Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: Petricore on July 30, 2020, 03:48:18 AM
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I've had my crack kit for over 9 years, I've upgraded to speedball, I've rolled numerous tubes and I've upgraded the volume knob and added resistors to give me more volume range.
I've recently run into an issue where the right channel is really really faint or non existent. This usually only happens when I turn it on. Sometimes I can turn it on and leave it for a couple hours and its working normal, sometimes it works normal the first time. More often than not lately it doesn't work when I turn it on. I've rolled tubes again to see if that helped and so far it hasn't.
Looking for places to start troubleshooting the problem.
Thanks
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I would start with a voltage check.
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Paul, thanks for the quick response.
I'm good with soldering and handy with a volt ohm meter. Can you tell me which voltages you suggest I start with? Or should I get the final voltage check sheet from my initial build (if I still have it) and check them all? Would I check them from the initial build or from the Speedball upgrade sheet?
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Also, now that the amp has been on a couple hours, without messing with anything both channels sound good and even.
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I would measure the voltages at terminals 1-10. There should be at least one voltage that's way off when that channel fades out.
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Nothing was out of whack with the terminals 1-10. After I moved it around the problem switched channels. I started playing with the headphone jack and got all sorts of noise and the problem seemed to move back and forth.
I ordered a new headphone jack but just noticed (remembered...built my crack almost 10 years ago) that there are 6 poles and 2 resistors wired to the current headphone jack. Can I wire the headphone jack I got in still? If so do I remove the resistors or put them inline still?
I got this jack: https://www.mouser.com/ProductDetail/switchcraft/152b/?qs=IF7nv7MIRJ1SluLsIALMEg%3D%3D&countrycode=US¤cycode=USD
Thanks!
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That jack is not suitable for use in the Crack.
The junction of the black wires on the headphone jack is a place where I often find issues when performing repairs. Generally I see one of the wires will be loose and wiggling around while the other is properly captured in solder. I would look for that, I'm not so sure I would just replace the jack.
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Oh bummer, I thought I read in a different thread in the crack Forum Doc recommending this one for the alum chassis crack.
Anyway I can reflow all the joints on the current one and try again. If it is in fact a bad headphone jack, where can I find a suitable replacement?
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Do reflow the terminal that PB mentions before you consider replacing the jack. We can provide a replacement if you need one.
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Oh bummer, I thought I read in a different thread in the crack Forum Doc recommending this one for the alum chassis crack.
It puts the chassis in as a conductor of signal current. You can use the jack, but you'd need to figure out some insulating hardware so that the metal body of the jack doesn't touch the chassis plate, or figure out a way to insulate terminal 3 from the chassis. You will also lose the ability to have the output shorted with no headphones plugged in, which is a nice feature of Crack 1.1.
Anyway I can reflow all the joints on the current one and try again. If it is in fact a bad headphone jack, where can I find a suitable replacement?
NYS212
I would take your needlenose pliers and pull on the wires going to the HP jack. I bet one of the black ones will move more than it should, or possibly just pull all the way out!
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Thanks for your patience and clear responses. I'll look into this and let you know.
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OK I resoldered my headphone jack and I reflowed the solder on the potentiometer as well (replaced it a year or two ago). I can still move the headphone jack while its playing and have the volume change.
After it sat cold all night I fired it up and the "dead" channel was less quiet, but did take an hour or so to warm up before it started working normal in each channel again.
I put the multimeter on after turning it on, below are current readings.
Terminals
1:75
2:179
3:0
4:179
5:75
6:0
7:86
8:0
9:88
10:0
Any additional help would be appreciated :)
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Maybe post some detailed pics of the headphone jack wiring and the pot wiring.
cheers, Derek
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I started playing with the headphone jack and got all sorts of noise and the problem seemed to move back and forth.
If wiggling the headphone cable plug makes the problem worse, the plug might be your culprit. Have you tried a different set of headphones?
cheers, Derek
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Yeah, the headphone cable itself doesn't seem to be the culprit, I can put it in my other amp and move it all around an not have a single issue.
I have also tried another set of cans and have the same issue with this amp. Appreciate the questions. I'll see if I can get a picture posted soon.
