RF gain control on AR88 not working - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Station X · 20th Sep 2023, 12:03 pm

Good to know it's working again. Be sure to make a good job of resoldering R56 or you could be saying goodbye to your output transformer should you use the set with headphones.

Radio Wrangler · 20th Sep 2023, 3:45 pm

But before a new problem arises, have you done the due diligence on the DC blocking and tone correction capacitors?

Sorry for pestering but any of these wonder-components can destroy your audio output stage, both valve and transformer with a fighting chance at taking out the mains transformer. Now is the exact time you would want to travel back to after the event, if you could hitch a ride on a passing time machine.

David

G6Tanuki · 20th Sep 2023, 6:34 pm

And while you're in there, consider doing my output-transformer-saving mod using a couple of wire-ended NE-2 neons across the primary too....

Neons are cheap; replacement output trannies for the AR-88 are not.

Silicon · 21st Sep 2023, 12:49 am

You also need to find out why the negative bias voltage is so high.

Alan Bain · 26th Sep 2023, 10:54 am

In case anyone finds it useful - here is a clear scan of the CR88 wiring diagram. I have no idea where this came from originally as when I was fixing my AR88 I had to rely on the hard to read one from BAMA.

This morning the cat knocked down a file which contained details of projects I had worked on long ago as a student and in it there was an AR88 manual and this original sheet of wiring diagram.

Uploaded as zip to stop resolution being reduced!

Alan

20th Sep 2023, 12:03 pm	#21
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 20,655	Re: RF gain control on AR88 not working Good to know it's working again. Be sure to make a good job of resoldering R56 or you could be saying goodbye to your output transformer should you use the set with headphones. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

20th Sep 2023, 3:45 pm	#22
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,239	Re: RF gain control on AR88 not working But before a new problem arises, have you done the due diligence on the DC blocking and tone correction capacitors? Sorry for pestering but any of these wonder-components can destroy your audio output stage, both valve and transformer with a fighting chance at taking out the mains transformer. Now is the exact time you would want to travel back to after the event, if you could hitch a ride on a passing time machine. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

20th Sep 2023, 6:34 pm	#23
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,460	Re: RF gain control on AR88 not working And while you're in there, consider doing my output-transformer-saving mod using a couple of wire-ended NE-2 neons across the primary too.... Neons are cheap; replacement output trannies for the AR-88 are not. __________________ I played a blank tape at full volume. The mime-artiste who lives next door complained.

21st Sep 2023, 12:49 am	#24
Silicon Nonode Join Date: Jun 2007 Location: Coulsdon, London, UK. Posts: 2,004	Re: RF gain control on AR88 not working You also need to find out why the negative bias voltage is so high.