Power transformer replacement??

[Tubejunke]

I have mentioned this before but I was a bit unsure. My RCA TCS-127 needs a power transformer. After much hope of this not being the problem I have come to the conclusion that it is. I borrowed a Megohmmeter and verified that my primary is shorted to ground. Along with at least one secondary winding. I stopped checking after that. I dont know how hard this is going to be to tackle. Not doing the work but getting the replacement part or having the existing part repaired.

Are there places that rebuild iron core transformers?

Are there places that sell N.O.S. or replacement transformers?

I have never had to replace any of my transformers so this is new to me. Any help or advice would be greatly appreciated. Here are the part #s on the trans: 970972-1-3
138012

The chassis # is KC534B

THANKS

[Chad Hauris]

I would take the covers off the transformer and make sure the insulation on the hook-up leads isn't disintegrated inside...we have repaired some with bad insulation on the wiring by covering the old wire with heatshrink tubing all the way to the core.

[prewtv]

If the transformer is really bad places like Radio Daze have general replacements
and on Steves site someone rewinds them and with a old sub book maybe a parts set has one like the 9T246 on Ebay for $20.00??
Item number: 150050438486

[Bill Cahill]

Hi. These sets have two line capacitors, and a resistor going to chassis that can fool you. I'd just remove those parts. On secondary, they sometimes had a negative bias supply ending to chassis with a resistor, and a positive secion of an electrolytic on the chassis. You may be actually measuring those two sources.

Bill Cahill

[Tubejunke]

What I did was remove the rectifier. That its self deisconnects 3 leads. Then I removed the two leads going to the small strip with a B+ fuse (I thiink). I removed a lead that goes to one of the filters and I think one that supplies the heater string. I also disconnected the ground side if the line filters. This should have eliminated the short if it were in any of those circuits. I applied AC from the wall and still have a heavy current draw. The transformer hums like it is working its a** off what little time I can leave it on, which is a matter of seconds. The line chord will get hot and there has been a burning smell. I have nearly every indication that the trans is bad.

The megohmmeter does not help as much as I thought. I have compared the readings I get against other sets with known good transformers and they are similar. I was told that I should see no more than around 10M Ohms on the 250v scale and if I saw low readings that would indicate a short. I get nearly the same reading from say either side of the line input to ground. Also I get the same reading from one of the secondary leads going to 5u4 and to ground. The rest seem to be isolated. I will say that the motor tech that loaned me this hand crank megohmmeter is not a television repair man but he is trained decently and spends a lot of time finding shorted field coil windings in electric motors. We thought that a power transformer would not be much different.

Also I have to watch swapping from other sets because I have noticed that even though many RCA chassis use what looks like and many times are the same value components, it is not a given. This ct-127 has a different trans than my 8T-243. Probably the ebay 9T set will have the same one as my 8T. Hopefully something will pop up. On another thread someone said these trans. are pretty common. Hope so!!

[wa2ise]

Originally Posted by Tubejunke

What I did was remove the rectifier. That its self deisconnects 3 leads. Then I removed the two leads going to the small strip with a B+ fuse (I thiink). I removed a lead that goes to one of the filters and I think one that supplies the heater string. I also disconnected the ground side if the line filters. This should have eliminated the short if it were in any of those circuits. I applied AC from the wall and still have a heavy current draw. The transformer hums like it is working its a** off what little time I can leave it on, which is a matter of seconds. The line chord will get hot and there has been a burning smell. I have nearly every indication that the trans is bad.

My next step would be to remove the power transformer from the set (but keep track of what lead went where, especially the primary). Once the transformer is removed, I'd try applying line voltage to the primary briefly again to see if the short is still there. Check the insulation of the wire leads; if it looks brittle and crumbly, the short might be there. Carefully remove the end bell the wire leads come from (if you didn't already do that to remove it from the set) and check further, and slip heat shrink insulation on the problem leads. Of course, if the transformer smells like toast, it might be toast, but don't give up easy on it.

If the transformer in the set is drawing so much current that it makes the line cord get hot, I'd wonder about the circuit breakers or fuses in the house. Check that nobody stuck pennies behind the fuses....

[Bill Cahill]

I totally agree. I also don't see alot of similarity between motors, and transformers. The transformer sounds very shorted, alright, but, I'd agree you should remove it, and physically check the wiring first. If the transformer is making a bad odor, it probably is burned. I'd also suspect something in your house isn't right, as this should trip a breaker, or blow a fuse. The fuse in the tv is only a boost fuse for hv section. You eliminated one possibility by pulling 5U4's. I think this set uses two, but, I could be wrong.

I still say your filters are shot, and reming you there is usually a resistor from line to chassis as well as the grounding capacirots.

By the way, those two line caps were supposed to eliminate line interference, especially from medical devices, which are not even used any more. In most cases, removing them permanently will not affect the performance of the set, and actually, make ths set electrically safer.

Do now, however, attempt this on a ac dc set with out a transformer, as they are a different animal all together.

