Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

RCA R-73 RESTORATION
#29

I am wondering if you can't just replace the chokes with just plain resistors.  RCA used these a lot in earlier biased "power detectors" but have not used them in later radios, especially those using diode detectors.  These RFCs are in the plate and coupling circuits from the 1st AF Amp to the interstage transformer.  Iam pretty sure that the output stage is Class A Push Pull.  If the secondary of the antenna transformer is good, just connect a long wire antenna to the grid cap of the 1st RF Amp, at least to test the radio.  I won't bet my life on it but will bet lunch off the (non-existent) McD's $1.00 menu that the radio will work in that manner if nothing else is wrong.

Below is a section of the R75A schematic showing differences in the detector and audio section. 
[attachment=28025]
 

Note that L12 is not in this circuit.  The detector circuit has been rearranged from diode biased 1st AF Amp to a much more standard AF Circuit with a more standard volume control.  This will also allow you to input an external audio signal.  You will likely need to keep the original volume control circuit as it works by adjusting the bias on several circuits, in conjunction with AVC. in later radios with single end AF Output and RC Coupling between the 1st AF and Output, there is no RF Chocke in the audio circuit.  This is my rationale for suggesting replacing L11 and L12 with resistors and seeing what happens.  The fact that the output tubes are 2A5s and not 47s does not really have a bearing on this issue.  In fact, 47s can be replaced by 2A5s without much modification other than the tube socket, wiring in the cathode at the center tap and possibly the cathode bias resistor.

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards, 

MrFixr55


Messages In This Thread
RCA R-73 RESTORATION - by morzh - 02-19-2023, 05:11 PM
RE: RCA R-73 RESTORATION - by Brad Winder - 02-19-2023, 07:25 PM
RE: RCA R-73 RESTORATION - by morzh - 02-19-2023, 08:32 PM
RE: RCA R-73 RESTORATION - by David - 02-19-2023, 08:39 PM
RE: RCA R-73 RESTORATION - by GarySP - 02-19-2023, 10:03 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 02-19-2023, 10:20 PM
RE: RCA R-73 RESTORATION - by radiorich - 02-19-2023, 11:49 PM
RE: RCA R-73 RESTORATION - by morzh - 02-20-2023, 09:50 AM
RE: RCA R-73 RESTORATION - by Eliot Ness - 02-20-2023, 11:28 AM
RE: RCA R-73 RESTORATION - by morzh - 02-20-2023, 02:03 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 02-20-2023, 03:15 PM
RE: RCA R-73 RESTORATION - by Arran - 02-20-2023, 03:41 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 02-20-2023, 08:02 PM
RE: RCA R-73 RESTORATION - by Ron Ramirez - 02-20-2023, 08:44 PM
RE: RCA R-73 RESTORATION - by GarySP - 02-20-2023, 11:19 PM
RE: RCA R-73 RESTORATION - by morzh - 02-21-2023, 01:08 PM
RE: RCA R-73 RESTORATION - by Arran - 02-21-2023, 04:45 PM
RE: RCA R-73 RESTORATION - by morzh - 02-25-2023, 08:24 PM
RE: RCA R-73 RESTORATION - by GarySP - 02-26-2023, 01:54 PM
RE: RCA R-73 RESTORATION - by morzh - 02-26-2023, 03:03 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 02-26-2023, 10:42 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 02-26-2023, 11:02 PM
RE: RCA R-73 RESTORATION - by Arran - 02-26-2023, 11:22 PM
RE: RCA R-73 RESTORATION - by morzh - 02-26-2023, 11:31 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 02-27-2023, 01:01 AM
RE: RCA R-73 RESTORATION - by radiorich - 02-27-2023, 02:25 AM
RE: RCA R-73 RESTORATION - by morzh - 02-27-2023, 09:19 AM
RE: RCA R-73 RESTORATION - by Arran - 02-28-2023, 05:48 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 02-28-2023, 08:24 PM
RE: RCA R-73 RESTORATION - by morzh - 03-01-2023, 08:39 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 03-04-2023, 11:19 PM
RE: RCA R-73 RESTORATION - by radiorich - 03-04-2023, 11:50 PM
RE: RCA R-73 RESTORATION - by morzh - 03-05-2023, 01:44 PM
RE: RCA R-73 RESTORATION - by morzh - 03-05-2023, 09:58 PM
RE: RCA R-73 RESTORATION - by morzh - 03-05-2023, 11:10 PM
RE: RCA R-73 RESTORATION - by radiorich - 03-06-2023, 08:57 AM
RE: RCA R-73 RESTORATION - by RodB - 03-06-2023, 09:37 AM
RE: RCA R-73 RESTORATION - by morzh - 03-06-2023, 11:11 AM
RE: RCA R-73 RESTORATION - by morzh - 03-06-2023, 12:54 PM
RE: RCA R-73 RESTORATION - by morzh - 03-06-2023, 01:06 PM
RE: RCA R-73 RESTORATION - by RadioSvit - 03-06-2023, 01:13 PM
RE: RCA R-73 RESTORATION - by RadioSvit - 03-06-2023, 01:23 PM
RE: RCA R-73 RESTORATION - by morzh - 03-06-2023, 02:31 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 03-06-2023, 06:04 PM
RE: RCA R-73 RESTORATION - by Chas - 03-06-2023, 07:48 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 03-07-2023, 06:21 AM
RE: RCA R-73 RESTORATION - by morzh - 03-07-2023, 11:53 AM
RE: RCA R-73 RESTORATION - by morzh - 03-09-2023, 04:31 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 03-10-2023, 01:10 AM
RE: RCA R-73 RESTORATION - by RadioSvit - 03-10-2023, 05:24 AM
RE: RCA R-73 RESTORATION - by morzh - 03-12-2023, 04:38 PM
RE: RCA R-73 RESTORATION - by morzh - 03-14-2023, 10:32 PM
RE: RCA R-73 RESTORATION - by RodB - 03-15-2023, 10:14 AM
RE: RCA R-73 RESTORATION - by morzh - 03-15-2023, 02:34 PM
RE: RCA R-73 RESTORATION - by morzh - 03-18-2023, 01:43 PM
RE: RCA R-73 RESTORATION - by morzh - 03-19-2023, 09:52 PM
RE: RCA R-73 RESTORATION - by morzh - 03-20-2023, 09:16 PM
RE: RCA R-73 RESTORATION - by Arran - 03-21-2023, 12:48 AM
RE: RCA R-73 RESTORATION - by morzh - 03-21-2023, 08:34 AM
RE: RCA R-73 RESTORATION - by MrFixr55 - 03-22-2023, 08:09 AM
RE: RCA R-73 RESTORATION - by Ron Ramirez - 03-22-2023, 10:10 AM
RE: RCA R-73 RESTORATION - by morzh - 03-22-2023, 01:30 PM
RE: RCA R-73 RESTORATION - by Arran - 03-22-2023, 04:59 PM
RE: RCA R-73 RESTORATION - by morzh - 03-22-2023, 07:22 PM
RE: RCA R-73 RESTORATION - by morzh - 03-22-2023, 11:30 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 03-23-2023, 05:45 PM
RE: RCA R-73 RESTORATION - by Ron Ramirez - 03-23-2023, 07:18 PM
RE: RCA R-73 RESTORATION - by morzh - 03-23-2023, 08:47 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 03-24-2023, 08:35 AM
RE: RCA R-73 RESTORATION - by Ron Ramirez - 03-24-2023, 09:10 AM
RE: RCA R-73 RESTORATION - by Chas - 03-24-2023, 10:19 AM
RE: RCA R-73 RESTORATION - by morzh - 04-01-2023, 05:20 PM
RE: RCA R-73 RESTORATION - by morzh - 04-01-2023, 05:26 PM
RE: RCA R-73 RESTORATION - by morzh - 04-08-2023, 04:04 PM
RE: RCA R-73 RESTORATION - by morzh - 04-12-2023, 09:18 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 04-13-2023, 09:47 AM
RE: RCA R-73 RESTORATION - by morzh - 04-13-2023, 10:31 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 04-14-2023, 07:28 AM
RE: RCA R-73 RESTORATION - by morzh - 04-14-2023, 06:48 PM
RE: RCA R-73 RESTORATION - by morzh - 05-07-2023, 02:31 PM
RE: RCA R-73 RESTORATION - by morzh - 05-21-2023, 03:45 PM
RE: RCA R-73 RESTORATION - by MrFixr55 - 05-21-2023, 11:09 PM
RE: RCA R-73 RESTORATION - by morzh - 05-22-2023, 01:16 PM
RE: RCA R-73 RESTORATION - by RadioSvit - 05-22-2023, 01:40 PM
RE: RCA R-73 RESTORATION - by morzh - 05-22-2023, 02:19 PM
RE: RCA R-73 RESTORATION - by morzh - 05-27-2023, 07:46 PM
RE: RCA R-73 RESTORATION - by Joe Rossi - 05-27-2023, 08:15 PM
RE: RCA R-73 RESTORATION - by morzh - 05-27-2023, 09:24 PM
RE: RCA R-73 RESTORATION - by Ron Ramirez - 05-27-2023, 09:29 PM
RE: RCA R-73 RESTORATION - by morzh - 05-27-2023, 09:41 PM
RE: RCA R-73 RESTORATION - by Steve Davis - 05-27-2023, 10:20 PM
RE: RCA R-73 RESTORATION - by morzh - 05-27-2023, 10:29 PM
RE: RCA R-73 RESTORATION - by Arran - 05-28-2023, 12:54 AM
RE: RCA R-73 RESTORATION - by RadioSvit - 05-28-2023, 05:14 AM
RE: RCA R-73 RESTORATION - by morzh - 05-28-2023, 09:55 AM



