Right channel intermittently working

[Petricore]

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

 

[Paul Birkeland]

I would start with a voltage check.

 

[Petricore]

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?

 

[Petricore]

Also, now that the amp has been on a couple hours, without messing with anything both channels sound good and even.

 

[Paul Birkeland]

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. 

 

[Petricore]

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&currencycode=USD

Thanks!

 

[Paul Birkeland]

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.

 

[Petricore]

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?

 

[Doc B]

Do reflow the terminal that PB mentions before you consider replacing the jack. We can provide a replacement if you need one.

 

[Paul Birkeland]

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!

 

[Petricore]

Thanks for your patience and clear responses. I'll look into this and let you know.

 

[Petricore]

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

 

[Deke609]

Maybe post some detailed pics of the headphone jack wiring and the pot wiring.

cheers, Derek

 

[Deke609]

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

 

[Petricore]

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.

 

[Paul Birkeland]

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)

 

[Petricore]

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.

 

[Deke609]

Post some pics of the headphone jack wiring from lots of different angles.

cheers, Derek

 

[Petricore]

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).

 

[Petricore]

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