Static / Pops in Left Ear

[remedy]

When I initially assembled my Crack (no speedball) I was completely new to soldering and made lots of solder blobs, scorched some insulation, and melted some of the heatshrink on 1 capacitor.

Fortunately, it worked! Resistance checks were good, and voltage checks were solid. But I had a low hum that played constantly which was very irritating. It got louder if I turned the volume up and was still there if I unplugged the source. I resolved to reflow all my joints. After that, the hum was gone. The amp was dead silent and worked flawlessly.

And here's where I went wrong. I decided it'd be a good idea to fix all of the novice errors I made in the initial assembly. I  replaced the cap that I melted the film of with an identical one and replaced the wires that I had scorched. I also switched the ground wire from the power transformer terminal 4 to terminal 14 instead of terminal 22L which I had it wired to originally.

Unfortunately, now I have static in the left ear. There are occasional pops, which don't change with volume nor do they go away with the source unplugged. Resistance and voltages are still fine, and I've reflowed every solder joint with solder wick to remove the blobs and done it all over again multiple times. I also tried the chopstick test and was able to produce a little crackle when poking around pin A7, but reflowing that seemed to resolve that. After that the chopstick test yielded no results, everything was dead quiet but that static was still present.

I've reinserted both tubes at least 10 times to clean the pins as I read Grainger recommended to another customer who had issues, no luck there either.

I don't really have spare tubes, but I had an 12BH7 from another gadget that I popped in to see if it resolved anything to no avail. The only thing I haven't done is swap out the power tube.

One last thing about that background hum, it came back during one of my many resoldering phases, but was resolved by lightly rapping on the power transformer.

For the life of me I cannot figure out how to get rid of this left side static. It's driving me crazy and I wish I had just left the amp alone after fixing the hum instead of trying to perfect everything.

I can't post any pictures until I get my phone back tomorrow (screens just love to shatter!), but I will if that would be helpful when I can do so.

Thanks in advance for any help.

[Nathan]

Cold solder joint somewhere

What kind of solder and soldering iron/station are you using?

[remedy]

I'm using Alpha-Fry 60/40 Rosin Core Solder and a Weller 40W Soldering Station.

I've looked at the joints with a magnifying glass, but I don't exactly know what a cold joint would look like versus a good one.

One other thing I did notice is that if I plug in my headphones and rotate the connector while its plugged in that I'll get some noise in the left side, not sure if that's normal or not or even relevant but thought I'd mention it.

[Doc B.]

Yes, that is the reason we suggest simply reheating and reflowing all of them. You really can't be certain a solder joint is good just by looking at it, because you can't see inside where there might be flux or some crud interfereing with the continuity.

[remedy]

Got it. Would I be better suited to removing the solder that's on the joints and just resoldering everything? Or should I just reheat them as you said to allow the solder that's there to flow?

Thank you so much for putting up with my novice questions, and I really appreciate the help.

[Doc B.]

We suggest simply reheating and reflowing all of them.

[remedy]

Spent about an hour and a half reflowing all the joints, no luck. The static is really strange, it's much louder when I first turn the amp on and comes and goes along with pops. It becomes much quieter after about 5 minutes but is still happening. It's inaudible when listening to anything, but quite irritating when nothing is playing. After the amp settles in and the left side static quiets down, I start getting static in the right ear now too. There's no static in the right ear until after the amp settles in.

Frustrating!


Forgot to mention, one of the 100uf 160v caps has a bit of the heatshrink melted too. But that has been like that since I first assembled the amp and it was working well without noise.

I did buy a speedball kit and have it assembled, so I was thinking I would put it in to see if it fixed my issues as it bypasses some components, but one of the leds of a 22.1k 3/4w resistor broke off. Can't seem to find anywhere to buy one of those on the internet either, so there goes that option.

[Doc B.]

About the only things left that could make that sound would be tubes or damaged caps. If a film cap gets a nick rom a soldering iron that can create the problem.

[2wo]

Did you plug the tubes in 10 or so times?
  Or sometimes a tube will be a bit crackly for a while, give them 50 hours, often they settle down...John   

[remedy]

About the only things left that could make that sound would be tubes or damaged caps. If a film cap gets a nick rom a soldering iron that can create the problem.

new the 100 uf new caps got in today, replaced them both. No luck. I'll try replacing both tubes now I suppose.

John: Yes I did try that, that was in my original post.

[remedy]

Ordered some new tubes. How would I go about getting another 22.1k resistor for the speedball as the lead broke off mine?

[remedy]

Crack is now silent after cleaning joints with a toothbrush and rubbing alcohol, cleaning the chassis with steel wool, and reflowing the 3 power capacitors. So you were right that it was indeed a cold solder joint!

So all that remains is how would I get a new set of 22.1k resistors for the speedball?

[Paul Birkeland]

The 22.1K resistors on the Speedball board can be replaced by a single 47K 1W or 47K 2W resistor, which may be very easy to find locally (to avoid shipping costs).