[mikethedruid]

Thanks Ron ! You sure are a wealth of information. I have the RCA service manuals downloaded in PDF, but the picture of my set isn't very clear. None of them really are, but one of the consoles seems to show something similar to what Dan posted

[Ron Ramirez]

Here's a picture at the Radio Attic Archives which should help more than anything:

https://www.radioatticarchives.com/radio.htm?radio=6071

That T8-18 looks like it has a good original finish, and the decals are correct.

Oh, I really don't know that much about RCA. You can credit the late Doug Houston's influence (plus I have what was once his set of RCA Red Books). He loved his RCAs just as much as his Philcos. Because of his influence, I now can appreciate mid-30s RCAs, and I now understand why he spoke of them so favorably. Of course I also have my own memories of one of my very first antique radios, an RCA 5T1 which was an amazing performer for a five tube set with no RF amp - on the AM band, anyway (as I recall, it wasn't so hot on SW).

And you're right, a lot of the photos in the Red Books are tiny and it is difficult to make out details.

[mikethedruid]

I've still been busy with this radio. I couldn't leave the the rubber wiring alone. Some of it I KNEW was quite brittle, and might cause a problem in the future, so over the past few nights I have been busy replacing almost all of it with cloth covered of the same color.  In one place there were 2 white wires that are stuffed in behind the band switch between it and the chassis. I am sure they are routed that way to keep noise off the lines since they are in the audio circuit. I used white plastic covered wire to replace those.

[Image: https://66.media.tumblr.com/088ad047c767...1_1280.jpg]

I was also unsatisfied with the cabinet. There were places, like the top, where most of the original varnish was actually gone once I had cleaned the cabinet and removed the dead finish and dirt. The sides and front were better, but still uneven. Today I took the cabinet out and stripped it using furniture stripper and steel wool, rinsing it well after with mineral spirits. That got rid of all the dead finish. From what I could see when the cabinet was still wet, it is going to look quite good with new finish applied. I'm going to use tung oil, rub on several coats, perhaps sanding with 1200 grit between the last few. I am very familiar with this finish since I have used it in my violin making. Yes, that is another hobby of mine. I have made several violins, and also repair them. I am not a great player, but I do enjoy playing.

[mikethedruid]

Tonight I gave my T8-18 its first live test. First tested it with the 5Z4 removed. All the tubes except the 6E5 are metal, but the dial bulb llit properly, and the 6E5 filament glowed properly. I then plugged in the 5Z4 and turned it back on. The radio came to life. It receives a few stations on broadcast band with just me as an antenna. Since the radio does not currently have a dial, I expect it will arrive in a few weeks, I am not able to do any further work such as alignment at this point. Still, no smoke, no explosions, no fire, and the radio basically works. All good signs. I may yet have to replace some of the mica caps, but, so far so good.

[mikethedruid]

Did more work on the T8-18 today, what little I could anyway. I found a dead spot down near the 600 end of the dial per instructions, and then set about aligning the IF. I was rather surprised to find it was WAY off. I had to loosen the screws on the condensers that show on the bottom of the chassis a couple of turns each to get the set to align at 460KC. Both the IFs are now as close as my ears and my signal generator can get them. Sadly, my frequency counter has been acting crappy lately, I don't know why. Fortunately my old Heathkit signal generator is quite accurate, so I was able to do the alignment. Now I'll have to wait for the dial to arrive before I can go further.

[mikethedruid]

"The night time is the right time." That saying sure does hold true for radios. I decided to see how my old RCA would do this evening. With just a VERY short antenna, my signal generator turned off actually, and hooked to the antenna lead, I was able to pick up lots of stations on the broadcast band, among them the ball game on 700 AM, WLW out of Cincinnati. That came in remarkably clear. Next I tried band B, which runs from 1.6 MC to 6 MC. I was able to get a few stations on that band also, among them WWV at 5 MC very clearly. Then I tried band C, which runs from 5.5 MC to 18.5 MC. I could receive stations in several places on that band, especially those around 9 to 10 MC and the ones below, between 7.6 and 5.5 MC. This all bodes VERY well. One sad note. The old paper cone of this receiver, which was originally cracked long ago and repaired, and had some more cracks again when I received it, which I repaired, cracked yet again while I was setting the IF. Fortunately I could still use it to test the radio, but the sound quality is crap. I am going to order a new cone for it, and fix it myself this time. I replaced the cone on my old Philco 37-61, and it worked like a champ. I have written a dealer on eBay who sells lots of different cones to get his advice on which one of his items would be best for my use. Until them this one will suffice for the alignment work I have left. I can hardly wait until my dial arrives from Radio Daze, so I can get that done. Today I also ordered decals from Radio Daze. I got the sheet with 4 different styles of RCA Victor on it, one of which I have seen on several sets of my model at the bottom in the front. I have seen a number of sets with various decals for the band. One is like the T7, one is just letters A, B, C, but most of the pictures I have seen of this model have NO DECALS AT ALL! I have actually ordered the decal set for my RCA 18T, which is a later set, to cut and use. It has the letters for the bands, as well as all the words for "POWER," "VOLUME," "TONE," "RANGE," and "TUNING." It will require a bit of fine cutting to get just right, but will look good, although probably not original. I actually wonder if some sets didn't have any decals at all. Mine had no signs of them at all before I did my first cleaning, I looked. Now I am going to relax for the rest of the night, drink iced tea, and watch a western movie on YouTube. I've earned it.

