Radio Road

Scott 350D?

124.171.142.252

Timbo in Oz

A

In Reply to: RE: Why hum? Why now? posted by torc on August 10, 2019 at 04:37:26

It's possible that the selenium rectifier is going off. Or a cap is fading.

But, clean and tighten all connections, at both ends.

And then take out and replace all the valves, after cleaning the pins. I'll assume they're all novals!

If hum's still, have someone replace the rectifier with something quiet, soft-recovery and high voltage! And, check the filter caps, too.

IMO Mapleshade should have replaced it back when.

Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger

Follow Ups:

RE: Scott 350D? - torc 18:58:03 08/12/19 (1)
Thank you. A cleaning - one tube at a time - is the place I'll start.

David
- If it were me, I'd also replace the selenium rectifier diode. - Timbo in Oz 20:23:40 08/12/19 (0)
  A soft-recovery ss diode with a high voltage rating.
  
  Eli Duttman's posts cover this.
  
  Warmest
  
  Tim Bailey
  
  Skeptical Measurer & Audio Scrounger
RE: cleaning the 'valves' (tubes, in 'murrican parlance) - mhardy6647 19:46:43 08/11/19 (1)
I've 'fixed' many malfunctioning (elderly) FM tuners by cleaning pins and/or sockets on the tubes, indeed! That said, for the OP's benefit: if you decide to go this route, remove, clean, and reinsert tubes one at a time . There are numerous carefully tuned circuits in an FM tuner; each circuit is tuned to the tube in that section. In many tuners, there are multiple 'instances' of the same tube type (e.g., 6AU6). Inadvertently 'swapping' different tubes of the same type between sockets may profoundly, and likely negatively impact performance of the tuner.

all the best,
mrh
- 'Usage and abusage' by Eric Partridge?! - Timbo in Oz 21:14:58 08/12/19 (0)
  So, 'valve' is more descriptive, and apt. :-) and ;-)!
  That selenium diode (rectifier) should go, too!
  
  Warmest
  
  Tim Bailey
  
  Skeptical Measurer & Audio Scrounger
  
  Edits: 08/12/19

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