RCA AR88D receiver BFO. - UK Vintage Radio Repair and Restoration Discussion Forum

hammarlund 7 · 21st Dec 2015, 11:06 pm

I have an AR88D which works very well on AM, but the BFO is not working. It did work, but I use the RX very infrequently. I would appreciate some pointers.

Radio Wrangler · 21st Dec 2015, 11:51 pm

Valves are very reliable but are easy to swap. Do you have a spare 6J5 you can pop in to try as it's the quickest thing to try.

Beyond that, check the anode DC voltage, check the anode feed resistor, check the decoupling capacitor hasn't gone leaky. I'm away from my AR88 files so I can't be specific. Most probably it's findable from DC conditions.

David

G8UWM-MildMartin · 22nd Dec 2015, 1:34 am

The 6J5 may have developed what has variously been described as cathode poisoning or high cathode interface resistance (and it's not really of any practical help to argue about the inaccuracy of either term) through running without anode current. But a few hours' operation with the BFO and oscillator 6J5s swapped might rejuvenate it enough.

gezza123 · 22nd Dec 2015, 8:53 pm

There are two 6j5s in the set
V3 = RF osc that is under the tuner screening can.
V12 = BFO osc.
You can swap over these two valves to do a test, but please note! you must put them back in there original places, as this can alter the oscillator and your RF/Dial alignment.
I have also found if you swap out or change any other valve in these sets you have to realign them.
So please mark your valves/positions before you start to swap out any valve to test in an AR88D.
If this does not work then replace the valves back in there respective places
and carry out some tests as above.
Hope this helps gezza123.

hammarlund 7 · 22nd Dec 2015, 10:35 pm

Many thanks for all your help. I'll do as you suggest in both scenario and send results. H7

21st Dec 2015, 11:06 pm	#1
hammarlund 7 Triode Join Date: Dec 2015 Location: Ormskirk, Lancashire, UK. Posts: 13	RCA AR88D receiver BFO. I have an AR88D which works very well on AM, but the BFO is not working. It did work, but I use the RX very infrequently. I would appreciate some pointers.

21st Dec 2015, 11:51 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,876	Re: RCA AR88D receiver BFO. Valves are very reliable but are easy to swap. Do you have a spare 6J5 you can pop in to try as it's the quickest thing to try. Beyond that, check the anode DC voltage, check the anode feed resistor, check the decoupling capacitor hasn't gone leaky. I'm away from my AR88 files so I can't be specific. Most probably it's findable from DC conditions. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

22nd Dec 2015, 1:34 am	#3
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Re: RCA AR88D receiver BFO. The 6J5 may have developed what has variously been described as cathode poisoning or high cathode interface resistance (and it's not really of any practical help to argue about the inaccuracy of either term) through running without anode current. But a few hours' operation with the BFO and oscillator 6J5s swapped might rejuvenate it enough.

22nd Dec 2015, 8:53 pm	#4
gezza123 Heptode Join Date: Mar 2010 Location: Eastham, Wirral, Merseyside, UK. Posts: 788	Re: RCA AR88D receiver BFO. There are two 6j5s in the set V3 = RF osc that is under the tuner screening can. V12 = BFO osc. You can swap over these two valves to do a test, but please note! you must put them back in there original places, as this can alter the oscillator and your RF/Dial alignment. I have also found if you swap out or change any other valve in these sets you have to realign them. So please mark your valves/positions before you start to swap out any valve to test in an AR88D. If this does not work then replace the valves back in there respective places and carry out some tests as above. Hope this helps gezza123.

22nd Dec 2015, 10:35 pm	#5
hammarlund 7 Triode Join Date: Dec 2015 Location: Ormskirk, Lancashire, UK. Posts: 13	Re: RCA AR88D receiver BFO. Many thanks for all your help. I'll do as you suggest in both scenario and send results. H7