[mikethedruid]

Sometimes you can't rest until you have figured something out. I noticed a discrepancy between the schematic and the way the radio is actually wired. It is wired as the layout diagram shows, NOT as the schematic, both in the RCA manual and the Rider manual shows! I checked this out tonight. I wired in the components that are missing in the layout diagram and tested the radio. It made no difference at all in the functioning. I suppose this is a modification made after the schematic, but before the layout diagram, but was not noted in Rider's where the layout diagram appears. In the time since I first redid this part of the chassis and tonight, I received 2.2 MEG 3 watt 1% resistors, so I replaced the 2 MEG + 220K I had previously installed when I returned the radio to the way the layout shows.
[Image: https://66.media.tumblr.com/523066d01314...o1_640.jpg]

[Image: https://66.media.tumblr.com/d1ee1cdd0656...2_1280.jpg]

VERY INTERESTING !

[mikethedruid]

More testing and fiddling. After playing with this radio some more, I realized that the magic eye does NOT work nearly as well with it wired as the layout shows, it works best wired as the schematic shows, much more sensitive, so I re-wired it again, back to how the schematic shows, and now the magic eye seems to be working more sensitively. Today I put the old dial back on the radio and began to do the alignment. I set the shortwave bands as per the instruction, and also set the broadcast band per the instructions. The magic eye is actually quite a help with this, it is a good way to double check my ears. Now it is set, with frequencies matching the dial. Tonight it will be interesting to see what I can receive.

[Jake Blake]

"I had some in GT type, but these are in an RCA, so I had to order the metal type since this radio needs them for shielding."

I was tempted to order glass replacements for the Motorola 51X16.  How does one know when it's required to use the metal types?   Is the RCA T8-18 unique from this standpoint.  I can figure the purpose is shielding, but why do we have a choice?

[Ron Ramirez]

Because there were radio manufacturers (Philco and Zenith chief among them) who refused to go down the RCA/GE metal tube route. They chose to use Sylvania-built ST glass tubes with octal bases instead.

With the possible exception of a very few Simplex-designed small Philco table model radios (Philco ultimately bought controlling interest in Simplex), I can't recall a single Philco radio which ever used metal octal tubes.

[mikethedruid]

Two ways, one more accurate than the other. If there are no signs of a tube shield on the chassis for the RF, mixer-oscillator, or both if separate, IF, and detector-AVC tubes, then it probably wants metal tubes. The other way is to look at the schematic, and see if the shield pin is connected to chassis ground, or is used as a floating tie point. If a tie point, it uses GT, if tied to chassis it uses metal. Pin 1 is usually the shield pin in metal tubes. To be certain look at the data sheets for the tube number with and without the G or GT.

[Jake Blake]

" They chose to use Sylvania-built ST glass tubes with octal bases instead."

Thank you Ron. 
This actually may answer another question I had, about which tubes were original in my Motorola 51x17.  I originally guessed the one Sylvania it has is a replacement. . . now it's looking like just the opposite... possibly it's the only original !  That gives me a clue to which one most likely just died.  I just eliminated the rectifier with a switch-out.

"To be certain look at the data sheets for the tube number with and without the G or GT."

Thanks Mike.   The schematic for that Motorola calls for all GTs.  Interesting.

[Ron Ramirez]

Mike raises a good point. In 1937 Philco models, the tube shield bases were wide enough that any tube could be used, whether ST glass, metal, or the (then-as-yet-undeveloped) GT styles. If the sockets of those tubes have pin 1 grounded, one may use a metal tube.

Now, Philco closed that loophole in their 1938 model radios and went back to using their 1936 model year tube bases, through which only ST type "G" octal bases will fit. This is why we find so many mangled 1938 model year tube bases these days - so repairmen later on could force a metal or GT tube to go into the tube base. And, yes, some tube bases were even ripped out by "repairmen" for this purpose.

Many RF and IF tubes need to be shielded, as well as some 2nd detectors and audio preamp tubes, depending on their physical location on the chassis.

Footnote: Until Philco bought controlling interest in Lansdale Tube Company (and even after that), Sylvania made tubes for Philco, even stamping them with Philco's brand name instead of Sylvania's.

[Jake Blake]

So , how is this RCA coming Mike?  

[mikethedruid]

The alignment is done. It works pretty well with a crappy indoor antenna, I can get WCBS in New York, WOR in New York, WLS in Nashville, and WLW in Cincinnati, and stations all across the dial on AM, as well as a lot on short wave so I figure it will do really well with my outdoor antenna. I got one of the cones for the speaker I ordered, but it is a little too deep. I guess I'll have to wait to see if the other one I ordered is a better fit. If worse comes to worse, I know how to modify them so they will fit, but I'd rather not do that unless I absolutely have to. I am still waiting for my dials to come in. Yes, I said dials. I have the one I ordered from Radio Daze on order, but have not heard that it has been shipped. They did ship my decals today though, so I should be able to put them on the cabinet, and finish that soon. I also used Ron's tip about dials on eBay, and ordered one for my T8-18 which I found. I will have to drill and trim it, but if it gets here quickly, what the heck. Even with the shipping it was a lot less than the one from RD.