Blackstar HT Stage 60 / Need help on strange noise issue

[FredPhil]

R154 : 2V
R153 : fluctuates a lot around 0-20mV

R150 and R154 read 265k (design is 260k)

[FredPhil]

Also please measure the voltages of R153 and R154.
Of course constant voltages and without signal.
And measure the ratings of resistors R150 R152, when the amplifier is switched off. You can do it directly in the circuit without unsoldering.

Double post, forget it...

[x-pro]

C116 and C123 check for leakage.
Of course, unsolder

[FredPhil]

These capacitors are glued to the board, how can I remove the glue without destroying anything? Gently using a cutter?

[Helmholtz]

C116 and C123 check for leakage.
Of course, unsolder

I don't suspect C123 as it's connected to a negative voltage.

[Helmholtz]

These capacitors are glued to the board, how can I remove the glue without destroying anything? Gently using a cutter?

Actually the leakage might be caused by the glue itself.
Try to lift from board using an X-Acto knife (scalpel).

[x-pro]

I don't suspect C123 as it's connected to a negative voltage.

agree

[FredPhil]

Removed all 3 capacitors and they all read OK... (1microF +/- 10%)

[Helmholtz]

Removed all 3 capacitors and they all read OK... (1microF +/- 10%)

It's about electrical leakage - not capacitance.
Leakage acts like a parallel resistor (often in the Megohm range) no longer allowing the cap to completely block DC.

With caps removed, measure the R143 voltage drop.

[x-pro]

It may show a normal value, but it may be leaking a constant voltage through it. This is called leakage. If you have a spare regular metal-film 1 µf common metal-film 1 µf at 450 V or more, make a replacement. Temporarily.

[x-pro]

maybe C118 is leaking?

[Helmholtz]

maybe C118 is leaking?

See post #90.

[x-pro]

See post #90.

Must have been slow internet. Didn't see post 90 before. Sorry.

[FredPhil]

All 3 caps removed from the board (C116, C123, C118)

146V on R142
149V on R143

SORRY, made a measuring mistake in this original post.

[x-pro]

good