn".. which suggests I should look elesewhere maybe instead.)

Thanks SC

[nosaj]

Well if your ampguy didn't catch the tubes out of kilter I'd suspect him. Why don't you ask him if he checked them?
nosaj

[pdf64]

If one of my tubes is out of kilter to the other 3, bias-wise I mean, could this introduce prominent background hum? …

Yes, hence my enquiry regarding the ‘output tube matching’ control, as that’s what it affects / corrects for (or exacerbates if wrongly adjusted).
I agree that 5mA is a negligible discrepancy, but things could be worse after being bounced around in the journey back and forth.

[Sea Chief]

Well if your ampguy didn't catch the tubes out of kilter I'd suspect him. Why don't you ask him if he checked them?
nosaj

Hi there nosaj. Well he did the tremolo fix work, including a new socket & tube, & even posted it back to me ( beastly heavy).. all totally free for me. A huge favour.

So I couldn't possibly ask him if he checked them, he may well not have (it wasn't at his for a full service only this tremolo issue needed addressing).

In fact I did mentioned it to him & said " no probs at all- my great chaps online might help one last time" & he did reply apologising & that he didn't notice it. Kindest chap.

So regardless of how it occured, I just would like to try ( one final-final hurdle ! ) possibly with your fine help on here, to trace & sort it.

(Btw he complimented me on my build work! So there all you naysayers..:-). Thanks SC

[Sea Chief]

Yes, hence my enquiry regarding the ‘output tube matching’ control, as that’s what it affects / corrects for (or exacerbates if wrongly adjusted).
I agree that 5mA is a negligible discrepancy, but things could be worse after being bounced around in the journey back and forth.

Aha ok pdf. Well as well as we packed the beast, & no box knocks/ bashes afaict, it might have been launched around a van a bit.

So would it make sense then to see what each tube bias reading is -currently- (another of my fabulous puns) after transit ?

Thanks SC

[pdf64]

Yes, if you can do it easily and safely, try that, see if it reveals anything.