If the tube line up is the same as yours, chances are a replacement transformer would be fine. Make sure of every wire on both new, and old one. Colors don't always match.

By the way, it might be safer to put a light in series with the primary of the transformer. Under normal circumstances, you'd need a fairly high wattage, but, for this kind of shorts test, 60-100 watt should be plenty. If butl light full blast, no doubt about it, you have a major short. You obviously do, anyway, just, where is it?
It is a fairly common set, so shouldn't be hard to find the correct transformer for. But, consider this.
What is the physical condition of your set?
What type of cabinet does it have?
Are you really in love with the set?
Are you willing to put what ever it takes into bringing the set back to life?

By the way, there is still the resistor network going from B- to the chassis, and will still show a "short".

In all fairness, I love the old sets myself, but, don't destroy a better one for what you have.. It's a nice set, but, RCA used this chassis in many models. By the way, what is the exact chassis no? It would have a KCS in front of it.

KCS stands for Kinescope chassis set.
If anyone is wondering, The CT in RCA's color line stands for Color Television.

Bill Cahill

[Tubejunke]

I'll try to sum up some things that are on other threads and this thread. When I first got the set naturally I used the 100watt bulb to reduce line voltage. Things seemed very hopeful as the bulb dimmed like it should and the tubes all glowed dimly. Perfect. I only did this for like 3 hours. I probably should have done it all night. This set seemed to be in real good shape so I didnt expect to have major trouble. I found that the LV rectifier was open so I replaced that. Then I applied 110V. That is where my troubles began. Instant major transformer hum and WARMING of the line chord, along with the bad smell. I would say that if I had left it plugged in for more than the 5 or so seconds that I did then the breaker would have took over.

At that point I hoped it was bad electrolytics so I went and bought new ones. I really felt good except for the fact that NONE of the existing caps gave ANY indication of anything that would cause a major draw. A cap that bad should be noticable with an analog ohm meter. Needless to say my second thoughts were right. Plugged her in and had exactly the same problem. That leads up to my using the Megohmmeter from work this weekend and pretty much determined that my primary winding is shorted to ground. The needle pegs when you crank the generator. I get the same effect from one of the secondary leads to ground. My wires are in great shape. Sounds pretty shorted. The transformer does not have RCA painted on it like my old 8T-243. Instead the #'s are stamped into the housing. Maybe the factory was trying to save a buck.

As far as the set being worth it. Yes! I have been wanting a roundie with a double d mask for ever. Not a lot around my area. Most people say the first TVs were in town around 1952. Many sets I read about have the 10BP4 like my 8T-243. This set has a larger tube. I forget the exact size. That makes it kind of unique to me. I love the doors as well. I would say the set shows average wear and tear but polishes up very pretty. Also, it has a rebuilt GE crt which is a positive aspect I think. It was installed in the 60's so it may not have much time on it. Such sets pretty much retired through the 70's. Thats how I gained interest as a kid. They were still siting in the corners of local repair shops and easily obtained cheap or free. Some 50's sets were in my high school electronics shop. That was cool. Even a Predicta that I would tinker with. Nobody cared about the older junk. We now had SOLID STATE!!

Hopefully this set will come together well. I want to reduce my collection to some degree and focus on a select few favorites. I really hate getting rid of anything. Y'all know how it is. I still have a late 50's Montgomert Ward's Airline for free if anyone can pick up....

[Bill Cahill]

Hmm. Sounds like it's worth saving. I wonder if this is a 16" set?
I have the power transformer from one of the early 16" sets. It has bad leads,but, I think transformer is still good. Can you get me the chassis no, and a good picture of the back of the set? Thanks. Bill Cahill

[Tubejunke]

Thanks Bill, the chassis # is KCS34B. The c.r.t. is a 12LP4. I don't have a pic of the chassis as we speak but I may get one soon. You seem to be familiar with the old RCA's. Well I'm not as familliar but got some experience working with the "ugly" 8T-243 that I have mentioned and the chassis seem to LOOK identical. Really it LOOKs as if I could trade c.r.t.'s and swap chassis if I wanted to. I suspect there are some component value differences. I really don't want to change the subject to chassis swaps. Right now power supplies are the issue. My 8T had power supply problems as well but they were cured with caps. Not so with this TC-127.

How much difference is the desirablilty in relation to c.r.t. size, if any? It just seems like every other set mentioned has a 10BP4. I know that is a common tube. Again my 12LP4 is a G-E rebuilt with no brightener so I think I am good to go there. I know it would be smart to find out before getting all involved in restoration but unfortunately my tube tester all works fine, exept the c.r.t. test. It used to work fine and suddenly stopped. Sometimes I think it is crazy to use diagnostic equipment that may need as much diagnosis as the repair job......

[Chimes]

Originally Posted by Tubejunke

The megohmmeter does not help as much as I thought. I have compared the readings I get against other sets with known good transformers and they are similar. I was told that I should see no more than around 10M Ohms on the 250v scale and if I saw low readings that would indicate a short.

