Rca 9-t-79
 

I'm guessing that's the model number. Going off of this post. The chassis is still in my trunk. (Get to that in a bit.)

I went to the estate sale expecting the tv to either be sold or be too expensive, hoping they'd have some other old goodies. Well they really had nothing else of interest... besides a small handheld vacuum cleaner and a pair of pinking shears that I've been wanting for the odd time that I'm sewing something.

The tv was priced at $80. The conversation went thusly:
Me: "So it's half off tomorrow?"
"Yes, what are you interested in?"
"TV"
"It's $80, I'll take $70."
"Meh."
"How about $50?"
"Ok~"

It's complete, minus one or two tubes. It was filthy inside, nasty black sooty electronics dust. The crt plug cap thing is broken badly, but it was still plugged in. I called a friend to help move it, while I waited, I dismantled the set right in the middle of the estate sale. I figured having it in bits would be much safer, and easier - to move only an empty cabinet. Plus my friend is a klutz.

Dismantling was easy. I used the toolkit I keep in my trunk. Chassis was missing two bolts, other two were loose. It just got me covered in filth. Good thing I was in my work clothes.

The crt tests zero. 19AP4. Filament lights and getter flashes look fine. I'm going to say it's asleep and leave it the hell alone. I learnt my lesson already. I did clean it though. Mostly for practical reasons of not having a large filth-encrusted item in the middle of my clean bedroom.

The cabinet is in amazing shape, except the feet which look like they may have been wet once upon a time. They had it up on bricks in the basement. Not really that bad, I can probably cover up the damage. The top has clearly been re-coated. There's still scratches and handwriting under the clearcoat. Doesn't look bad though.

Speaker is there. Cone looks fine. Grille cloth is fine, too.

This will be a project for later. I have too many things cooking already. Incidentally, I already have a very similar set, with a rectangle tube. That cabinet had been cut in half. Presumably the chassis will be very similar... if I need some parts.

---

Also, I promptly repaid the favor for my friend helping me to move this thing. He called me later in the day asking advice for a microwave he was repairing (appliance repairman). So I went over and helped figure that out. That was hard. But once I wrapped my head around the operation of the machine, it was very simple.

That thing was the "Bee's Knees" back in the day. Nice that you have saved it.

It's from that period that RCA was using their air core flyback. I've tried to locate some insider engineering document explaining why they had gone to that system, but so far no luck. I have a fascination with any set that used that system, especially one with a 19" CRT. It'll be fun to see that one fired up.

Not much RCA engineering info survived the GE buyout IIRC.

Is the cabinet really that heavy that 1 person can't move it with the chassis and CRT pulled out?...A console usually has to be a LOT bigger than that for me not to be able to move the empty cabinet solo.

Oh that's interesting. What's that all about, then? Anything to do with the metal CRT? Because it needs to have a HV capacitor - since the jug isn't its own capacitor like a glass tube.
It is pretty heavy. Imagine a real hardwood dresser without the drawers in it. I could certainly *move* it by myself, but carrying it up stairs and out to a truck is a two man job. I could've maybe tackled it by myself if I had a dolly, AND some pieces of 2x4 to fill the void in the bottom so the dolly could grab it. Or load it upside down if I wanted to screw up the wood. But why should I make my life any more difficult than it is already?

No I don't think it had anything to do with CRT type. They made several models, I believe all in 1950 (including some with all glass CRT's), that all shared that same flyback type. And apparently licensed it to other manufactures, for instance I have a 1951 Emerson with the same circuit.

I have a pretty good idea of what it weighs. I had a similar-sized RCA before...Empty cabinets usually ain't too bad even in midsized drawerless dresser weight...
About a week ago I carried the cabinet of this beast out of the basement and to the garage in one go without assistance and without damaging it or the house.
http://videokarma.org/attachment.php...9&d=1572756305

Some day your back could remind you. Now may be good time to find some young gal to help you lug those sets around. ;)

OK, now that you guys are mentioning this "air-core" flyback transformer from RCA and that it was liscensed to other companies, did my Meck TV I am currently working on use that "air-core" flyback system by any chance?

