Crack w/ Speedball intermittent crackling and fuzz [resolved]

[Paul Birkeland]

When the LEDs go out, those voltages will change.   Which LEDs would turn off?  Can you measure the voltages with the LEDs off?

[Nignoog]

The 12AU7 does not sit soundly in the socket. When the left channel cuts out, if I gentled rock or tilt the tube, I can get sound back. Could that be the tube, socket or joint?

[Nignoog]

The two LEDs that sit under the 12AU7 socket. I had previously jumped A3 to A8 (I think, can't remember), because one of the LEDs was out, but now if I rock the tube back and forth when the left channel cuts out, I can sometimes get both LEDs to light.

Would you like me to purposely move the socket into a positions where the sound cuts out on one or both channels and then test the voltage?

Thanks for your help by the way. You're being incredibly helpful and patient with me and I sincerely appreciate it.

[Paul Birkeland]

That is nearly always a loose connection on the socket or with something connected to the socket.

How is the solder joint on the center pin of the 9 pin socket?

[Nignoog]

I reflowed the center pin and firmly pushed down on the surrounding pins. I figured it couldn't hurt to see if maybe one or more weren't properly in place. Seems to have done the trick keeping the tube from popping in and out and distorting. However, the right channel is back to being noticeably louder than the left. Any ideas with that?

Edit: I believe the right/left channel imbalance was caused by my having the computer and spotify volume at max and the potentiometer turned only slightly up. By decreasing the volume on windows and turning up the potentiometer, the volume levels seem more even. However, the tube still randomly cuts the left channel out which I can fix by wiggling the tube. Back to square one in that regard. Should I try reflowing the center pin again?

[Paul Birkeland]

How are your voltages? Can you post them?

[Nignoog]

You got it. Here they are:

OA - 73
IA - 184
B-A/B - 0
IB - 183
OB - 71

OA - 107
OB - 110
G - 0
B+ - 184

These are nearly identical to the readings I submitted a few posts back. I did notice, however, that the bolded leads I measured produced static and fuzz when I touch the meter to them. On the small board OA affected the right channel and OB affected the left. On the large board I think OA affected both but that was less pronounced than the leads on the small board.

[Paul Birkeland]

Does the channel balance issue persist with the volume pot turned way up? 

[Nignoog]

With no way to test it other than my ears, I’d say it does not persist. Though the left channel cutting out and intermitent popping does persist unfortunately. What are your thoughts on the voltages?

[Paul Birkeland]

Your voltages look OK.  Some channel imbalance at very low volume levels can be a function of the stock volume pot, but the popping and cutouts you describe are symptomatic of a loose or poorly soldered connection that is still giving you some problems.

[adydula]

IF you wiggle the 12AU7 tube and see the leds go on and off....I will bet you one or both are not soldered well and/or the leds themselves might have a fractured lead and will
need to be replaced even if they light up intermittently...

I had this issue and it was when I was taking in and out tubes searching for audio nirvana and realized when these leds are soldered in with no sttrain relief they will "make and break" over time..

Sometimes work for weeks and then voila pop and no light, wiggle get the led back on until the issue reappers.

I replaced the leds on the 12AU7 and bent the leads to allow for some movement...even then you have to be careful removing and inserting tubes..

Good Luck
Alex

[Nignoog]

Thank you both for your responses. Certainly makes sense. This problem started after I removed the tube for the first time. So it’s possible I loosened or broke an otherwise good connection. I’ll do some investigating this evening and try to clean or reflow some joints.

[Nignoog]

After a lot of reflowing and chopsticking every joing on the 9 pin, I have fixed most of the problems. I will continue using it to see if any problems resurface. The only issue now is there is a very quite high pitch ringing, almost like a harmonic, in the right channel. It's very quite and will occasionally fade in and out. Any thoughts on that? I can only assume it has to still be centered around the 9 pin socket.

And thank you to everyone who helped me get this far. It feels so good to have made progress!

[Paul Birkeland]

That could be related to your phone's cellular broadcast or some other nearby appliance.

[Nignoog]

The static/fuzz keeps resurfacing. I have two observations as I been trying to pinpoint what the exact problem is.

1. Using a thin wooden skewer, I poked and prodded until the crackling and distortion stopped. I left the amp running all night and found that when I listened to it, it still sounded great; no issues. But when I turned it off and let it rest for a few hours and then turned it on again, the issues arose again. Does temperature (heating up, staying hot, cooling off) play an issue? If so, does it reveal anything meaningful in terms of troubleshooting?

2. When I first built the crack, my voltages were off and one LED wouldn't light up. Through the help of the forum, I soldered a wire between A3 and A8 and the problem was alleviated. Now, if I poke the socket in the right way, I can sometimes get both LEDs to light up. Additionally, it appears as though A3 and A8 and maybe the center pin with the LEDs is the primary culprit for the left channel dropping out and the static/fuzz to occur. I am wondering if this means those joints need to be reflowed or if maybe the wire between 3 and 8 should be removed.

Fingers crossed we can finally resolve this soon! Thanks.