Hi everyone,

I bought my first project TV, a Magnavox 10T338N from 1965 I believe. The picture tube it marked 75E, 23MP4, 836, date code 520. At the seller's house, the set had audio but no video. After the ride home, the audio disappeared too.

Where can I obtain a schematic for this set? I couldn't find anything through google. Any advice is appreciated!

Thanks,

Ryan M. Landry

Neat set !

I did try to look up that number, no luck...
You should be able to get a Howard Sams Photofact/schematic for this set. What is your model number and chassis number? Anyone with an index book or visiting the Howard Sams website can provide you with the Photofact number. Once you know that, many folks (and AK'ers) may help you to obtain one. Also, if you have a county library they should have a technical section loaded with photofacts too that you can copy from.
A thing to remember about Magnavoxes and numbers....The cabinet itself may have it's own number but it is just about useless to obtaining schematic info. And that number may or may not necessarly be the "model" number! If indeed it is used as a model number, all the better. Plus, that chassis was used in many models/cabinets so a chassis number should always be valid.
So, all that being said, you may be looking at two, or three numbers to dissect from and go from there. Keep us posted!

Great lookin set. Don't fire it up until you replace the power supply capacitors at the very least. 40+ year old parts do not belong in there. :no:

Hey Ryan,

Cool set, I wouldn't mind having one of those myself.

Search for this thread "Beginners guide to Vintage TV Restoration?" on AK it has alot of good info to get you started, that is if your a novice like myself. I've got two under my belt and a third one started. I could have never pulled it off without these guys.

Good Luck and have fun.

Chris

Thanks y'all. I'll look for that beginners' guide. I'm going to dig into the set this weekend or next week and try to find a chassis number.

I never seem to have very good luck on using the search engine on AK. What is the secret for using more than one word? I can narrow things down by searching in just the tv sections. But I still get tons of post that are non relevant.

Here's the link to the beginners guide.



http://www.audiokarma.org/forums/showthread.php?t=145086

Hi again,

I unbolted the chassis this evening and looked everywhere, but could not find anything that was obviously a chassis number. This is what I did find:

stamped in metal chassis: 730450-2
written on HV cage: 14/14/14/93
on tube layout sticker: EL 2072-1
on circuit boards: 210169-6, 210165-8
model no. on cabinet: 10T338N

I'm at a loss - I would really like to have a schematic but none of the numbers I found cross to a chassis number in the SAMS index. The only thing I found close was a listing for a chassis CT338 (series 105), but I'm not sure that's even a TV. If anybody has any suggestions, I could sure use them.

Thanks,

Ryan

Usually there is a sticker or marking on those magnavoxs that you wouldnt think is the chassis number . I had the same problem with mine before i finally found the chassis number and was able to obtain a sams . You should go ahead and replace those electrolytics and check all tubes , then that set just might fire up. Those orange drop caps and red mallorys were pretty reliable . Thats just my opinion becuase i did a few of these magnavoxs . THEY are one of my favorites .

Check SAMS 736, folder 3 - same boards and tube complement as your set, albeit in a portable. The RCA CTC-16 roundie is in the same SAMS, so it's a popular SAMS...

Cheers,

Found it! The actual SAMS is 779, folder 2 - matches your chassis exatly. You have a U44 chassis - yours may be late production, as the flyback part number in SAMS shows a -1, and yours is clearly marked -2.

Magnavox used some crappy tube sockets, so watch out for them.

Hope this helps -

Cheers,

Found it! The actual SAMS is 779, folder 2 - matches your chassis exatly. You have a U44 chassis - yours may be late production, as the flyback part number in SAMS shows a -1, and yours is clearly marked -2.

Magnavox used some crappy tube sockets, so watch out for them.



Thanks so much Brian! I am extremely grateful to you!

Hello everyone,

I obtained a Sams for the set and dropped the chassis last night. Everything looked pretty clean except for two areas:

Someone did work to the horizontal AFC network, which is one of those all-in-one pc chips that look like a wide orange-drop cap with 5 leads (forgive me - I don't know the proper name for these.) They must have used a pretty hot iron, as heat blackened the board and cooked the insulation on a couple of wires. My question is: is there a good source for these chips, or are they made of unobtanium? Also, was there a reason other than convenience that the resistors and caps were integrated into the single chip?

Ryan

Hi everyone,

I'm about to finish re-capping this set (Magnavox U44) but have a question:

I was able to get a picture on the set, but it is very dim - only viewable in a dark room with the brightness almost fully up. When I pot the brightness all the way, the picture goes "negative" - like looking at a photo negative.

