Roberts RM40 AFC problem. - UK Vintage Radio Repair and Restoration Discussion Forum

G6Tanuki · 18th Mar 2023, 7:44 pm

A while back, I acquired a Roberts RM40, and did the usual safety/reliability reworking before loaning it to a friend.

She's now having issues with its AFC; she will tune-in a station with the AFC disabled [which is sensible] but on engaging AFC it will become noisy [like off-tune] and often latch-on to another station potentially two-channels-up from what she wants to hear.

Is this a sign of potentially-unbalanced diodes in the discriminator? I've already replaced the big non-intuitively-polarised electrolytic in the discriminator.

Where to go next? My friend is really more interested in DX reception on FM [I've already outfitted her with a tunable two-pole filter along with coaxial stubs to notch-out the more-intrusive BBC National noise below 95MHz, and she's got a 5-ele beam at 50-feet, aimed east]

Suggestions to help her get good reception of London free-radio stations from her abode in West Berkshire?

18th Mar 2023, 7:44 pm	#1
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Roberts RM40 AFC problem. A while back, I acquired a Roberts RM40, and did the usual safety/reliability reworking before loaning it to a friend. She's now having issues with its AFC; she will tune-in a station with the AFC disabled [which is sensible] but on engaging AFC it will become noisy [like off-tune] and often latch-on to another station potentially two-channels-up from what she wants to hear. Is this a sign of potentially-unbalanced diodes in the discriminator? I've already replaced the big non-intuitively-polarised electrolytic in the discriminator. Where to go next? My friend is really more interested in DX reception on FM [I've already outfitted her with a tunable two-pole filter along with coaxial stubs to notch-out the more-intrusive BBC National noise below 95MHz, and she's got a 5-ele beam at 50-feet, aimed east] Suggestions to help her get good reception of London free-radio stations from her abode in West Berkshire? __________________ I'm the Operator of my Pocket Calculator. -Kraftwerk.