Users browsing this thread: 12 Guest(s)
[-]
Recent Posts
My last cabinet for this year
They are a nice looking radio, Stromberg. I have a small tabletop octagon-dial one. It sounds surprisingly nice. And t...morzh — 09:40 PM
Philco 41-608 changer coupler
Different years but the same idea.morzh — 09:38 PM
My last cabinet for this year
That’s a beauty! :thumbup:klondike98 — 09:24 PM
Philco 41-608 changer coupler
Hi Morzh, I've searched using Mondial as the user name with various keywords such as 'coupler', 'motor', 'idler', 'p...alangard — 08:31 PM
Philco 16B Parts
I think the chassis is painted.morzh — 08:13 PM
Philco 38-2 Automatic Tuning
Honestrly, the original is quite acceptable and, it seems to me, can be cleaned.morzh — 08:11 PM
Philco 41-608 changer coupler
Mondial left a thread about remanufacturing thois type coupler.morzh — 08:09 PM
IF can wire size and Rubber mounts?
Are you talking about rewinding or rewiring? For rewiring, meaning runnin wires to the coil from other components, the ...morzh — 08:08 PM
12' Philco
I wonder who would be able to "no stoop" with this one.morzh — 08:05 PM
IF can wire size and Rubber mounts?
Hello PHORUM members, I am still working on restoration of my PHILCO 37-640.  I want to start with rewiring the IF ca...georgetownjohn — 06:32 PM

[-]
Who's Online
There are currently 3390 online users. [Complete List]
» 2 Member(s) | 3388 Guest(s)
AvatarAvatar

>