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Old 5th Feb 2017, 7:08 pm   #125
Techman
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Join Date: Nov 2009
Location: Lincolnshire, UK.
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Default Re: Restore a Beau Decca

I've suddenly had another thought about something you MUST check!

While you've got it powered up with all the valves in place, check the voltage on the anodes of the two output valves (where R47 & 48 go to the valve base pins) to make sure it's near enough the same on each valve. Also check the voltage on the other end of both these resistors on the output transformer side. This will give us an indication of the continuity of both sides of the output transformer primary, the state of the two resistors and even any possible excess current that needs to be worried about when full power with all valves in place is eventually applied (although capacitor replacement will take care of that before then) - possibly even the state of the valves in comparison with each other.

A faulty mains or output transformer would be pretty much a show stopper at this stage, although I think you'd be very unlucky if this happened to be the case, so unlikely.

A last thought - without checking back so not sure if it does, but if there's any HL41 type valves in the earlier stages, these can sometimes develop a heater / cathode short causing bad, uncontrollable hum. Again, I've had this problem with these valves in the past, but I think you'd be unlucky if this were the case here. NB, a heater / cathode short in these valves can sometimes be cured by removing said valve and whacking it on a hard surface, but please don't try anything like that at this stage before checking input signal wiring and HT smoothing.
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