Reoccurring Static [solved]

[squirreldude]

Hello all,

I had an issue a while back ( http://bottlehead.com/smf/index.php?topic=5350 ) with an intermittent scratching/static sound in both channels. I sent the amp in for repair and Paul did great work cleaning it up, but the static has slowly returned over the past couple months. From what I've read, it fits the description of a cold joint, but I doubt that the amp would come out of BH repair with a cold joint. However unlikely, I still invested in good soldering station and reheated everything myself with no success. I get static in every sitting with multiple combinations of power and input tubes.

I'm really at a loss for how to solve this or what to do with the amp. I thought that sending it for professional repair would be the final solution, and I don't know how to proceed at this point. Any thoughts or advice about what else may be wrong?

Thanks,
Karl

[Paul Birkeland]

Can you describe the nature of how the static returned?  Is it in both channels?  Does it happen regardless of the source component used? 

There are occasions where noises like these are environmentally related, with certain appliances, light dimmers, and electronics producing interference at random intervals.

Regardless, we will warranty the repair if you believe the amp is still acting up, but it would be good to narrow down any potential sources of noise that might be in your residence.

(One way to narrow this down is to take your Crack to work and run it there for a few weeks, just to verify that the same issue occurs)

-PB

[squirreldude]

When the amp came back from service, I only heard the static sound ~once a month. It wasn't reliably reproducible then, but the static picked up in frequency as time went on. It evolved from a monthly event to a weekly problem and now it happens on a daily basis. It's in both channels and happens regardless of any source being plugged in. It's also volume independent.

I don't think it's an environmental issue either. I just moved a couple weeks ago and it seems to have no impact on the static. I tried plugging it in in various rooms of both houses, but I will go traveling with the amp just to be sure.

I can make some ignorant guesses about what might be to blame, if it helps...
1. Maybe I damaged some component(s) while building the amp
2. My power supply had an unusual problem with 1 wire being disconnected from the metal terminal strip. Paul, you fixed this during the repair.
3. My soldering skills are so poor that the amp is beyond repair
4. The top plate is curved upward slightly and flexes when I swap tubes, plug in headphones, or adjust volume. Could this break a solder joint?

[Paul Birkeland]

If you still have the box, you could send it back and I'll have another look.

The one thing that immediately comes to mind is that the #8 screw by the power entry module and the #4 screw on the rear side of the 9 pin socket should be tight for the amp to work properly, and they may loosen over time (and shipping).  Also, the transformer screws should be pretty snug.

Beyond snugging those screws up, I'd be happy to take another look at your amp to suss out this static.  If I remember correctly, the loose wire in your power supply had damaged a component or two, but it's certainly possible that I missed one!

-PB

[squirreldude]

Last week, I twisted all the screws visible from the top. None of them were particularly loose, but it seems to have eliminated the issue. I marked the thread as solved and I'll keep an ear open for the next few weeks. Thanks, Paul.