Dove right in! Help with RCA 21-D-8628

Greetings!

First time poster, and perhaps new obsession with this tank of a television.

I have some experience with antique and vintage telephones, cameras, and a few Edison cylinder phonographs. Television is something that I never really expected to get into, least of all a 1957 RCA corner console 21" black and white tv.

I am learning as I go and while I have learned a great deal, I am just beginning to understand this albatross on my hands.

I will link to some of the pictures that I have posted in other forums looking for help.

Basically...I need to rebuild or find a compatible transformer. Each time I read the schematics for the chassis, I see any number of voltages coming and going to the various components. The transformer is burned up, it would last long enough to start smoking while the tubes warmed up. No surprise why the cord was cut!

I am hell bent to either resurrect this beast, even if I have to (heaven forbid) replace the kinescope with a square ish flat screen and keep the panoramic sound speakers. They sound great of course, RCA.

I have started removing components from the chassis. The old solder is being a real pain in the antenna to remove. I prefer to re-wire, solder, cap, etc., the entire piece. You can see many repairs over the years and some badly laid wire that should be harnessed, or just create a more compacted version of wiring.

I have the field service data booklet that lays everything out, that is a big help. But I am still learning to read it.

Any help would be appreciated! Ask questions and find out quickly what I don't know! I don't mind, just don't tell me to give up; that is something I no longer consider much in my life.

https://imgur.com/gallery/PQzX4jL
https://imgur.com/gallery/VsCpGws
https://imgur.com/gallery/0lauJxJ
https://imgur.com/gallery/Sl7MG5u
https://imgur.com/gallery/rz2qNDr

[old_tv_nut]

Originally Posted by BandDirector

Greetings!

...some badly laid wire that should be harnessed, or just create a more compacted version of wiring.

Caution! Some minor issues can be caused by bundling wires or making them "neat" when the factory did not build them that way. Sweep currents of multiple amperes live with signal currents of millivolts in a TV, and moving wires from their original dress can induce sweep interference into the picture.

As an example, when I worked at Motorola, the assembly line for a given chassis had an approved sample locked in a clear plastic case, and the assemblers were told to duplicate the physical placement of all components and wires. Any question of doing it differently was run past engineering, who would change the sample and write an accompanying official change notice.

[JohnCT]

You should be able to find a transformer for that unit. Make sure you don't run a new one until you monitor the current from the 5U4 output.

Most TVs of that era used very similar transformers. If you can't find one, one from a junk chassis can be made to work without too much effort. Make sure the one you're subbing has sufficient filament current capability, or you can add a filament transformer in place of the original filament winding. You may have to add a dropping resistor if a replacement transformer has too much B+.

In any case, that's a very unique and handsome console in an era where they often weren't.

Oh, and welcome to Videokarma.

John

[old_coot88]

Others' opinions may vary, but here's my $.02 worth..

1. Service-wise, those early printed circuit layouts were the worst ever conceived, with the foil side of the boards made inaccessable (what were they smokin' to come up with that idea? Musta thought the design was bulletproof and would never need troubleshooting.

2. The newly-introduced small neck CRTs usually died an early death. Before proceeding any further, find someone with a CRT tester to verify that (if by some miracle) the CRT is good.

[Tim]

Good luck with your project. As has been mentioned, there are no points given for "neatness" in the wiring. The factory wiring layout and placement is important for the best performance. This includes which wires are against the chassis and which ones are not.

Your chassis is covered in Sams Photofact #400 folder 4. That gives the voltage and current specs for the power transformer. There is no Merit Sub listed but the Thordarson Catalog lists their 26R127 as a substitute for the RCA part number.

[JohnCT]

Originally Posted by old_coot88

Others' opinions may vary, but here's my $.02 worth..

1. Service-wise, those early printed circuit layouts were the worst ever conceived, with the foil side of the boards made inaccessable (what were they smokin' to come up with that idea? Musta thought the design was bulletproof and would never need troubleshooting.

True. Don't have a clue what they were thinking other than having exceptional built-in shielding. I worked on a few when I was a young shaver, and my dad had me tack in the defective part on top of the board. Once the TV was running, he had me remove the circuit board and place the components as the factory did.

One good thing about it was that you had to use more technique than just shotgunning if you wanted a nice neat job. Later on, when RCA went to their "unitized" chassis (no more modules), the technique as described in the service manuals was to cut the defective part off the top of the board and solder a new one in place using the old leads. The reason is that RCA used a conformal coating on the bottom they did not want to be disturbed. I used to install those parts through the board despite RCA's admonition not to.

Originally Posted by old_coot88

2. The newly-introduced small neck CRTs usually died an early death. Before proceeding any further, find someone with a CRT tester to verify that (if by some miracle) the CRT is good.

Another good point that I totally missed.

John

[fixmeplease]

I have a post somewhere on here when I did my 1958 corner tv. It was my 2nd or 3rd tv I did. Took me 2 years to find a good crt close to me (I live in the sticks and didnt want to drive 100 miles), but it now makes a really nice picture and the sound is incredible. I watch westerns on it because of the rounded screen, great sound where I hear every horse sound clearly and love it.

Mine has a hot chassis but I might have the transformer you need here and will look the next day or two on a spare chassis I have that came with the good crt I bought.

I did the cut loop and crimp??? technique on a crapload of parts on the circuit boards. It took a lot of time but was a great learning experience but yes frustrating at times. Dont let it scare you. Yes, they are harder to work on than others for sure.

[JohnCT]

Originally Posted by fixmeplease

I did the cut loop and crimp??? technique on a crapload of parts on the circuit boards.

Loop and crimp is fine as long as it's done quickly so as not to partially melt the solder on the bottom of the board a bit. In fact, loop and crimp is overkill for durability.

