Crackling and static in the right channel [resolved]

[Paul Birkeland]

OK, there are wires going from B7/B8 to the power transformer.  If both tubes are not glowing but the high voltage remains, then one of those wires is not well connected or broken.

[Cowwe]

Right, that makes sense. I am going to reflow B7 and B8, since it's pretty tricky to tell whether the joints look good.
I will check voltages again afterwards and report back.

[Paul Birkeland]

Don't ignore that it may well be the wires at the power transformer that feed B7/B8 that are loose.

[Cowwe]

Yes, of course.
After reflowing B7 and B8 the voltages measure within good ranges and the amp is working.
I'm going to let it run like this for some time and see whether that fixed the issue.

[Cowwe]

I have a brief update, bringing both good and bad news about my situation.
The good news is that reflowing B7 and B8 seems to have fixed the issue with my amp dying and coming back alive. I have kept it on for a number of hours and the amp stays on.
The bad news is that I am back to fighting with the the crackling noise in the right channel.
Last night I went through the usual chopstick test, and I have found that lightly pushing on the black wire to terminal 3 sends static noise on both channels. I don't know whether this could be the culprit for my issue, but I will be starting from reflowing there.

[Paul Birkeland]

I would carefully examine the black wires that meet at the headphone jack.  It's extremely common for builders to not capture both of them with solder adequately, and this can cause a lot of issues.

[Cowwe]

I went and soldered terminal 3. Now the joint looks nice and well connected and doesn't react when I try to mess with it with a chopstick.
Unfortunately this didn't solve the noise issue.
The joint at the jack terminal with two black wires connecting honestly looks very good to me. The two wires seem to be covered in solder and they don't make any static or crackling when I mess with them.
I have spent a long time trying to find the joint that's causing the noise but I haven't been able to get anything out of it. I can't even tell whether the noise changes by rocking the tube anymore.
My voltage readings are the following:
1) 79,6   2)172,5    3)0    4)172,6   5)79,7
6)0    7)105,4     8)0     9)106,8     10)0
I have noticed that there is a 1,4v difference between terminal 7 and 9. Could this be an hint?

[Cowwe]

For what it's worth, I have tried recording the crackling. https://voca.ro/1j7PsZyGOoYt
Please try to ignore the loud clock sound in the background and the quiet static, which comes from the microphone itself.

[Cowwe]

I just went ahead and reflowed most of the joints in the amp, basically only leaving alone the 9 pin socket and the connection around the power switch. I made sure to pay particular attention to the octagonal socket and the part where the black wires meet at the jack. Nonetheless, this did not solve anything. Right now I am at a loss on what to do, as the amp is still unusable as it is.
One thing that keeps puzzling me, is that a couple of weeks ago the noise did react to moving the 6080, and that after messing with it for a bit the amp did work flawlessly for a period of time. It only came back after I reflowed the bad joints at B7/B8, which fixed my issue with the amp turning itself off.

Hoping that you won't mind the wall of text, I'm going to reorganize the main results from my testings so to have the situation as clear as possible:

-The crackling noise appears soon after the amp is on. I would say after about 15 seconds, whereas when the problem first appeared it only started after a longer period of warm-up.
-The noise is exclusively in the right channel. If I just barely unplug my headphone jack I can hear it in both (since that's when the headphones normally play in mono).
-The noise does not depend on whether I have the RCA's connected or not, and it does not change depending on which wall outlet I plug it in (not even a different house).
-I have tried multiple driver and power tubes and all of them have the same issue. Wiggling either tube does not have an audible effect, and the socket and tube pins look rather clean.
-The noise doesn't change depending on volume. It's always there at the same volume.
-The chopstick test did not reveal any weak connection. Even lightly pulling/pushing on wires I couldn't notice any audible reaction.
-Applying pressure on the chassis in several different positions did not reveal any audible changes either.
-I have reflowed the majority of joints, including those that looked alright to my eyes, and the voltages always measure within the standard values. The one thing I noticed, as I mentioned in a previous message, is that there is always a discrepancy of about 1.5V between terminals 7 and 9, whereas the other terminals (for example 1 and 5) mirror each other much more closely.

[Paul Birkeland]

I would try this: https://forum.bottlehead.com/index.php?topic=11676.0

The 1.5V difference between 7 and 9 is not anything concerning.

[Cowwe]

I have already applied the modification with the diodes and it served its purpose in eliminating the noise coming from my pc, as I posted in the beginning of this thread here are a couple of pictures. https://imgur.com/a/7aKU7dQ
My problem is present even if no RCA's are connected.

[Paul Birkeland]

That sounds more like an interference issue, like some WiFi enabled device that's too close to the Crack.  This is a similar noise to the USB computer noise, but if it's present with no cables attached, then it may well be coming through the air.

[Cowwe]

I honestly find that very unlikely though. I have used the amp for around two months with no noise outside of those coming from my source, which was fixed with the diode modification as a breaker. I haven't added any new device to my setup, and even moving to a completely different house kilometers away from my place the noise was the same.
Plus, a couple of weeks ago I could actually interact with this noise through wiggling the 6080 tube, and had two days where it was completely gone.

[Cowwe]

I am most likely grasping at straws right now since I am running out of ideas, but I have noticed that my wirewound resistors are not turned the same way they are in the manual's pictures.
Could this make a difference of some sort?

[Doc B.]

If you could make the noise stop by wiggling a tube in the socket it would seem prudent to clean the tube pins and socket. Try Caig Deoxit.