RCA 8-T-244 Table Top TV - Videokarma.org TV - Video

maynardb · #1 09-09-2005, 09:02 PM

I,m new to this forum, so please bare with me. My friend just gave me a 1947? Rca 8-T -244 tv. It has two doors that slide into the cabinet and an 8 inch screen. Whern I tried to power it up, it blew the 5u4ga rectifier tube next to the transformer. I tested all of the other tubes, three are weak ,and I hope to pick up all three plus the 5u4ga tomorrow. Does anybody have info, such as schematics , etc. for this model?
I'm a beginner and I'm flying in the dark on this one. I'd love to get this operational, if possible. Could the caps be causing the rectifier tube to blow? Any advice would be greatly appreciated.
Thanks,

Bruce

Chad Hauris · #2 09-09-2005, 10:56 PM

I would say you are right, there are likely bad electrolytic caps. On something of this age I always replace all of the capsbefore doing further troubleshooting work.
A good test tool is a short checker lamp in these instances when powering up unknown condition equipment....put a 60 watt bulb in series with the power line to the device...if it glows briright and stays bright you have a short and this will protect the device under test from overcurrent.

Working on TV's can be dangerous if proper safety precautions aren't followed...make sure you are familiar with these procedures before commencing repairs.
Check out www.repairfaq.org for good information on TV repair safety.

One test you can do is to hook up your short check lamp to the TV with the rectifier tube out. Check and see if your other tubes light up including the CRT. The test lamp bulb should glow dimly and the tubes should light.

maynardb · #3 09-10-2005, 09:50 PM

Just an update, I got the 5u4 tube at the hamfest and put it in. Presto, chango, it worked! Mind you, there are still some issues, such as the fine tuning adjustment mechanism needs attention. The cloth belt has disintergrated, and the picture isn't the best. Some lines at a 45 degree angle are showing, but damn, it works! Still looking for schematics if anyone might have them.

Thanks,

Maynardb

Sandy G · #4 09-10-2005, 09:57 PM

Still think you oughta take Chad's advice & go thru it & replace the caps...They may be apparently fine , but one could let loose & take out yr CRT..and those are truly made out of what we affectionately call "Unobtainium". In any event, you will prolly never get any measure of reliability or real enjoyment out of the set until you do, I would think. But congrats on saving an old veteran from the jaws of the dumpster !!-Sandy G.

nasadowsk · #5 09-10-2005, 11:07 PM

If the CRT's a 10BP4, they're as common as dirt.

I never understood why, but there are a zillion of those tubes, even NOS, out there. They popup on fleabay all the time, and it seems everyone's got 3 or 4 laying around.

Did RCA expect 10 inch TVs to be the big thing and just make a zillion of them? Was it ever a real popular tube in TVs? I mean, really, there's a LOT out there still.....

bgadow · #6 09-11-2005, 09:11 PM

I would like to have a spare 10BP4 but not enough to ship one. Someday one will turn up locally. I think the reason for their abundance was that nobody really knew what kind of life to expect out of a picture tube so they stocked up. TV repairman & distributors might have thought that they would be replacing lots of these after 6 mos. or a year. Personally I wouldn't worry so much about a bad cap taking out the crt as I would it taking out the power transformer. Now, that you won't find on every streetcorner!

***Eric H*** · #7 09-11-2005, 09:18 PM

I think the 10BP4 is common because it was used in pretty much every 10" set from 1946 to 1950 or so, were talking millions of sets!

Chad Hauris · #8 09-11-2005, 09:20 PM

Also make sure you put a fuse in the power line to the set! (3 amps or so)
Am not sure if this set originally came with one but a lot of the old ones did not.. It will save your power transformer in case there's a short....please replace those caps too as you will run the risk of damage and there's no way you could do a proper troubleshooting job with those old caps.

7"estatdef · #9 09-11-2005, 09:57 PM

Hi Bruce,
Wellcome to the group!!! What you are looking for is a Sam's PhotoFact # 74-8. This will have all the info you'll need to troubleshoot your set. It is circa 1949. You can give findatube.com a try to see if he has it. Nice guy and resonable too.
Terry

It might be 1949 technology but it's good 1949 technology!

kc8adu · #10 09-11-2005, 10:44 PM

would that be that be the findlay hamfest?
i got a admiral 19a11 there .
and now that you know the set can be made to play its time to start recapping!

Quote:

Originally Posted by maynardb

Just an update, I got the 5u4 tube at the hamfest and put it in. Presto, chango, it worked! Mind you, there are still some issues, such as the fine tuning adjustment mechanism needs attention. The cloth belt has disintergrated, and the picture isn't the best. Some lines at a 45 degree angle are showing, but damn, it works! Still looking for schematics if anyone might have them.

Thanks,

Maynardb

Don Lindsly · #11 09-12-2005, 10:56 AM

There are a few of reasons for the abundance of 10BP4s around today. One is that about 98% of all post war 10 inch TVs of the forties used a 10BP4 or the aluminized 10FP4 version. Virtually all manufacturers initially made a 10 inch TV. When shops scrapped trade-in TVs the 10BP4 was one of the salvage parts.

In the late forties conversions were a big business. Customers would have 10 inch TVs converted to 12, 14 and 17 inch screens. It usually involved more than a picture tube, but it usually left a surplus 10BP4. Many of those have survived through the years.

Picture tube re-builders had so many 10BP4s that they stopped taking them back as duds so some shops just left them laying around rather than figure out a method of safe disposal.

As the industry grew, varied screen sizes and TV designs caused the types and sizes of picture tubes to proliferate, so no tube type ever achieved the degree of standardization as the 10BP4.

Don

nasadowsk · #12 09-12-2005, 11:29 AM

Heh. There were really so many 10BP4s at one time rebuilders didn't want them anymore? Hehehehe.

Well, they sure are common. A 21EP4 on the other hand....

andy · #13 09-12-2005, 01:13 PM

...

ohohyodafarted · #14 09-13-2005, 02:39 PM

I was watching that auction. I need a decent 10bp4 for a set I have, but I would rather pay Scotty to rebuild one of my duds thatn pay that kind of money for a used tube. Somebody must have money to burn.

maynardb · #15 09-13-2005, 08:03 PM

Thanks to you all for the great input! I'll take your advice and recap, as soon as I find the schematic for the set, I think someone said that Sam's 74-8 would do , so I'll look for one and recap before firing it up again.

Bruce