Magnavox CT-234-B chassis TV set. I think... - Videokarma.org TV - Video

nasadowsk · #1 10-02-2005, 04:33 PM

Ok, I picked up that REAL early Maggie the other day. Out in the middle of NOWHERE, Pa....

It's heavy table set - 85 lbs.

Removing the chassis is a fun task.

* Remove the screws. It won't come out.
* Pop the back. No interlock - it's on the HV cage cover.
* Hey! There's a few catches for the whole FRONT of the set!
* The front tilts out an inch, then lifts up, revealing the front of the chassis + CRT.
* Still won't come out. Bummer.
* Let's pull the CRT - it's easy, unhook the strap around it, undo the ion trap and connector at back - it slides right out. Easy. The strap is spring loaded, you just stretch it around the tub like a bungee cord.
* Two "hidden" screws in the corner release the chassis, finally.

The flyback looks like an early DuMont or RCA 630 type.

The CRT was a 12LP4 - the listed types are 10BP4, 10FP4, 12KP4. This was a Magnvox branded tube, but the quality looked a bit rough. The getter and base are still intact though.

The set appears to have 4 video IF stages, 3 audio IF stages, and a 1N34 vid detector. A single 5U4 powers it all.

Focus is via electromagnet.

I'll have to remove the HV box covers. It's *filthy* inside. The horz output, osc, damper, and rect are in there. All the usual suspects for an early TV - 5V4, 1B3, 6BG6, 6SN7.

Except for the recieving stages, there are few miniture tubes involved.

This set's weird - but it looks like it could be really nice once it's working. It's pretty service friendly one you figure out the trick to pulling the chassis - the HV box proveds a nice solid support to rest the chssis on it's side and as a bonus, the mounting tab on that side detaches so the thing sits flat!

Looks like the normal electrolytics and paper caps blown stuff - doesn't look too serviced though.

Replacing the 'lytics is gonna be 'fun'

Not much room to hide new ones - I might have to 'stuff' the cans. I wish someone made new, unstuffed cans that your could stuff, seal, and install. - saves having to cut the old ones open, which can be a pain in the you know what.

This set looks like it's gonna be real fun.

Anyone out there have the Sams? It's an early set pre 1950 or so. No Channel 1. if anyone finds something close, I'll scan the tube shart on it to doublecheck.

Thanks!

Chad Hauris · #2 10-02-2005, 05:41 PM

What we have done sometimes where absolutely original appearance is not needed above the chassis is to mount a small Radio Shack project box in the space occupied by the old caps, and then mount terminal strips in there and mount the new caps, and run the leads through grommets to the chassis through the old cap holes. We have done this on electronic organs where there was not enough room to mount new caps underneath. The new caps are safely enclosed when the cover is put on.

polaraman · #3 10-02-2005, 06:03 PM

SAMS lists a CT232 and a CT235. I did not see a CT234B????? One is SAMS 93 and the other is SAMS 97. I have both. It would be easier to just copy one. Maybe Randy Bassham could offer some input.

pics please!!!

polaraman

Randy Bassham · #4 10-02-2005, 09:19 PM

I'll do some digging, Magnavox used the same basic chassis with minor modifications on a lot of their TV's, for that matter they used similar chassis on their radios too. They used the same basic color chassis from about 1967 through 1972 with modifications. It seems they liked to introduce a chassis and then do improvements on it with each model year rather than a complete redesign. I'd venture a guess that all these sets are similar and maybe based off the CT214.

nasadowsk · #5 10-02-2005, 09:38 PM

Ack! I looked again. The markings are just about rubbed off - it looks like it's 237. Grrr. That's the best I can tell

I'm holding the light at funny angles to see if i can see anything, that's the best I can tell. It's certainly 23something, I can't tell if the last # is a 4 or 7 or what...

The sweep sections seem totaly dead, though the flyback didn't seem blown. Might just be a lot of bad caps, or a bad tube or such. I did get some audio action and that's always a good sign.

As typical, the set needs a new HV suction cup. Man, those things deteriorate....

I'll probbably start tearing into the caps this week or so, at least get what papers I can out of the way.

The horizontal oscilator tube socket is rubber isolated. That's weird. I can't tell just yet what tube the vert osc/output is - probbbly one of the many 6SN7s on the thing (I counted 5) Magnavox must have gotten a deal on that tube, they used it everywhere it seems. There's also an oddball 6SF7 in there. I think that's the audio amp - it's right next to the 6V6 output.

blue_lateral · #6 10-03-2005, 12:49 AM

Dit it really have an hv suction cup? Most of the early b/w stuff I have worked on had the old hook & hang type.

jc

nasadowsk · #7 10-03-2005, 11:35 AM

Oh, this was before everyone cheaped out and used the hook that zaps you as you pull it off. This thing's got a genuine HV suction cup stuck to the CRT. In fact, it seems to be all that holds the HV lead to the darn tube. Oh well. This is the old old type that comes straight out the back of the suction cup, not the more modern one that comes out at a right angle to the CRT.

nasadowsk · #8 10-06-2005, 04:58 PM

Ok guys - it's a CT-237-B. I've got vert, but no horizontal. The flyback looks ok though. I *need* a sams at this point. Anyone got one?

thanks!

polaraman · #9 10-06-2005, 08:56 PM

I dug up my SAMS 82 and 95A today from my storage area. PM me your address and I will drop it in the mail.

polaraman

*Bill Cahill* · #10 10-06-2005, 09:28 PM

Actually, the plug snaps into hole on picture tube. It should be a fairly tight fit. Do you still need a connector? I may have a usable one kicking around I could send you for the cost of the shipping..

e-mail me. [email protected]

nasadowsk · #11 10-06-2005, 11:44 PM

I'll look mine over carefully this weekend if I get a chance. This thing actually suction cups on pretty well, though. I should reform the connector to 'snap' in, too, though. As far as the HV lead and al, I gotta figure out how to pull the HV box out to clean in there - Magnavox was 'clever' with the design and mounted the flyback, power resistors, and 1B3, etc to the box itself, and naturally the riveted everything in place but the flyback.... Well, I guess I'll have to unsolder the power resistor leads - the 1B3 socket and caps and leads are FILTHY, and I'm sure this thing's gonna have some nice arcing when it comes up.