[NJARC] Grounding question

[Scott Roberts]

This may sound like a simple question, but I do need an answer, although I am pretty sure I know it already...

I am working on my BC-348-P, which I got at the swapmeet back in August or September at Info Age.

I had thought I had corrected all the modifications made to the set, and returned it to original shape. However, I still get a loud hum over any and all settings. I have been starting to check voltages and resistances at the tubes with the I-56-A test set.

Anyway, I just found a change I missed- The dial lamp circuit has been heavily modified- The power in lead has been moved from the AVC-Off-MVC switch, front wafer, position 1, and moved to the  VT-86(217, First I.F.) tube socket terminal 7. Continuing through the circuit, the original series arrangement of the lamps has been changed to parallel, and resistor 503(the flat 60 ohm dial lamp resistor) has been bridged across with a piece of bus wire.

Could these changes, having been left unnoticed & intact, be the cause of the overriding hum? I am about to restore the circuit, as I would anyway, but wanted to see what you guys think.

I'll let you all know the results(hopefully positive & hum free) after i complete it and test the unit again.

I am still not sure the neon tube in the oscillator plate voltage regulator, (id 218, 2J991, or 2V991, JAN-991) is operating properly, and wonder if it could be related to either, or both issues- the convoluted lamp wiring, or the hum...

Thanks!
Scott