Blackstar HT Stage 60 / Need help on strange noise issue

[FredPhil]

I fixed my previous measures for voltages, we're getting closer to the same voltage for R142 and R143...

What kind of bulb is installed?

ECC82 (12AU7)

Between pins 3 and 8 of the panel the connection at 0 ?

You mean for V3, voltage between 3 and 8? I'm not sure I understand your question.

[x-pro]

C123 is in place. Replace C118 and C116 with simple ones, not electrolytes. If there are no others. You can do it on wires, but insulate the leads well.

[x-pro]

ECC82 (12AU7)


You mean for V3, voltage between 3 and 8? I'm not sure I understand your question.

not anymore.

[FredPhil]

Thing is, I don't have spare capacitors. I have to order them and wait for them to be delivered before testing again...
It seems that this test shows that at least one of the 3 cap leaks. So I'm going to replace all 3 anyway, with the same specs. Is there something else I should test right now? Or order something else just in case? I will pay more shipping fees than items anyway ;-)

[x-pro]

troubleshooting is a sequential process

[Helmholtz]

A leaky ecap used as coupling cap can produce noise (as can a leaky board or leaky glue).

[FredPhil]

I'm ordering the caps, will keep you informed. Thanks again for the help on this very sequential process

[g1]

I think the idea is to first mount new caps lifted off the board with full length leads or wires. If that solves it, then mount them back on the board. If problem comes back, the board is causing the problem, not the components.
If you mount them right on the board straight away without this step, it is out of sequence.

[Helmholtz]

Film caps are always a better solution than ecaps.
Only problem is the larger footprint.

[FredPhil]

I think the idea is to first mount new caps lifted off the board with full length leads or wires. If that solves it, then mount them back on the board. If problem comes back, the board is causing the problem, not the components.
If you mount them right on the board straight away without this step, it is out of sequence.

Do you mean that if it works with caps off the board but doesn't with caps on it, that suggests the caps make the board overheat and somehow get faulty?

[x-pro]

I suggested using film capacitors instead of electrolytic capacitors and connecting them to the board with wires. The point is that they have large dimensions and may not fit in place of the old ones.

[g1]

Do you mean that if it works with caps off the board but doesn't with caps on it, that suggests the caps make the board overheat and somehow get faulty?

No, I was thinking there may be a fault on the board itself, with voltage leaking to the caps, like was mentioned about the glue. But I was mistaken as mounting the caps either way, the leads/wires would still be contacting the leakage/voltage.
xpro explained the real reason in post #116.

[FredPhil]

OK thanks, Anyway I ordered elctrolytic caps, so I'm going to mount them "normally" to check if the cause of the issue was that one of them was leaking.

[Mick Bailey]

Have you eliminated board leakage as per post #47. You can keep replacing parts and continue to have faults if the board is leaky. The earlier amps started to leak in just over a year of use.

[FredPhil]

Have you eliminated board leakage as per post #47. You can keep replacing parts and continue to have faults if the board is leaky. The earlier amps started to leak in just over a year of use.

I tried to do what I could, but there were no obvious evidence of leakage. What concrete tests would you suggest to rule out this problem?