Any advice for me? Maybe some circuit in particular to double-check? Unfortunately, I don't have a CRT tester, I have a gut feeling the crt is bad, but am trying to eliminate any other possibilities for this condition.

Also, where could I find information on which tubes are compatible with a 23MP4, in case I have to start searching for one?

Thanks,

Ryan

Classic symptoms of a bad tube, I think your gut is telling you true.

I seen that tube listed in the classified on ETF . You might want to look there. There was a guy selling a bunch of crts and that was one of them . I think you should be able to locate one .

There's a seller that lists a 23ALP4 on ETF. That looks like it should work. The 23MP4 is listed as a replacement for it.

John

Thanks folks!

I saw the 23ALP4 but wasn't sure it would work.

Is there a standard reference for CRTs showing specs & interchangeability?

That Magnavox is really a beautiful television.

While I was looking at the picture of this set, I could not avoid some thinking to come to my mind: we, the TV collector guys, we are really a very unusual brand of people, aren't we? I take myself as an example. The vast majority of people care nothing about those old TV sets, but me... well, I came to the conclusion that at this point in my life, there's only one thing that makes me feel more enthusiastic about than a nice and rare vintage television set, and that only thing are pretty ladies.

When I am hunting for vintage televisions, it seems like an adventure to me, I go to some very odd places for finding some sets. I almost feel like I were some sort of Indiana Jones, no kidding, because I believe that collecting those old devices is somewhat akin to archeology. I really feel that way, that we are doing a kind of archeological job on finding, rescuing and collecting these TVs. If it were not for people like us, most likely in 50 years from now the only way the people of the future could see a TV set from 1950 would be by looking at photographs.

Have you checked the obvious? B+, HV, and the CRT voltages? If all are within the range of those printed in the Sams, yes, you may have a bum CRT. I've seen CRTs with open cathodes give the same symptoms, but it's best to rule out all other factors first.

Cheers,

I don't know if there's a standard reference. In the Sylvania CRT Technical Manual they list the 23MP4 as a replacement for the 23ALP4. They don't list a replacement for the 23MP4, but I assume it would work the other way. I don't see any differences other than the hearter current.

John

Thanks folks!

I saw the 23ALP4 but wasn't sure it would work.

Is there a standard reference for CRTs showing specs & interchangeability?

Have you checked the obvious? B+, HV, and the CRT voltages? If all are within the range of those printed in the Sams, yes, you may have a bum CRT. I've seen CRTs with open cathodes give the same symptoms, but it's best to rule out all other factors first.


I need to find an HV probe - I haven't had any luck turning one up locally. I am getting HV, but how much I don't know.

That Magnavox is really a beautiful television.

While I was looking at the picture of this set, I could not avoid some thinking to come to my mind: we, the TV collector guys, we are really a very unusual brand of people, aren't we?


Yeah, I think you're right :D When I ask about old TVs or radios at garage sales, I'm usually directed towards something from about 1990.


there's only one thing that makes me feel more enthusiastic about than a nice and rare vintage television set, and that only thing are pretty ladies.


I'm married now, but it was certainly a lot easier finding pretty girls than vintage electronics!


When I am hunting for vintage televisions, it seems like an adventure to me, I go to some very odd places for finding some sets.

I stopped to look at a house for sale last week, looks like someone walked away from it 10 years ago. There is a c.1980 Quasar console in the living room - was thinking about calling the realtor to see what else was in there.

Have you checked the obvious? B+, HV, and the CRT voltages? If all are within the range of those printed in the Sams, yes, you may have a bum CRT. I've seen CRTs with open cathodes give the same symptoms, but it's best to rule out all other factors first.


My voltages at the CRT are fine, B+ in some places is up to 20% off - I'm waiting for some electrolytics to come in to finish replacing the metal cans.
I do not have a way to test HV - I am getting HV but can not measure it.
I have replaced the HV rectifier, HO and damper tubes.

The pics below were taken in a dark room. Until I can find a CRT tester and/or an HV probe, does anyone have any suggestions of things I can check in the meantime?

Have you tried hitting it with a CRT rejuvenator on the lowest setting? On a tube that far gone, I don't think you'd be hurting anything by trying it.
Some B&K CRT testers/Rejuvenators also have a "remove shorts" setting that is the same as a rejuvenation setting, only not as hard on the tube. If anything, rejuvenating the tube would get you a few more months of an acceptable picture while you look for a replacement tube.

I haven't been able to find a CRT tester/rejuvenator locally - excepting a fairly new Sencore for $500, which is outside of my budget. I guess I'll start saving some dough for one from the auction site.