Very low consistent buzz, intermittent "popping" sound in headphones [resolved]

[Mike1590]

Hi all,

So I finished up my first Crack build yesterday. The amp passed all of the resistance/voltage tests. It worked great yesterday for a multiple hour listen. However, I turned it on today and noticed a very faint, consistent buzzing sound that I didn't notice the day before. Along with the buzz, there is an intermittent popping sound in the headphones - this certainly wasn't present yesterday.

So I have been searching the forums off and on today and found a variety of troubleshooting methods. Ultimately, none of these solved the issue, so I wanted to turn to the forums for some additional help. Below are all of the various troubleshooting methods I've tried. I have also posted a variety of photos of different solder joints along the interior of the chassis.

Test results from today, after re-soldering a couple of joints that I thought may have been problematic first:

Resistance

1 *
2 *
3 0
4 *
5 *

6 0
7 2.96 kO
8 0
9 2.95 kO
10 0

12 0
13 *
14 0
20 0
22 0

B3 2.96 kO
B6 2.95 kO

RCA Center Point RED 99.2 kO
RCA Center Point BLACK 90.3 kO
Both ground tabs 0

Voltage
1 81.9 V
2 165.3 V
3 0.8 mV
4 165.3 V
5 80.2 V
6 0.7 mV
7 104.1 V
8 1.0 mV
9 104.3 V
10 0.2 mV

When power was connected and the unit is turned on, both LEDs light up. I also noticed a slight shock earlier this morning, I think around the headphone jack on the chassis, so I found another thread on here where Doc explained how to test the chassis for any voltage by connecting the black terminal of the DMM to ground on the IEC and the red test lead to the chassis panel (when power is on). I did this, but the chassis measured 0 V in multiple tested locations. Earlier there was definitely some crackling/popping when I would wiggle/flick the 12AU7 tube, but I believe this was because the tube was not fully inserted into the 9 pin socket. Note, the occasional popping that I'm getting through my headphones is happening when I'm not fiddling around with this tube. However, I'm still not sure if there's a bad soldering joint somewhere on this 9 pin socket that could be the culprit.

Hopefully all of this helps. I will note that I am an extremely novice solderer (only soldered once before embarking on this project), so it's certainly very possible I have a bad joint somewhere.

Thanks in advance!

[Mike1590]

More photos, since my size limit was reached in the OP.

[Mike1590]

Since making this post I've reflowed/resoldered the majority of my joints and *knock on wood* the popping and buzzing are gone and the amp is completely silent now. I'd still appreciate any troubleshooting advice in case this issue crops back up again, but for the time being at least, it seems to have subsided.

[Paul Birkeland]

You have/had an unsoldered black wire on your headphone jack.

[Mike1590]

Thanks Paul. That’s what I figured, having seen that specifically mentioned in several other threads about this same subject. That’s where I started last night and I added a bit more solder to some of the joints on there. Still was working well when I tried everything out this AM.