[Arran]

Ed;
  I can have a look in the U.S RCA manual if you like, I think it has a wiring diagram in it for your set that will show what is supposed to go where physically around the tone switch, or is it a potentiometer? Interesting that your RCA used one of those, I though that tone switches were more of a Philco thing, although I noticed that my new Canadian Pye radio uses one too. I never liked the tone control switch idea, it limits your choice to whatever tonal "ranges" the engineers thought best back in whatever year they were designing the set. Maybe whomever was in there before didn't like the factory choices and decided to experiment with different value caps or resistors? I always preferred the potentiometer types though I do like the arrangement several Canadian Westinghouse sets where they have a switch for selecting bass, treble, and a mid range, but also a potentiometer, combined with the Magnavox speakers they used, and the heavy wood cabinets they housed their sets in, made for a nice sounding radio.
Regards
Arran

[EdHolland]

Hi Arran,

Thanks - that would be helpful. The tone circuit is switched only, and operates in conjunction with a tapped 2 M Ohm volume pot.

The service details I found have a top-side diagram and a schematic but no wiring diagram. I traced the pot and switch wiring, and put 2+2 together about the clipped wire ends found in that area which would account for the missing caps. The laborious part was figuring out which switch tag corresponded to the numbers on the schematic - espesicially when position #6 is shown not connected, but has a wire and a cap. It's a trick - it is a dummy tag used as a tie point!

I think it all makes sense, but additional info would be very welcome please

Cheers

Ed

[Arran]

Ed;
  Send me an email address, via a P.M, and I will see if I can find the diagram and scan it.
Regards
Arran

[EdHolland]

P.M. sent

[Arran]

Sorry Ed; I forgot to look tonight, but I will look that up tomorrow.
Regards
Arran

[EdHolland]

No worries, no rush

[Arran]

Ed;
  I looked up your 110K2 in the 1937-42 U.S RCA red book and I was mistaken, unlike the Canadian RCA models for those years there is no wiring diagram or parts placement diagram. This would be one of the few occasions where the Philco manuals from the era are actually better. What you have out of Riders and Beitmans is pretty much what's in RCA's red book, so unless RCA sold a stand alone service folder for this set this is pretty much all that you are going to find.
Regards
Arran

[EdHolland]

Hi Arran,

Thanks for checking anyway.

I think, now, that with a good understanding of the circuit, determining the tone switch terminal numbering, and the evidence of clipped out caps that it will be fairly easy to put this back together with the right components in the appropriate places.

...and to think I was being given a radio that needed no/little work.

Cheers

Ed

[Ron Ramirez]

Ed

I have scanned and posted the 110K and 110K2 service manual here.

As Arran said, there is no under-chassis wiring diagram or parts placement diagram as with older RCA service liteature, but you may find it useful anyway.

[EdHolland]

Ron,

Thank you very much

Regards,

Ed

[EdHolland]

I had an opportunity to put some more time into this radio today. Returning to the "messed about" tone and volume circuit, I remembered where things were left off and retraced the circuit again. The work to reconfigure it to the paper schematic made sense, and I was able to complete it easily. From there, attention turned to the audio circuit, and all caps and resistors replaced in the output and phase splitter sections.

The old resistors were interesting... of 3 220K composition types tested, 2 were at 250K, and one completely open circuit. Two 1k types were around 4K, as was a 2.7K part. The 10K I removed measured around 14K. Lastly, a 220K had been replaced (leads clipped long and the new part hooked in to them ) with a 470 K.

This poor old set was in quite a state. Getting better all the time.

[EdHolland]

A little more work yesterday, resistors and caps - working my way back though the RF section.  I had to extend the leads of some capacitors to reach between tags - the old components were that much bigger.

Still checking parts as I go. Nearly all the resistors now are well out of range, sometimes measuring double or more the marked value, and in many cases do not give stable readings. Caps are often worth a look too, just for grins. Many seem OK on the mulimeter cap test, and measure high megohms or over range for leakage, but I would not trust them at high voltage 

There are a couple more caps, and a handful of harder-to-reach resistors left before this chassis is finished. After that, clean and check the speaker and repair/restore the cabinet finish.

[EdHolland]

Moving forwards steadily. I'd just started at the bench this afternoon when the phone rang. My wife was stuck - the Range Rover (Classisc) had died just as she reached the barn... Cranking, but no start. I guessed the problem, and was ready, drove down, changed the distributor rotor arm for the one I replaced 3 years ago.

WrWrWR Vroom!

Job done, I returned quickly to the bench before I forgot where those parts went, which I had just removed... Another little subsection completed.

[EdHolland]

All the resistors are done

There's one more cap yet to do. It's an orange drop from the other restorer, so I've no idea if it is the right value. Easy to reach, but I ran out of time.

Next up, to replace the bulb wiring, and the four wire harness to the speaker plug.

[Arran]

Ed;
  Does the speaker cable use cloth or rubber/gutta percha covered wire? The RCA A-30 I'm working on used cloth covered, and I think it's still good and flexible, but the speaker is in the cabinet which is tucked in the corner in another room, I've been using the speaker out of an RCA A-22 table set for testing, the wires in the antenna cable are bad of course.
Regards
Arran