Hello,

I have a WM203HWD4 with a bad flyback transformer. Does anyone know if a Thordarson FLY 641 will fit? I see it is listed as an equivalent to the original GE part (EP77X10), but wonder if it will fit properly mechanical-wise.

Also, can anyone advise any sources for flyback transformers for this set?

Thanks!




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Hello,

I have a WM203HWD4 with a bad flyback transformer. Does anyone know if a Thordarson FLY 641 will fit? I see it is listed as an equivalent to the original GE part (EP77X10), but wonder if it will fit properly mechanical-wise.

Also, can anyone advise any sources for flyback transformers for this set?

Thanks!




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I have a good used one, from a scrap older model set. An EP77X3. Unless this one crosses over to the Thordarson number, it probably won't work.
The set that this one's from, uses a 12GE5 horiz output. The newer P/C's used a 12JF5 tube. It might've been good for more high voltage and the impedance might be different.

I think you're right -- the EP77X3 is not listed in the SAMS book for my set (H4 chassis). It lists EP77X10, or EP77X4 AND EP12X84 (if I'm interpreting that correctly).

Going from memory, I'm pretty sure my set uses the 12JF5 horizontal output tube.

There is no Thordarson or Stancor equivalent listed in the SAMS for the flyback, yet the Thordarson FLY 641 box states its an exact replacement. Perhaps Thordarson developed this after the SAMS book was published? The box also states its an improved design.

Thanks!

I think you're right -- the EP77X3 is not listed in the SAMS book for my set (H4 chassis). It lists EP77X10, or EP77X4 AND EP12X84 (if I'm interpreting that correctly).

Going from memory, I'm pretty sure my set uses the 12JF5 horizontal output tube.

There is no Thordarson or Stancor equivalent listed in the SAMS for the flyback, yet the Thordarson FLY 641 box states its an exact replacement. Perhaps Thordarson developed this after the SAMS book was published? The box also states its an improved design.

Thanks!
I used all Thordarsons, for the RCA replacements. They definitely were an improved design. A potted silicone HV winding, vs , the wax and rubber RCA design. Also, an improvement over the GE issue. :yes:

Lots of numbers floating around. Not sure about the
portacolor flys but many GE FBT's from that era sold
HV winding, pulse winding & core halves separate. It
can cause some confusion......
Dont know how Thordarson, Stancore etc sold them.
Changed few GE FBT's, they went to the dump at that
point.

73 Zeno:smoke:

A few years ago I changed the flyback in the newer of my Portacolors, I think with the HE chassis (?) Used a Thordarson that I bought from Moyers, maybe they have more? Worked well.

before replacing a flyback it would need to be determined that was the problem.

A plate drive signal from a tester like a BK 1076 would be a good start.

Without that I would look for a flyback ringer

also you should make sure the Boost filter cap is ok. I cant recall but I think it is a .1 hard shelled tube cap. if you get a pic with the set back off I could take a closer look.

Let me provide some more background on the situation. The original problem was loss of picture (still has sound). Because I don't have the training & specialized equipment for television repair, I found a local shop which does vintage electronics restoration exclusively, and took my TV there. They told me that they replaced some capacitors and one of the HV tubes (forget if it was the horizontal output or HV rectifier), and the set was able to maintain high voltage for ~20 minutes, but then the flyback failed. I don't know if a ring test was done or just how this was diagnosed. They still have the set, as I've been trying to help source a new transformer. So I can't take photos of it at the moment.

Thank you to everyone. I appreciate your help & input.

I know there are varied opinions of the PortaColor, but I'm motivated to keep this particular one working, for sentimental reasons.

I'm proficient with electronics, but tubes are a little before my time, and I lack expertise with television circuits (particularly the HV portion). I know what I don't know, and won't just haphazardly & aimlessly start messing with things. I want to learn as much as I can, however.

Let me provide some more background on the situation. The original problem was loss of picture (still has sound). Because I don't have the training & specialized equipment for television repair, I found a local shop which does vintage electronics restoration exclusively, and took my TV there. They told me that they replaced some capacitors and one of the HV tubes (forget if it was the horizontal output or HV rectifier), and the set was able to maintain high voltage for ~20 minutes, but then the flyback failed. I don't know if a ring test was done or just how this was diagnosed. They still have the set, as I've been trying to help source a new transformer. So I can't take photos of it at the moment.

Thank you to everyone. I appreciate your help & input.

I know there are varied opinions of the PortaColor, but I'm motivated to keep this particular one working, for sentimental reasons.

I'm proficient with electronics, but tubes are a little before my time, and I lack expertise with television circuits (particularly the HV portion). I know what I don't know, and won't just haphazardly & aimlessly start messing with things. I want to learn as much as I can, however.
If the set was mine, I would try to source a replacement transformer. If Thordarson made a replacement transformer, it could have been a high failure item. Try to contact Moyer's and see if they still have one.
I looked at my earlier model Porta-Color and it uses the EP77X10 transformer. This set uses the 11WP22, low focus voltage CRT and the 12JF5 horizontal output tube. I finally finished the repairs on the set and will be part of my collection. :thmbsp:

prob just my natural instinct not to go with "bad flyback" as am concerned this could just be a way to pass off on trying to fix a tough dog.

