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Okay, so my new sIII sounds killer on the normal channel, but the TMB channel is full of white noise with intermittent crackling noises. It sounds like a radio that can't find a station. I have re-flowed all of the solder joints associated with the TMB channel, and replaced the 100k resistor on V2 (it was cracked), to no avail. I have checked other posts regarding this, and the only thing I have found that I didn't try is to replace the 500pF capacitor. Anyone have any suggestions that can take the crackle and static out of my amp?

Have you checked V1? I have had a 12AX7 where one side was stuffed before now.

I have smiler problem minus the cracklings, been trying few things but nothing worked so far. I will follow this thread closely. Good luck jimmy

I did not re-flow the joints on V1, but they all look shiny to me. I have swapped preamp tubes in all positions to no avail. I will take another look at V1 tomorrow.

Please measure to see if there is any DC voltage on the sIII control channel pots terminals. That can indicate a leaky cap.

Make sure the resistor on V2 is soldered in well and in good shape. I normally send a metal film for this purpose.

Check all ground connections on sIII channel.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Jimmy did you resolve this yet?

Haven't had the time. Perhaps this week. I will keep you posted.

Great hope you find a solution, in the mean time I will continue to search and see if I find one. If I do I will post it here.

Unlikely, but when you wiggle the tubes, goes the problem get worse/better/no change? Trying to eliminate the tube sockets here.

Not a bad idea to reflow the solder joints.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

So I finally had time to try and track this down. (I just wish I could find some time to practice, lol!) I tested for DC voltage on the TMB pots as requested above, and I found that a couple of the lugs on the MV pot as well as the Treble pot were reading some minor DC voltage. It was fluctuating between 1.5 and 2.5 volts, and it didn't seem to react to any change in the pot settings. Is this a significant indicator for a leaky cap, or is this small amount of voltage normal?

FWIW I have basically reflowed everything to do with the TMB channel, tested for continuity and resistance in all the grounds, and chopsticked 'til I was Chinese, and there is little to no improvement in the problem.

If I don't get this fixed soon, I'm gonna have to shell out for my amp tech to look it over. I know that isn't really in the spirit of the DIY experience, but I can't take this any more.

Book a flight. Stephen and I will take you out for a pint.

FWIW, I'm using your build log to guide me when I have questions.

Not normal. Should be practically Zero. If you measure on the control side of the 500 pf you get DC voltage? Then I would replace that 500 pf Silver Mica. I can send you one.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Just tested the control side of the cap, and I am indeed getting voltage. It's fluctuating between 1.5 and 2 volts, just like it was on the pot lugs. Could it be we've found the problem??? I sure hope so. I'll post again when I get it replaced and let you know!

Good chance that's the problem. Any 500pf cap can be used there but I'll send you a Silver Mica unless you can easily find one locally.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I've got to place an order with Mouser anyway. I'm going to perform some mods on my Tweed Deluxe clone (I've got the fever!!) so I'll just pick up a couple of spares while I'm at it. Thanks for the offer, though!

Just to update the situation as promised, I have replaced the suspect 500pf cap. And.......(drumroll please)........no more noise!! This was indeed the problem. There is still some noticeable hiss on the TMB channel, but from all i've heard this is to be expected. It's not annoyingly loud mind you, fine for playing live. However if I ever start recording with this amp, I may consider replacing some of the resistors with metal film as Stephen has recommended here many times.

My cabinet just arrived yesterday and it looks killer!! (Thanks, Stephen!) I will post pics when I get it all installed.

Awesome news!!

Hiss is normal for carbon comps and hard to hear on recordings BTW..

I will have to look into my vendor regarding the Silver Mica caps. I might change to .0005uf Metalized Polypropylene instead.

Next - Pics & Clips!!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps