Dsl15 bias issue

[Arbutt]

Morning. OK a Dsl15 on the bench blown fuse fs1. Tested tubes gone bad. Replaced tubes new tads 6v6. Turned on can see on switch on that too hot.
Found at the lowest I can only get to 40ma and rising. Then I saw that the 2 x 100k had been piggyback with 47k s. Removed and retest. Still the same really

B+ starts at 420 ish and drops too 385v
Bias voltage - 27v
-72v at point of d1/2
Tried 2 sets of good tubes
Removed all the ecc83
Heater on ecc83 6.5v dc
With all tubes out b+ is 424v

@ 420 v I should be around 20ma for 70%

Any experience chaps, care to help
Arbutt.
Will try and get map over shortly

[Jazz P Bass]

Schematic attached.

[Arbutt]

Thank you. I'm only on the phone at present and you beat me too it.

[Jon Snell]

What happens when you reset Trim 1 & 2. The bias voltage should turn to cut off point or at least very nearly but, if C9 is low value, there will be a lack of -ve DC for the bias.
C9 should be of a suitable type and value!

[Arbutt]

Hi Jon. Not with the amp at present. But with the bias at the lowest position. I have about 40ma on test points and that is after a very short time - 27v on the tube base.

[g1]

-72v at point of d1/2

What is DC voltage at anode of D2 ?

[Arbutt]

Hi g1. From memory it was - 72v.
Many thanks

[Arbutt]

Morning. We'll this morning I followed the advice and changed c9 and while I was there. Changed the 10uf 160v. All done.. Til next time.
Arbutt

[pdf64]

It’s good that this isn’t a manifestation of the conductive pcb issue.

[g1]

changed c9 and while I was there. Changed the 10uf 160v.

Do you mean C15 22uF 160V ?