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Post subject: 65' TRRI cap questions
Posted: Mon Sep 27, 2010 5:10 pm
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I have a 98' TRRI with illinois caps and have a few questions.
1.
I will be replacing filter caps on my twin with f&t's and was wondering what other caps I should replace since i'm gonna be in there. Any suggestions?
2.
Are the bias caps the C35 100uf/100v and the C36 22uf/63v? If so, any other value I can use for the 22uf/63v. I'm having trouble locating this one at 63v? Would a 25uf/50v suffice?
3.
For a couple of buck more I can get the sprague atoms, but are they really worth it? I've heard pretty good things about the f&t's.

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Posted: Mon Sep 27, 2010 10:59 pm
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The voltage rating can go up to 100VDC on that bias cap. Test any caps prior to installation. Just a suggestion. Art

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Posted: Tue Sep 28, 2010 1:17 pm
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Yep, good capacitors are well worth the money.

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Posted: Tue Sep 28, 2010 6:27 pm
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Art and Supro,
Thanks for your input.

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Posted: Sat Oct 02, 2010 6:40 pm
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Wel I completed my filter cap replacement project today. I installed sprague atoms 20uf/500v X3 and F&T 220uf/300v X2. The results, Wow. Very much worth the hassle of trying to figure out how to squeeze those enormous spagues where the tiny Illinois caps used to be, but I improvised :wink: .
The bass is tight and very pronounced. I used to have to turn the bass to between 6 and 8 to get the bottom end going and now anywhere between 4 and 6 will do. Also noticed that before the cap job I really had to turn the treble down because it sounded very annoying, not anymore. Seems like the cap job smoothed out the treble. Are these sound improvements typical of a filter cap job?
I also went ahead and ordered the coupling capacitors as well as the tone caps for the vibrato channel, as thats the one I use the most. I'm looking forward to seeing what improvements, if any those new caps will provide. I got orange drop for the tone caps and Mallory for the coupling caps. That will be my next upgrade. But while I was in there, I noticed that I might have to find a way to squeeze those massive orange drops to replace the existing ones :lol: . Is it worth the trouble?

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Posted: Sat Oct 02, 2010 7:57 pm
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Hey 323, glad to hear you found a sonic improvement, for all your work ! Just wondering if you ended up stacking the Spragues ? If so, then a little bit of silicone between the caps might be a good idea. Vibration can cause a cap to go microphonic. Yeah, you can usually hear the difference with a filter recap, the amp should be getting a cleaner power supply. As for the other caps, it's a hard call. Of course the reliability will be inhanced, but the sonic benefit may be subtle. I use a lot of high zoot caps in my two BF amps. IMO The sonic pay-off is only in the recording realm, in a live band mix, they just don't get to shine. That being said, I've had good results using the OD caps and silver mica in the tone stacks, and you can't go wrong with the Mallorys, for coupling. Is it worth the effort ? Your amp is kind of tough to work on, but I'd go with your gut feeling on those caps. Art

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Posted: Sun Oct 03, 2010 8:24 am
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Art,
I didnt stack the caps but I did use a hot glue gun to keep all the caps in place. I used it underneath and between the caps that are located in the "pan". Is it necessary to apply it to the one mounted on the pcb? This one sits all by its lonesome, far far away from all the other filter caps.

As for the other caps, maybe next time i've got the amp apart I'll replace the OD's and the Mallorys. I'm pretty used to taking things apart and working in hard places, it's kind of what I do for a living. I'm a service tech for a large Wide Format company. :lol:

For now, I think I'm gonna order a new set of power tubes with a PI that has balanced triodes. Is it a good idea to also order a 12ax7 with balanced triodes for the 1st gain stage? In my case it would be v2 since I use that channel the most, and what about v4? I've heard it's worth it.
Thanks for your response.
Abe.

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Posted: Sun Oct 03, 2010 8:39 am
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Balanced transconductance between the halves of a twin triode where these halves are cascaded as gain stages is really not critical to amp performance. It won't hurt of course but it's likely an unnecessary expense. Better to put that $$$ into finding a primo quartet of matched output bottles. The V6 12AT7 requires equilibrium between the elements to optimize the duty cycle of the output stage and prevent premature power tube failure.

HTH

Arjay

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Posted: Sun Oct 03, 2010 8:48 am
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So put the money into quality power tubes and PI, got it.
Thanks Arjay,
Abe.

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Posted: Sun Oct 03, 2010 7:26 pm
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Yeah Abe, Arjay's spot-on. No need to mess with the cap on the board, unless it's floppin' around in the wind. To be honest ,I haven't seen a TRRI for many years(probably the year after they came out), and that was not for repairs. For some reason, I was thinking they put those caps inside the chassis. But the cap pan is actually superior, for shielding and cooling purposes. Good decision on the other caps. In the meantime, Keep Pickin' ! Art

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