As long as the shop is reputable and used to working on vintage stuff then I assume they are correct in deciding the fly is bad. For me I would not assume that unless it literally burned to a crisp (fire or smoke seen coming from the fly), and perhaps that is what happened after the 20 min of run time. I have seen some really nasty looking flys that work perfectly fine so it can't be just a visual inspection/pronouncement.

If it simply ceased to produce HV and there was no smoke/fire, then I would prop try the TV analyst plate drive signal, that is a pretty fool proof test.

Just would hate to see a lot of effort put into finding a replacement, installing it and it still not work. I had the same thing on a recent predicta that the owner stated "bad flyback", which turned out not to be the case but was rather a shorted boost cap. The owner had sold it at a swap meet after a fruitless attempt to find a predicta flyback (pretty rare items). I have worked on only 3 predictas, all had nasty looking flybacks, all did not produce HV, all ended up not needing flys to get working again.

Lastly I have seen a video of someone that took a bad fly (in this case the HV tire would smoke, but the primary checked out at least for resistance) removed the old wax, dug out the carbonized paper where the HV short took place and rewaxed it using molten wax and a vacuum to draw the wax in. After the process was complete the fly was reinstalled and worked fine.

Not recommending this if you can source one, but just something to keep in mind (do not throw away the old one if you do get a replacement).

I hope you get it working they are fun little sets.

Not implying for a minute that the shop isn't reputable, but I know for a fact that in the old days there were shops that would stick a pin in the flyback to get it smoking, in order to bail on a repair.

Even with a reputable repairer, but there is sometimes a tendency to find the most expensive part faulty without adequately checking passive components. I have definitely done that. A shop of any kind probably would not be up for repotting a fly, either, that would be up to you.

Even with a reputable repairer, but there is sometimes a tendency to find the most expensive part faulty without adequately checking passive components. I have definitely done that. A shop of any kind probably would not be up for repotting a fly, either, that would be up to you.

Another stroll down memory lane!
I first started repairing TV's, for friends and neighbors, in my early teens. If the set didn't produce high voltage and if it wasn't a tube, I would the blame the flyback. It seldom was the problem. :sigh:
That was like, 55 years ago. Learned a little bit, since then. :D

Dave,

Is the boost filter cap the long, narrow one that is in the back corner near the HV cage? I seem to recall it had (4) terminals, but could be mis-remembering.

if you can get a pic of the back I can prob ID it for you.

should be a .1 rather large tubular cap in a hard white cermic tube shell. should say 1000vdc.

the locations I have seen it in are the very back of the chassis pcb near the damper tube OR mounted up off the pcb on under what I think is a choke coil (looks like a transformer) this is part of the tuner/fly/power supply section. there is also a .01 on the schematic from the boost term to ground, but IIRC that is a disk and not likely to be a problem mounted right on the back of the flyback directly to the pins.

http://www.youtube.com/watch?v=6nTiAH7i0lY

go to 1:10 seconds

that is one place they have them

Dave,

Yes, what I was envisioning is not on the main/chassis PCB, but up under the choke coil. Under the area where the power cord and ANT. terminals are located. I still don't have the set in my possession, but should take detailed pictures when I do.

I would def look to replace that one, be sure to use at least a 1kv (not the 630's that are commonly sold). I have had some of those cap fail, but not all of them. Its not to hard to replace so with out some other diagnostic tools its a good guess. You cant really test them as most CAP testers max out at 450-500vdc leak voltage. there is also a verticle .047 cap on the back of the pcb, also a white ceramic tube cap. I think its just a B+ RF filter cap and as such unlikely to be killing HV (unless the B+ is low to to leakage from it, but I doubt it), but it prob would not hurt to replace it as well since its just a paper cap inside.

I have a general question about the flyback. I'm reading the SAMS Photofacts for my set (folder 1223), it lists what appear to be a couple different variations for the part that was used for the flyback. One item listed is "core half." What is the core half? I've heard it referred to as a separate "donut" that comes off, but I'm not picturing what part this would be. Can anyone explain this?

I believe that the actual coil could be removed (with some work) from the frame. Probably have to undo all the leads and I believe there is a metal clip that holds the framework together. I had some pieces of the frame (maybe wrong terminology) for a GE flyback, NOS. Not real sure why they'd bother to sell it that way. I know GE flybacks were famous for being noisy (high pitched squeal) and I'm thinking that type of construction would be the reason why. Best to replace the whole thing. If you can get the improved Thordarson type, do it.

I have a general question about the flyback. I'm reading the SAMS Photofacts for my set (folder 1223), it lists what appear to be a couple different variations for the part that was used for the flyback. One item listed is "core half." What is the core half? I've heard it referred to as a separate "donut" that comes off, but I'm not picturing what part this would be. Can anyone explain this?
The OEM FBT comes in 3 parts. HV winding, pulse winding
& ferrite core halves with spacers & U shaped mounting. If
you use the OEM you should get a new core. Its common to
crack & you need the spacers or it will sing. Also the metal is
cheap & it can break tightening the nuts. GE is the only one I
remember doing it this way & have no idea why. But there
tint control was backwards from everyone else for years. On
my GE oven the temp up & down are opposite from convention.
Go figure..........

73 Zeno:smoke:

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