Years ago I helped a guy work on an old tube guitar amp, and the sockets were brittle. Rather than risking having the metal terminal break flush at the tube socket, I cut a paper cap off the tube socket about half an inch away from the socket and laid the new part *right along side*, so they overlapped that half an inch, then soldered then together.

The guy howled a bit until I explained that parts contained on circuit boards are *only* attached by solder, and not nearly as much solder as the overlapped part had. He saw the light.

John

Originally Posted by fixmeplease

I have a post somewhere on here when I did my 1958 corner tv. It was my 2nd or 3rd tv I did. Took me 2 years to find a good crt close to me (I live in the sticks and didnt want to drive 100 miles), but it now makes a really nice picture and the sound is incredible. I watch westerns on it because of the rounded screen, great sound where I hear every horse sound clearly and love it.

Mine has a hot chassis but I might have the transformer you need here and will look the next day or two on a spare chassis I have that came with the good crt I bought.

I did the cut loop and crimp??? technique on a crapload of parts on the circuit boards. It took a lot of time but was a great learning experience but yes frustrating at times. Dont let it scare you. Yes, they are harder to work on than others for sure.

I don't know what the cut, loop, and crimp technique is; can you elaborate?

As to the transformer, that would be tremendous! I was thinking about rebuilding it; and, it may be worth it in the end just for the experience. I don't expect it to work once I am done with it...and since I cracked the original shell I'll have to have it machined somewhere. Not impossible.

I love the speakers, I attached my GE stereo to it and it was probably a bit overloaded on those RCA speakers, but the clarity is incredible. I'm tempted to just leave it connected to some L/C/R leads just to have Panoramic monaural sound coming from my stereo.

Originally Posted by old_tv_nut

Caution! Some minor issues can be caused by bundling wires or making them "neat" when the factory did not build them that way. Sweep currents of multiple amperes live with signal currents of millivolts in a TV, and moving wires from their original dress can induce sweep interference into the picture.

As an example, when I worked at Motorola, the assembly line for a given chassis had an approved sample locked in a clear plastic case, and the assemblers were told to duplicate the physical placement of all components and wires. Any question of doing it differently was run past engineering, who would change the sample and write an accompanying official change notice.

I have plenty of pictures of the original wiring, so I will just follow those as guides. Thanks for the heads up!

Originally Posted by old_coot88

Others' opinions may vary, but here's my $.02 worth..

1. Service-wise, those early printed circuit layouts were the worst ever conceived, with the foil side of the boards made inaccessable (what were they smokin' to come up with that idea? Musta thought the design was bulletproof and would never need troubleshooting.

2. The newly-introduced small neck CRTs usually died an early death. Before proceeding any further, find someone with a CRT tester to verify that (if by some miracle) the CRT is good.

As to number 2: I purchased an old CRT tester for Color/B&W from eBay. When I run 6.3 volts to the tube heaters I see a near 80% for cathode grid and cathode; if I switch it from quality to leak I don't see the indicator glow for a leak for the cathode. I'm assuming 6.3 volts is the correct test voltage, and it seems that the transformer has a 6.3 volt lead.

[Electronic M]

On sets where the IF stages are hand wired disturbing the lead dress can ruin the alignment which is not something you want to mess up.

It might be a good idea to find a 5 tube AM radio and make that your first project. The average monochrome TV is 5x as complex as an AM radio but uses similar parts so if you make a mistake Tracing it down from the schematic is much less difficult.

Phill's old radios on the internet has a lot of good beginner info and detailed write ups with pictures of TV and radio restorations he has done.

The original trans is probably shot, but it might not be. If the B+ line in that set has a hard short on it (say from a shorted original lytic cap) and you didn't pull out the 5U4 before power up the trans could just be complaining of the overload.... sometimes if you overload a transformer till it smokes but don't run it too long it will survive, but the odds of that are not high.

Good luck on your project.

Originally Posted by JohnCT

You should be able to find a transformer for that unit. Make sure you don't run a new one until you monitor the current from the 5U4 output.

Most TVs of that era used very similar transformers. If you can't find one, one from a junk chassis can be made to work without too much effort. Make sure the one you're subbing has sufficient filament current capability, or you can add a filament transformer in place of the original filament winding. You may have to add a dropping resistor if a replacement transformer has too much B+.

In any case, that's a very unique and handsome console in an era where they often weren't.

Oh, and welcome to Videokarma.

John

Thanks for the welcome!

It is a very unique and handsome tv, I'm hellbent on restoring it so that I can use it the way it deserves.

What is B+, and, what do I need to worry about?

Originally Posted by Electronic M

On sets where the IF stages are hand wired disturbing the lead dress can ruin the alignment which is not something you want to mess up.

It might be a good idea to find a 5 tube AM radio and make that your first project. The average monochrome TV is 5x as complex as an AM radio but uses similar parts so if you make a mistake Tracing it down from the schematic is much less difficult.

Phill's old radios on the internet has a lot of good beginner info and detailed write ups with pictures of TV and radio restorations he has done.

The original trans is probably shot, but it might not be. If the B+ line in that set has a hard short on it (say from a shorted original lytic cap) and you didn't pull out the 5U4 before power up the trans could just be complaining of the overload.... sometimes if you overload a transformer till it smokes but don't run it too long it will survive, but the odds of that are not high.

Good luck on your project.

Thanks! I think the transformer itself is shot, the inside (if you look at some of the links above you can see it) has burned more often than just my testing it about 5 times.

[Electronic M]

I've seen some scary crispy stuff work like new and I've seen some like new stuff DOA. Electricity doesn't care how ugly the path it takes is.

I would try powering the transformer without a load on it and if it don't smoke measure the secondaries (be careful* the plate winding has potentialy leathal voltage and current on it).

* Keep one hand in your back pocket and work on insulated surfaces.