I'm curious because some of the symptoms you guys have described that system having when it starts failing is the same exact symptoms my Meck TV is having in regards to the flaky high voltage and not very bright picture and what not... :scratch2:

That is on the to do list just past get my own house. When I have a girlfriend I want to make sure I keep the TV moving burden off of her as much as possible.... growing up my dad never did any of the handyman stuff willingly and often botched it if left alone... that stuff primarily fell to ma (who has health problems partially because of that) and me as I got older...As far as I'm concerned a man shouldn't off load all man's work to wife and kid.
Although I suppose on the bright side there are few home improvement tasks I'm not experienced doing or atleast generally informed about...
Last time the family moved we didn't hire movers...I was sore for a month but built like a brick wall for a good year after that. :D

So I just finished testing the tubes. The ones in it, anyway, it's missing about 4 little ones. About half of them tested bad or right in the questionable zone. Do tubes go to 'sleep' like CRT's do? I tested known-good tubes to check the tester, and they all tested good.

Or are all the bad tubes the 'fallout' from the set being run with bad/shorted capacitors, etc?

1920s tubes are more prone to sleeping. When newer tubes are weak they usually are just bad.

Some tubes in a set can be cap casualties...though it isn't always recent. Some sets when the owner decided it was no longer worth repair would run their sets till they literally dropped dead and sometimes would even periodically beat the dead horse to see it it'd go a bit further after collapsing...

Some sets were also less picky about tube quality than others...some of my daily driver sets that get hours per day to hours per week after a few years of that on a service I'd sometimes find many tubes VERY weak despite the stages they drove still working decently (changing those would wake up performance often).

This is the style of flyback I was referring to this TV having. Kind of amazing they were able to light up a 19AP4 CRT with it. It'll be fun to get that set operational.

https://live.staticflickr.com/65535/...9f3a1843_z.jpg

https://live.staticflickr.com/65535/...13123af7_z.jpg

I once had a Capehart-Farnsworth that had a flyback like the one in the picture.

Air Core H.O.T.
 

I think the reason for the early air core H.O.T.'s is that the insulating materials were not developed enough to use iron core H.O.T.'s. The static sets and early lower high voltage CRT's were able to use iron cores simply because the HV was lower and they could insulate them from arching. When they went to larger CRT's requiring higher high voltage the iron core transformers would arch to the core. Even though using air core transformers made it more difficult to create the required HV it also made arching less likely. That's just my guess, may be completely wrong. Thanks guys!

Dennis

Were other sets using ferrite cores or iron cores at that time?
If ferrites with the desired properties were not available then, an air core may have been used because the available ferrite or iron (powdered iron?) cores were too lossy.

Also, I don't know if the resonant frequencies of the primary and secondary were tuned at that time the same way they were later: 3rd harmonic tuning or 5th harmonic tuning makes the secondary ring at an odd multiple of the primary flyback pulse, which produces a high voltage pulse with a flatter top instead of a pure sine wave. This makes the high voltage supply droop less with increasing current, because the rectifier is seeing a more constant average voltage over time with a varying current.

I put the whole shebang on my workbench and brought it up on a variac. I got filaments but nothing else. I tested power in and out of the 5U4. Power in, nothing out. It tested poorly on my Hickok earlier. I pulled it out and the getter flash looks light gray instead of normal, which I'm pretty sure it looked normal before. Either this tube went to air slowly or maybe it was cooked. Which makes sense, because after I changed it, the set pulled 300 watts, I heard the HV try to come on a couple times, and two of the three big can capacitors got really hot. So I'm going to order some caps.

