This is my latest project, a 1938 RCA 99-T. Its a HUGE 9-tube table set with a rather complicated motorized tuner mechanism that allows you to tune manually or press one of the preset stations and an electric motor takes over to tune to that station. I sort of wonder about "robot" tuning and if it was a fad since Zenith and a few other brands had this feature at about the same time.



Someone had already done some work on the set. It has been refinished at some point and after a quick wipe down of Howards it looked pretty good because I hate refinishing stuff anyway.

After I removed the chassis I also saw that all of the electrolytic had been replaced. Thus I tested the set. It worked but the speaker made a horrible 'buzzing' sound. LUCKILY- the motorized tuning system works too. I was dreading having to work on it had it not. The electric motor has a sort of flywheel and a clutch that thrusts a lever into meshed gears. Its actually almost the same way a manual transmission on a car works.


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After playing the set and observing the speaker I saw that the cone had simply come loose from the outer edge of the frame. I re-glued the loose sections with wood glue. This stopped the buzzing sound. The set actually sounds quite nice.


I didn't want to leave any of the old caps in the set and thus proceeded to replace them. I don't have all the values needed but I had most. Whoever had worked on the set before did an extremely detailed and meticulous job detailing the work done. All of the caps I believe had been tested and their actual capacitance was written in pencil on the wrapper of each. Also, the edges looked to have been coated in some sort of clear varnish. At first I thought that they had been re-stuffed. I took a few apart and they weren't. So I replaced almost all of them save for the ones I am missing and will get later.



I used car wax and cleaner to polish up the transformer and tubes. This is the only set I own that for some reason has all metal tubes.

That is a very nice set, and has all the features in a tube radio that appeal to me.

A big table set, with a high tube count, and interesting motorized tuning circuit.

Nice job.

Interesting how that motor is made: when energized the field yanks the armature inside solenoid-style to engage the gears as the motor turns, as you mentioned. Sort of like a starter motor. All metal tubes would be the RCA "thing" in those days since they were pushing them. I put all metals except for the rectifier in an RCA of that era that I have.

I just did a K130 console with the same electronic tuning as yours.
Could not get mine to stop on the stations when using the electronic tuning.
Tried sharpening the pins and playing with the wires to no avail.
Any known secrets out there?
Thanks
murf

Yeah, that was sort of my conclusion too. Otherwise there isn't much too it. The big brass plate that has all the pressurized pins on top looks like a nightmare to deal with. Glad it works.



I have no clue. But the schematic I have contains details on how to set the stations. On mine I "think" the pins are actually movable. The set I have is a local one because its set to all local stations already. I'm not going to mess with it. When I get home I'll see if it says how to set these.

Easy to set.
The gap in between the 2 halves of the disc on the back of the chassis creates a break in the current,which causes the electric motor to stop.
The screws are spring loaded,so you just compress them and slide the plunger to the desired position.
I just can't get mine to stop on the gap.Even after sharpening the pins.
They get worn down over time.
Thanks
murf

Like most of us, I would have liked to get this set in original condition. That being said, you should first confirm that what replacements are in order, and if it's anywhere backwards in the B+ train, rip 'em all off and get new ones. Put in a 1 AMP FUSE. Next all the rest of the wax capacitors, and while you're at it, any associated carbon carbon resistiors, don't bother to measure, just replace. Blast out the controls and switches with deoxit, check your work, leave it dry overnight and bring it up slowly on variac and then tell us what happened.

I compared the schematic to the replacement electrolytics and everything was in order. Whoever worked on it before seems to have known what they were doing. Very neat, tidy work. Every single capacitor and resistor in the set has hand-written pencil notes showing what it is and what it tested as. Usually when I get a set that was worked on the work is often really crappy- as in a repairman slapped in some parts decades ago. At this point I need to replace the remaining caps as they were all .003, .005, .004, and .0001- all of which I am out of.

Thought you all would get a kick out of this. More for my own curiosity because I wanted to see the tuning motor in action. Feel free to turn off the audio as I realize I make a terrible narrator. ( can't film and talk at the same time)

That's pretty cool..

Just finished up the restoration. I was initially dreading this one as I expected it to be a rat's nest but actually it wasn't that bad. Anyway, here's a video showing the set in action, complete with motorized tuning .