Crack 1.1 noise in right channel

[oguinn]

You might want to take a look at the lower lug of the potentiometer on the outboard side of the chassis. It looks like some of the insulation got melted to the lug, and maybe there's some stray solder there too.

[A Jedi]

Yup, I'm going back and hitting all the ones MAY be the issue. That one on the volume is the prime suspect. So much easier to see these things when you take pics and blow them up!

[Paul Birkeland]

The black wires on the headphone jack are suspect.  The black wires that meet on the headphone jack are also suspicious, and this is a joint where it's easy to get one wire soldered and not the other.

The red wire connected to 7U also looks like it might not be all the way soldered. 

[A Jedi]

Thanks, I'll look at those again. In the meantime I fixed the lower red on the potentiometer and a few other suspects but no improvement so far.

[A Jedi]

Went through all questionables and still no bueno. It's actually a little worse now. Very frustrating. I'll have to do the chopstick test.

[A Jedi]

I'm starting to think it may be a tube. The noise gets quieter after the tubes warm up.

[Paul Birkeland]

You can try leaving it on for a few days.  Often times when I have a tube that's making noises, it will stop after the tube has been brought up to operating temperature and left running for a while.

[A Jedi]

Cool, I'll do that.

I'm now 99% certain it's the 6080. Whenever a noise starts, if I tap it, noise goes away. It's as if something inside it goes into its resonance frequency and needs an external force to stop it.

[Paul Birkeland]

That could also be related to the solder joints on the octal socket or on the other end of components attached to the octal socket. 

[A Jedi]

It's possible. But man, I've been through all those joints 10 times. Will take another look tomorrow and maybe get lucky.

[oguinn]

You could test the tube theory with a new 6080 or one of the variants listed in the tube rolling thread. They’re not cost prohibitive. If you go that route give the current tube a few days’ worth of burn in while you wait.

[A Jedi]

The amp is on my desk next to my bed and last night when I went to bed and everything was quiet, I started hearing the noise. Nothing was hooked up to it - only power. Stuck my ear close to the chassis/transformer/6080 and could clearly hear it. So it's not just coming through the headphones (although it's louder there). So, got up this am and tightened all the screws to see what would happen - nadda. Will do the chopstick test later today and then order another tube. Dammit.

[A Jedi]

It's def the tube. I flipped it over and powered it up. Poked around every wire and joint and nothing made a difference. Back the right way up, a light touch with a pen tip on the 6080 and buzz stops. Ordered another tube....

[Paul Birkeland]

When you flip things over, gravity moves things around.  Last year I worked on a little Pilot EL84 amp that would work perfectly upside down, but would lose its ground connections when I flipped it over!

I would recommend hanging onto the 6080 you have just in case the new tube doesn't resolve the issue. 

[A Jedi]

Yep hanging onto it