In related news, the crt tests near-zero on my tester. However it tests the known-good Admiral's tube at just above one. I've figured out that all the resistors in my tester have drifted high, and doesn't make the 300v it should be making. I'll be getting resistors for that too.

Also, there are two capacitors to ground from line and neutral on the plug. Do those need to be special capacitors to handle line voltage (all the time)?

Fixed my crt tester (I think), picture tube tested dead. I replaced 2 cans' worth of filter capacitors and fired it up.

It's kinda blurry, have the focus magnet at max. Could be the yoke is not all the way on. (Have a feeling someone's going to say tube is bad, I mean, probably, but it lights up, so...) CRT appears to have a spot burn. It's not terribly bright, but I'd think watching in a lit room would be marginally possible. Couldn't hear the HV or vertical at first and I was kind of disheartened. Maxed the horizontal hold and then I could hear it. Vertical is really quiet though. Played with the ion trap for about 10 minutes - thinking I wasn't gonna get any light on the tube - before finding out that it likes hanging out all the way back on the plug cap... which is unfortunate because it's completely broken. I tried flipping it but it's still as far back (single magnet).

So far, not bad for all original wax paper bombs and half the tubes being bad or marginal.

I replaced a CRT once that required the ion trap to be placed very far back. I tried all that you did, but it still wanted to be all the way back touching the base. The set worked well for years until it was replaced. I've always wondered what was different about this CRT. Was the electron gun not installed properly? Wrong electron gun assembly?

Could be your ion traps magnetism has weakened since new... I'd try another trap.

If the center spot on the CRT is only visible when the tube is lit, it's not a burn, but rather vaporized metal has been deposited on the back side of the phosphor. The deposited material is causing that area to shield the electron beam from lighting the phosphor. That's what happens if the set gets operated for a long time with the Ion trap improperly adjusted. That CRT seems to have fair brightness, although if it won't focus well it's possibly also the result of it being operated with the Ion trap improperly set. Once the electron gun aperture material becomes vaporized there's no way to fix it short of replacing the gun, otherwise you live with it as-is. If your high voltage isn't up to spec that could also be affecting the focus. I'd say you've got very good life signs considering the all original caps.

Check the voltage on G-2... if it is too low, electrons in the electron gun will be easier to deflect with a magnetic field, requiring a weaker or oddly located ion trap. :scratch2:

just a WAG,
jr

I thought I'd try my hand at actual diagnosis instead of using the shotgun approach. Main problem was no snow / no video coming through. Doing some voltage checks and found everything WAY out of line. Eventually traced it back to a main power resistor R125 on Sams, 4k 10w. It's mounted on top of the chassis behind the tuner. Wide open. My luck that I have 20 new 5k resistors and not one 4k. I put a 5k in there for the hell of it, it made no appreciable difference in the operation of the set and got VERY hot very fast. So now I'm thinking like there's something else shorted that burnt up the old resistor. Probably a capacitor lol. Also there's a resistor R131 8k 10w, that I cannot find for the life of me. Sams shows on the alternate chassis it may not exist, but it should on mine. However, Sam's schematic is preferential to the tv/radio model which is missing the end of the audio section and some other stuff.

Thoughts?

Also, digikey does not stock any 10w 4k, would 25w be ok?

As an aside, a week ago I found a Zenith console stereo in the trash. Someone ate the record player and trashed the cabinet, so I stole the tubes. The first one I pulled was a 6AU6, and I was happy cuz I needed one for this tv, but the rest I pulled were clearly more modern numbers. But with the help of a tube substitution book, apparently I can use 5 (for this tv) out of the 8 or so that I took. Yay!

>>SCHEMATIC<<

Most sets old enough to have primarily cardboard tube paper caps troubleshooting before shotgunning those caps leads you to just shotgun the caps more slowly/methodically and pull the hand full of resistors and misc parts you'd troubleshoot and change post recap into the process....

The best sets to do the kind of troubleshooting techs did when new are the 60s sets that still have most of their original caps good..