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And we will assume that you're not using a 1/4" to 1/8" adapter in the Crack but not your other amps. (These are a common point of failure)
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I am using an adapter, always have with my DT880s (like I never unscrew it, its lived on them).
I bought a replacement and somehow the bias seems worse now, like the left can is louder and the right can is still softer.
I'll try to get ahold of another good pair of wired cans to test, I'm starting to suspect I need to recable these cans. I can wiggle it with the new screw on adapter and it crackles and sound changes.
I can also plug this exact setup into my DAC, which also has a built in amp and the cans sound level. Which is why I haven't been suspecting cans yet.
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Post some pics of the headphone jack wiring from lots of different angles.
cheers, Derek
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Also, oddly, the time to evening out seems shorter, they are already closer than when I tested a few minutes ago.
Also again plugging into my solid state amp, I can't reproduce the issue.
I'm starting to wonder about the potentiometer I replaced a year or two ago (tho it functioned fine until recently if that's the case).
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Post some pics of the headphone jack wiring from lots of different angles.
cheers, Derek
Right, I keep forgetting sorry. I'm down one hand currently so things are taking a lot more time.
I'll try to get some photo assistance this afternoon :)
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After 9 years of use it's not unreasonable for the contacts in the jack to have got tired/broken/moved out of kilter. I would have just changed it out for a replacement BH one in the first instance. It's a good solid regular jack not a precision built for life item.
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Which one would you replace it with?
It also kind of would make sense that warming it up physically could help the contacts if they are just slightly out of whack.
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Tell us about the replacement pot. What precipitated replacing the pot, and what pot did you use as a replacement.
I wouldn't just toss the jack, I have seen those jacks at 20+ years of age still working nicely.
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I replaced with a Audio Note 100K Ohm Stereo Balance Potentiometer with some advice I got here. I also added 33K and 75K resistors from another post here.
I replaced the pot because at low volumes one side of my headphones got really quiet, which I read was an issue with the stock pot.
I added the resistors to give me some more headroom on the volume knob.
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You can't just put a balance pot in place of the volume pot. You can add the 33K and 75K resistors to the stock pot to even it out. The balance pot needs to be removed, it will not function
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Right I apologize, I incorrectly bought a balance pot and then exchanged it for the same product in a volume pot. I remember when I installed the balanced pot it broke everything. Sorry for the out of order info there. I can try to find the stock pot if me replacing it is what is suspect here.
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At one point in this thread, you were certain that you had a bad headphone jack, and I provided you with a part number for its replacement. Did you end up replacing it?
I still believe you have a loose connection in your amp. The other possibility would be a failing tube (certainly a possibility after 10 years), but this would be clearly reflected in the voltage checks I had you do, and your tubes still seem to be working great.
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I haven't replaced the headphone jack yet, you seemed pretty sure it wasn't. Definitely not trying to pick a fight, I appreciate your help. I'm also trying to be careful with my amp and not just replace things on a whim.
I will order a new jack and see if that helps!
As far as the tubes go, I have 3 aftermarket tubes and the stock tube and all 4 have the same issue.
I am happy to provide more info and be helpful, I've been too busy to keep up with it lately so I've just had the amp on all day/night and the issue doesn't seem to be happening. I'll report back after I get the new jack.
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Well, I can tell you that I repaired a Crack yesterday that came with a long note from the customer about how he had a dropping channel and resoldered his connections half a dozen times but couldn't figure out what was going on.
The wire from B6 to terminal 9 was loose...
If you can physically see damage to your headphone jack, then replace it. If you plug in your headphones and you can see that the contacts aren't lifting off the shorting positions, then this is another reason to replace the jack.
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Replaced the jack. Much much better engagement with the headphones, but sadly the problem still exists. Really loud in one channel and quiet in the other until the amp warms up.
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I'm doing a little revamp to the workings of the repair service, but when it's available again you are welcome to send your amp in. I still believe there's a 99% chance you have a flaky solder joint or broken wire.
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OK let me know when its up and what the costs are.
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I've been working around this by keeping the amp on. After a week+ of being on the issue popped up while I was using it. I turned the amp off and haven't used again since.
Really weird.