Help with wiring a GEC GEC75 telephone - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Henmond · 31st Jan 2022, 12:04 pm

Maybe I have been particularly unlucky, but both of mine cause an annoying ~50 hz hum in the reciever. Both are made by A. P. Besson, and both different ages.

Nickthedentist · 31st Jan 2022, 3:18 pm

Nearby SMPS or Low Energy bulb etc??

ISTR a BT memo about some being prone to RFI, the cure being to try one of the other makes which were around at the time (blue or black?).

Dave Moll · 31st Jan 2022, 3:33 pm

The big advantage of the red variant is its flexibility as far as fitting into different handsets is concerned.

I wonder whether wrapping the inset in metal foil might help to block RFI. Unfortunately, earthing the foil isn't very feasible.

Henmond · 31st Jan 2022, 8:10 pm

I don't think it is RFI, I've tried it with as many electrical devices switched off as possible, yet it still occurs, so unless it comes from the ATA itself I'm not sure where.

I remember reading somewhere that moisture ingress over time causes a failure that results in this humming.

31st Jan 2022, 12:04 pm	#21
Henmond Triode Join Date: Jan 2022 Location: Stratford, Taranaki, New Zealand Posts: 30	Re: Help with wiring a GEC GEC75 telephone Maybe I have been particularly unlucky, but both of mine cause an annoying ~50 hz hum in the reciever. Both are made by A. P. Besson, and both different ages.

31st Jan 2022, 3:18 pm	#22
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,861	Re: Help with wiring a GEC GEC75 telephone Nearby SMPS or Low Energy bulb etc?? ISTR a BT memo about some being prone to RFI, the cure being to try one of the other makes which were around at the time (blue or black?).

31st Jan 2022, 3:33 pm	#23
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,130	Re: Help with wiring a GEC GEC75 telephone The big advantage of the red variant is its flexibility as far as fitting into different handsets is concerned. I wonder whether wrapping the inset in metal foil might help to block RFI. Unfortunately, earthing the foil isn't very feasible. __________________ Mending is better than Ending (cf Brave New World by Aldous Huxley)

31st Jan 2022, 8:10 pm	#24
Henmond Triode Join Date: Jan 2022 Location: Stratford, Taranaki, New Zealand Posts: 30	Re: Help with wiring a GEC GEC75 telephone I don't think it is RFI, I've tried it with as many electrical devices switched off as possible, yet it still occurs, so unless it comes from the ATA itself I'm not sure where. I remember reading somewhere that moisture ingress over time causes a failure that results in this humming.