I not sure just how much voltage the megohm-meter is putting on the wiring. Are you sure it isn't more than the insulation can take?

If you have a short that is causing the transformer to pull enough current to cause the line cord to heat up you should be able to measure that easily with a standard ohm-meter.

This may give you and idea of what you should see on the different windings resistance wise: http://www.radioremembered.org/xfmr.htm

[blue_lateral]

Glad you're gonna save it. An early RCA with a newer CRT is a recipe for an excellent picture.

Please try what the others suggested and disconnect it. Test it on the bench. The forums over on antiqueradios.com are full of old threads where someone was convinced the transformer was shorted, and the problem disappeared when the transformer was totally disconnected. Shorted tube sockets, dial lamp sockets, and such. I'll admit what you said sounds really bad for the transformer, but humor us and try it. If it's bad, it's gotta come out anyway.

Even if it's bad you still might fix it by replacing the insulation under the end bells like Chad suggested.

I don't have a crank megger. I use a HV power supply and a VTVM. You don't happen to have these two items, do you? I suspect this is doing exactly the same thing as your megger anyway. If you have this stuff laying around, post back, I'll tell you how.

Ok, if it *is* toast, I don't know of anyone rewinding, but I've heard Heyboer will make you new transformers to original size and specs. This might be a good option if a universal one wont do for some reason, or you want an exact fit.

Good luck,

John

[Bill Cahill]

The good news is I have a KCS 34B. The bad news is I might need it's transformer. I picked up a T-120 that someone has messed up the power suppyly, replaced power transformer with possibly the wrong one, then, wired it wrong.I still have to check. However, I do have an extra one with bad wires,that I believe is not toast. It's a commontrhasformer in RCA's, and was used on a number of chassis'. Voltages, approx., follow:

Pri. 117volts ac. 50-60hz. Hv. Winding. 730volts AC Center tapped.
Sec.2 5volts AC 4 A.
Sec. 3 6.3 AC. I belive that one is 11A.
Sec. 4. 6.3 AC 2A insulated for 1200 volts. This fil. alone is used for the 6W4 fil. , which is not grounded, as it is connected to cathode to cut back on danger of arcing. Never ground this, or connect it with other filaments, as I guarantee it WILL cause major dammage.

If I am wrong about that winding, and your damper tube just happens to be a 5V4 The fil. specs follows: 5.0volts, 3A. Insulated for 1200 volts. On our inflated ac voltage of 120-124volts ac, The voltages will be somewhat higher.

I hope this helps.
Bill Cahill

[bgadow]

Originally Posted by Tubejunke

How much difference is the desirablilty in relation to c.r.t. size, if any? It just seems like every other set mentioned has a 10BP4. I know that is a common tube. Again my 12LP4 is a G-E rebuilt with no brightener so I think I am good to go there. I know it would be smart to find out before getting all involved in restoration but unfortunately my tube tester all works fine, exept the c.r.t. test. It used to work fine and suddenly stopped. Sometimes I think it is crazy to use diagnostic equipment that may need as much diagnosis as the repair job......

Generally with early sets the smaller the screen size the more desirable the set. 12" isn't far from the standard 10" and is still very desirable. Really, any round tube sets are. When you start getting into rectangular tubes the interest starts to fade.

[Tubejunke]

To Chimes, I'm not sure how much voltage the megohmmeter puts out either. The guy that loaned it to me said something about 4 times the operating voltage. He could have meant that the meter puts out 4x or that is what I needed. There were three ranges, 200v, 600v, and 1000v. I used the 200v. I seriously doubt that the momentary spike would damage anything. Nothing got hot. Also thanks for the link! Everyone should be able to use that info. I find the color coding confusing as my transformer does not seem to follow suit with what they show.

To Bill, no I don't have the items you mentioned. However I feel like simple resistance readings should tell the tale of a major short like I have. I should not have resistance readings from disconnected wires to ground in places I am getting them. A few minutes ago I took some readings. Here are some examples. These checks are to ground. Pin 4/5U4=1,300 ohms, pin 6=1294 ohms, the lead that goes to the switch has 91,000 ohms. I get 1.8 ohms across the ac line with the filters disconnected. Thanks Bill!!

To Bryan, I kind of knew round was better but I wasnt sure about size. I know any of us would like to have one of those huge DuMont Royal Sovereign sets with some ridiculously large crt, so I guess size is not necessarily a rule of thumb. Also I have a couple of the 50s rectangulars that I know are good finds. I always thought that interest started falling off around the early 60s with old TVs. The early Color sets then take over. There really are no guidelines as the hobby has expanded somewhat and there are some who find 70's stuff interesting. Some of this is relative to a persons age if you think about it. One day someone may find nostalgia in the plastic junk Walmart calls TV's. Go figure!!

Thanks for the help everyone. Still open to ideas and suggestions....