Crack w/ Speedball intermittent crackling and fuzz [resolved]

[Nignoog]

I completed my crack with speedball upgrade a few weeks ago. It ran flawlessly until a few days ago. There are sporadic instances where there will be popping or crackling in both channels. I can usually fix it by firmly tapping the chassis on the right side of the vent (between the tubes, just above the headphone output). Interestingly, it appears as though the tapping is somewhat audible, or being picked up, in my headphones. After a few taps, the crackling goes away for a while only to randomly return.

I tried tightening all screws on the topside of the chassis that hold the tubes. I imagine the next step would be to do the chopstick test unless someone can recommend a better solution based on my description. Thanks for reading.

[Doc B.]

Reflow the solder joints around the area where you can create the popping noise by tapping.

[Nignoog]

Will do and will report back. Thank you Doc.

[Nignoog]

Reporting back. Issues are worse now. Here is what happened.

I reflowed around the 6080 tube socket because this is where the problem would be temporarily alleviated if I tapped around it. And it seems to have fixed the crackling/fuzz issue. However, there was a very faint, high pitch tone in the right channel. On the forum, it appeared many solutions involved removing tube and in some cases cleaning the tube pins. I removed the tubes, hit them with compressed air to blow anything off, gave them a quick rub with isopropyl alcohol on q-tips and plugged them back in. The tubes seem to light up just fine, though the 12AU7 seems to be fainter than I remember, but now there is NO sound at all. Once the amp properly warms up there is a very low, deep hum in both channels. I checked the voltage on my speedball and notice that the OA and OB voltages are in the 180s!!! The OA and OB voltages on the large PCB are also in the 180s. All LEDs light up though.

I am so bummed! I find it highly suspect that removing the tubes, applying a little cleaning and reinserting them would lead to such an anomaly. But I am an amateur, so what do I know? I wonder if one of the tubes is broken because I had to pull and wiggle them quite hard to get them out. Any diagnostic help would be greatly appreciated. Thanks.

[Paul Birkeland]

Voltages in the 180s on the OA and OB terminals on the small PC board means that the 12AU7 isn't conducting.  This is nearly always from a bad solder joint, and would never be from anything having to do with the 6080 tube itself, unless the guide pin is broken and the tube got inserted into the socket improperly.

[Nignoog]

Thank you for the prompt reply. Any guidance on where to start? Or should I remove the small PCB and reflow the joints on every 12AU7 pin?

Additionally, based on my description, why would the 12AU7 have conducted properly but now will not conduct? Is it possible that removing and reinserting the tube jostled or revealed a faulty joint?

And lastly, would limited or non-conductivity result in my perception that the tube is glowing less luminously?

Thanks again for your time and help! Though it is frustrating, I appreciate being able to learn along the way. I will report back when I return from work this evening.

[Paul Birkeland]

Thank you for the prompt reply. Any guidance on where to start? Or should I remove the small PCB and reflow the joints on every 12AU7 pin?

Perhaps posting some photos instead will narrow things down a little bit.

Additionally, based on my description, why would the 12AU7 have conducted properly but now will not conduct? Is it possible that removing and reinserting the tube jostled or revealed a faulty joint?

Yes, every time you move the amp or insert/remove a tube, a faulty connection may respond.

And lastly, would limited or non-conductivity result in my perception that the tube is glowing less luminously?

This is potentially true.  Sometimes a bad solder joint on B7 or B8 will solder the wires fine that heat the 6080, but be a little loose on the wires that run up to the 9 pin socket.

[Nignoog]

After many grueling hours of troubleshooting and reflowing, I have eliminated the popping and crackling when I tap the chassis. But, I now have a light hiss in the right channel. The hiss is constant and there are waves of minor crescendos. I reflowed every joint I could access, most notably the headphone socket joints and 12AU7 socket joints, but cannot seem to get rid of the hissing.

I believe a possible culprit is not the solder joints, though they were certainly part of it, but rather the 12AU7 tube and/or socket. The tube won't sit in the socket comfortably. When I lift the chassis and the LEDs aren't glowing, all I need to do is push the tube one way or another to get things to work properly. I removed the tube and tried tightening the screws but to no avail. One interesting thing to note, if no LEDs light up, I get no sound. If I get one LED to light up I get sound, and if I adjust the tube and get both LEDs on, the sound doesn't seem to be affected at all.

Is there any solution besides reflowing joints to solve hissing in the right channel? I spent so long reflowing joints but I kept causing other issues I then had to solve. Thanks for your help!

[Nignoog]

Well, we can mark this as solved... for now. I searched forum for "crack right channel hiss" and found this:

https://bottlehead.com/smf/index.php?topic=10476.msg96167#msg96167

I tightened my speedball screws and it's dead silent now. I will continue to use it and will report back if any issues arise. I am so relieved! Thanks for all your help, this is truly a fantastic community.

[Nignoog]

What a rollercoaster. After a few hours of great listening, a warm crackling sound occurred in my right channel, followed by loud popping. Then both channels significantly decreased in volume and there was heavy fuzz in the right channel. The left channel is dead too. Any ideas?

Edit: It seems the two screw holding the small PCB can cause or cure the popping and crackling. Is there something on related on that I should investigate? I am also noticing that when I don't plug the headphones all the way in, I get the left channel to come in. And whatever sound the right channel produces, the left channel mirrors. So if the right channel is clear and smooth, so is the left. And when the right channel is distorted, the left one is too.

Edit 2: In frustration, I decided to poke and prod with a chopstick. Lo and behold, I discovered the R1A joint was loose. When I poked it, it caused static. I gave it a bit of solder and BEFORE I screwed the PCBs back in I tested it. Perfect. Then I screwed the PCBs back in and the left channel was missing again. My hand brushed against my headphone cable and the left channeled popped and then came in cleanly. I am going to call it a night and run it tomorrow and see if it holds. If you're still reading my saga, thank you. I can't wait to have this solved!

[Nignoog]

Listened for a few hours this morning. Everything was fine. No crackling, popping or distortion. But then the left channel stopped working entirely again. Poking, prodding and tapping yield no results. Should I go back to reflowing joints again?

Edit: Turned it off and went back to browsing the forum for ideas. Said a little prayer, turned it back on and both channels are working again. I am going to let it run and see if the left channel cuts out again. This is so weird!

[Paul Birkeland]

When the channel dies, the voltages will change.  Letting us know what your voltages are will help us determine what to do next.

The screws that hold the Speedball boards to their standoffs are not that critical in terms of torque, but the screws holding the TIP50 transistors on should be pretty tight.

[Nignoog]

If the left channel goes out I will note the voltages and post them. Now that the sound is back on, the right channel is ~20% louder than the left. Any way to fix that?

[Paul Birkeland]

Again, measure your voltages and report them to us.

If your voltages do not follow the guidelines in the manual, your amp is not safe for use.

[Nignoog]

Here are my voltages. When the left channel cut out, the voltages remained the same. When I tipped the board up to measure the voltages, there was a certain angle that would cause all sound to cut out. The LEDs shut off too. But once I tilted it more vertically or placed it back in position, it functioned fine. The channel imbalance where the right is louder than the left is still present when the left channel does work.

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

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