New Popping in Crack [resolved]

[squirreldude]

Hi all,

After resolving a few issues with my Crack + Speedball build, it worked well for several months. This week I suddenly started experiencing loud popping in the right channel after the unit has been on for ~10 to 20 minutes. It starts as a soft rustling that builds in volume until it finally discharges with a loud "pop," and then goes quiet. Again, I only hear this distortion in the right channel, including the building static sounds. So far I have tried swapping both tubes, disconnecting the source, and tightening the screws that hold everything to the plate. Are there any other suggestions about what to do next?

Thanks,
Karl

 

[Paul Birkeland]

Reheat your solder joints, there's likely a loose one.

-PB

 

[squirreldude]

Paul, I reheated the solder joints and I'm still getting the pop after running for a few minutes. I can't seem to make it pop by tapping on the wood or the plate, but it will continue to pop every 10-15 minutes if I keep the amp on.

I know reheating solder is a common fix, but I think it's entirely unacceptable that I'm still busting out the iron to troubleshoot an amp that I've sent in to be serviced. If there's any guarantee on the BH service repair, I'd like to know how it might apply to this situation. What I'd really like is to drop it in the mail and have you take another look for components that could have been damaged by my faulty transformer. Let me know what you think, and feel free to PM me.

Karl

 

[Paul Birkeland]

I apologize, I did not remember that we had your Crack in for servicing.

Before sending it in, it would also be responsible to try a different set of tubes, just to eliminate that as a variable in the situation.

-PB

 

[squirreldude]

Today I tried two input tubes and two power tubes, and each configuration continued to show the same symptoms.

 

[Paul Birkeland]

Let me know if you still have the packaging we sent you, if so, we can get you a UPS label on Monday and you can return the amp to us to check out. 

-PB

 

[squirreldude]

Hey Paul, I do not have the packaging that came with the repair order. I do have access to loads of bubble wrap and cardboard boxes at work, or I can pick up whatever I need at my local UPS store. Though, one thing I will definitely need is the packing instructions.

 

[Paul Birkeland]

We will send you a new box.  Pleas retain this one if possible for any future shipping.

-PB

 

[Grainger49]

There is a good post on "Packaging Bottlehead Products For Shipping" somewhere on the site.  Hopefully it wasn't dumped in the latest update. 

 

[squirreldude]

We will send you a new box.  Pleas retain this one if possible for any future shipping.

-PB

Thanks Paul, I'll make sure I keep this one.

There is a good post on "Packaging Bottlehead Products For Shipping" somewhere on the site.  Hopefully it wasn't dumped in the latest update. 

You must be referring to this: http://bottlehead.com/packing-your-bottlehead-gear-for-shipping/
This is very similar [if not identical] to the instructions that come with the repair service kit. I definitely found the info helpful; good to know its posted on the site for future reference.

 

[Grainger49]

Thank you!  That is just what I was thinking of. 

The pictures have been dropped somewhere in the transitions.  They would be a great help if they were linked again.

 

[squirreldude]

Hey all,

I sent the amp to Paul and he wasn't unable to reproduce the popping symptoms. It behaved perfectly fine for him during the week-long visit and we began to suspect interference at my house. However, when I got the amp back in the mail this week, I discovered that the right channel is now totally dead! I swapped tubes, sources, and headphones, but I believe the problem is in the amp. I am including my voltage checks below, since some of them turned out way off from the expected range.

1 163
2 168
3 0
4 168
5 77
6 0
7 162
8 0
9 106
10 0
11 0
12 0
13 170
14 0
15 187
16 0
20 0
21 206

a
1 78
2 0
3 1.5
4 0
5 0
6 158
7 0
8 14.3
9 0

b
1 164
2 169
3 163
4 77
5 170
6 106
7 0
8 0

 

[Paul Birkeland]

Hello Karl,

So sorry to hear of these issues.  The voltages indicate that one half of the 12AU7 isn't conducting.  This can happen from shipping damage to the 12AU7, a bad solder joint between A4 and A5, damage to one LED, or a tube socket issue.

We can get the amp back in the shop to sort this out for you if the issue is not immediately obvious and easily resolved.

-PB

 

[squirreldude]

Thanks for the ideas, Paul. I'll give it a go after work today, but what exactly is a tube socket issue? Should I be looking for something obvious like a disconnected pin, or should I do resistance checks across the socket somehow? All I can think of is simple visual inspection.

 

[Paul Birkeland]

If you wiggle the 9 pin tube and things suddenly are OK, that might point to an issue with the tube socket.

-PB

 

[squirreldude]

Paul,

I noticed that one of the two LEDs on the 9 pin socket is out. Now that I think about it, I'm pretty sure it was unlit during the voltage check yesterday. I wiggled the socket and the light came on briefly, but I haven't been able to get it back on since then. During the time it was lit, voltage checks went back to normal. I tried different tubes again and reheated the joints on the 9 pin socket with no luck.

What do you think?
Karl

 

[Paul Birkeland]

We'll get it back in the shop and have a look.

-PB

 

[squirreldude]

Hey Paul, just checking in since I haven't heard anything in a while. Should I be expecting a UPS shipping label in the mail from BH, or am I expected to cover shipping from my end? As an alternative to shipping the whole amp, it might be faster and cheaper if you're willing to send me the socket and/or LED directly.

*Edit: I just received notice from Eileen that UPS will be coming to pick it up tomorrow. Thank you.

 

[Paul Birkeland]

Hello Karl,

I was able to measure an internal short between pins 8 and 9 on your 9 pin socket, which would explain the issues you were having.  With some proper jostling of the socket, the short could be made to go away or return, so the reasonable assumption is that there is some kind of conductive debris lodged between the two ceramic halves of the socket causing considerable chaos.

I replaced this socket and all is well with your amplifier.

-PB