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Post subject: Re: Twin Reverb '65 Reissue
Posted: Thu Jun 15, 2017 9:19 pm
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Location: Coastal Bend, Tx.
Have you checked the PSU capacitance ranges, still w/in tolerance not leaking. Just a WAG on my part. But w/ a blown fuse, you never know.


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Post subject: Re: Twin Reverb '65 Reissue
Posted: Thu Jun 15, 2017 10:26 pm
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7chord wrote:
Sure did, and they are fine; well at least from the top side of the board.


When you pull the board, check the traces there on the reverse side very thoroughly.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Twin Reverb '65 Reissue
Posted: Fri Jun 16, 2017 7:33 pm
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You how when you've been staring at a problem long enough you stop thinking logically about it even though you *think* you're being logical? Sometimes you just think you've done what you haven't done, or vice versa.

Being a creature of habit, I always install the BiasMaster sockets in the same order so that I always know v7 is position 1 on the switch, v8 is 2, etc. After cleaning and tightening the OT sockets, I decided to just install two BiasMaster plugs, which went into positions v7 & v8. I also reversed the order of the tubes, though not intentionally. I powered the amp on and immediately felt like a complete idiot. OT v8 was now showing nearly 70ma.

I obviously had not done what I thought I had done. Stupid.

I switched the BiasMaster plugs to v9 & v10 and those tubes happily idled at 35ma. Swapped the tube pairs between v7 & v8 and v9 & v10 and the problem does indeed follow the tubes. How I missed that, I have no idea.

It appears that at least one of the tubes in the quad is bad (or seriously mismatched??); it reliably shows almost twice the plate current of the other 3 OT's, no matter which socket it's installed in. I don't know if they were purchased as a matched quad or not; investigation to follow.

But, that's why I couldn't find any other problem in the amp. The problem was me. :oops:


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Post subject: Re: Twin Reverb '65 Reissue
Posted: Fri Jun 16, 2017 11:03 pm
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7chord wrote:
The problem was me. :oops:


Don't beat yourself up. We've all "been there, done that, got the T-shirt". That you persevered and finally solved the issue is to your credit.

Rawk on!

8)

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Twin Reverb '65 Reissue
Posted: Sat Jun 17, 2017 7:17 am
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Nothing like shooting yourself in the foot, then limping around it the long way... :lol:


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Post subject: Re: Twin Reverb '65 Reissue
Posted: Sat Jun 17, 2017 9:52 am
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7chord wrote:
Nothing like shooting yourself in the foot, then limping around it the long way... :lol:


It beats laying on a coroner's stainless-steel examination table, wearing a toe tag......

:mrgreen:

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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