UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Quad II problem

Richardgr · 25th Nov 2022, 9:59 am

Is it worth pointing out that the issue with the OPT might be a symptom of another issue? Could be that a coupling capacitor was leaky or a tube was gassy, and a tube ran away. Do you know if the output tubes are OK?

There is a guy I met over here (Stockholm) who is sitting on a stash of 6000 KT66 maintenance pulls from Sverige Radio (who ran a sQuad of Quads), but nowadays we do not have the luxury of affordable KT66 replacements. Hence it is not worth being too much of a purist under the hood if that means you are implementing safety and resilience improvements.

To that end, there are the fuses, chassis earth point, possibly blocking capacitor on the input, separate cathode bias for the output tubes and I added a screen grid stopper as well so I could use cheaper NOS tubes (5B/255M).

25th Nov 2022, 9:59 am	#57
Richardgr Heptode Join Date: Oct 2019 Location: Täby, Sweden Posts: 709	Re: Quad II problem - Rectifier blowing (GZ32) Is it worth pointing out that the issue with the OPT might be a symptom of another issue? Could be that a coupling capacitor was leaky or a tube was gassy, and a tube ran away. Do you know if the output tubes are OK? There is a guy I met over here (Stockholm) who is sitting on a stash of 6000 KT66 maintenance pulls from Sverige Radio (who ran a sQuad of Quads), but nowadays we do not have the luxury of affordable KT66 replacements. Hence it is not worth being too much of a purist under the hood if that means you are implementing safety and resilience improvements. To that end, there are the fuses, chassis earth point, possibly blocking capacitor on the input, separate cathode bias for the output tubes and I added a screen grid stopper as well so I could use cheaper NOS tubes (5B/255M).