RCA 21CT55 #8802897 is Dead

[John Folsom]

Yeah, but the way I read it, I think that is what he was measuring. I could be wrong.

[Tomcomm]

The first replier to my thread seems to consider himself the VK Safety Nanny and member attack Pit Bull. Has he considered getting professional help with his obvious anger management problem? Just my opinion..............

That said, my normal +425v current of 265ma is always measured across the HV cage fuse clips. RCA requires a 300ma fuse so the flyback is well protected. I usually use a 500ma fuse since I couldn’t find a 300ma item but accidentally used a 1amp fuse when the flyback cooked so it didn’t blow. This wouldn’t make any difference since the flyback shorted and was doomed.

My only “experiment” with the CTC2B’s power supply was the replacement of the big selenium rectifiers with small silicon power diodes. This simple and logical change raised the B++ from 392v to 425v or 8.4%, well within RCA’s safety margin. How many members performed this same “experiment” on their sets??

[kx250rider]

Originally Posted by Tomcomm

The first replier to my thread seems to considers himself the VK Safety Nanny and member attack Pit Bull. Has he considered getting professional help with his obvious anger management problem? Just my opinion..............

That said, my normal +425v current of 265ma is always measured across the HV cage fuse clips. RCA requires a 300ma fuse so the flyback is well protected. I usually use a 500ma fuse since I couldn’t find a 300ma item but accidentally used a 1amp fuse when the flyback cooked so it didn’t blow. This wouldn’t make any difference since the flyback shorted and was doomed.

My only “experiment” with the CTC2B’s power supply was the replacement of the big selenium rectifiers with small silicon power diodes. This simple and logical change raised the B++ from 392v to 425v or 8.4%, well within RCA’s safety margin. How many members performed this same “experiment” on their sets??

Sorry to hear the news. I don't know the #2 postor, and I wouldn't have said that myself. In my viewpoint, this hobby would be zero fun without any challenges, and this is no different from a situation where someone might restore a '38 Cadillac, and take it out for a Sunday drive and have a kid run a red light or something. It happens.

There are several AKers with 21CT55s, and hopefully someone will speak up with a good FBT. If not, I'd suggest doing some comparison research to see if you could use a different Fly in that set. After all, the basics are the same for the horizontal frequency and deflection angles, etc., among most all 21" color sets. With a little qualIfied engineering, I bet a later model FBT could be used, since your set is a working demonstrator and not a virgin timepiece.

Charles

[JB5pro]

Am I understanding correctly that u used your apparent vast knowledge to experiment with a virtually priceless object that being the flyback? If so... shame on you!
If you took that flyback to it's limits you ought to be forced to restore it by chemically softening the coil so you can unwind it in order to determine exact length and specs for the new windings you will replace by hand. After you spend countless hours doing that maybe you will learn your lesson to respect things properly. All the knowledge needed to get the most out of those TV's has been uncovered by many great men here at Videokarma.

[Tomcomm]

But in the event you're not................I'll ramble on. My sacred FBT died of old age. It developed a short in the primary winding very near the core. I could see a tiny blue arc and a whiff of white smoke on the side of the winding near the core when I tried to restart the TV.

I did not cause this tragic failure, I wasn't even in the same room and the HV cage was locked. This FBT was toast, all dried out and brittle. It was non-repairable in my estimation. It had to be replaced.

[andy]

---

[Kirk]

Hey Tomcomm,

What did you ever do about the Flyback in the 21CT55?

Thanks,
Kirk

[Eric H]

Originally Posted by JB5pro

Am I understanding correctly that u used your apparent vast knowledge to experiment with a virtually priceless object that being the flyback?

The Mona Lisa is a "Priceless object" a Flyback is just a TV part.

Someone simply asked for help, lets keep the rude replies in check shall we?

[kx250rider]

Originally Posted by Eric H

The Mona Lisa is a "Priceless object" a Flyback is just a TV part.

Someone simply asked for help, lets keep the rude replies in check shall we?

Yes. I've been a member here for a few years, and I don't remember any case like this where other members "ganged up" on another. Not shame on Tom; but shame on the shamers.

There are at least two AKers in this thread, who are lucky Eric and the other mods are tolerant, and lucky that I'm not a moderator here.

Charles

[John Folsom]

Unfortunately, Tom's flyback suffered a catastrophic internal short in the primary winding. The heat generated actually caused the HV winding to slump. But there is still some hope. His flyback is in a box beside my workbench. It has been partly unwound, and the winding "recipe" recorded. I have not yet unwound the HV winding. This flyback is a bifilar wound type, with most of the primary and secondary windings wound with two wires in parallel. This makes it that much more difficult to attempt to rewind. The HV winding is a single strand of approx. AWG 38 wire.

I have wound 2 color flybacks so far, one for a 15" Motorola color set, and one for a CT100. The Motorola flyback works, but it has lower impedances than the original, and has a big "dip" in the top of the flyback pulse, which is causing some issues with the gated circuits. So just having the winding turns count recipe is not all there is. More experimentation will be required to attempt to determine what parameters need to change. As for the CT100 flyback, it too measures lower in inductance than the original, and if failed almost immediately upon installation in the set. Unwinding it did not reveal an obvious defect. I suspect wire handling is a critical issue.

I have taken a break from coil winding attempts for the last couple of months, it is just too darn hot out in the garage to slave over a hot winding machine. And other project have managed to get on the bench ahead of the coil winding. But in the next month or so I will get back to it, and see if I can make more forward progress.


Here is a photo of the winding machine, a George Stevens model 225-AMVP universal progressive coil winding machine, made in 1964. Some of you may have seen this at my ETF presentation on coil winding.

I will report progress as it is made.

[Pete Deksnis]

Originally Posted by Tomcomm

My only “experiment” with the CTC2B’s power supply was the replacement of the big selenium rectifiers with small silicon power diodes. ... How many members performed this same “experiment” on their sets??

Sorry to hear about your fly problem Tom. Does that mean your quest to engineer an S-video input to a CTC2B is on hold? ;-)

As to your question, yes, I replaced selenium with silicon in my operational CTC2 chassis, w/o a compensating resistance added, since in NJ where I lived at the time the line rarely went over 115 and was usually much lower (115 is the AC input spec for the CTC2). That chassis is now/still at ETF driving the rebuilt 15GP22 demo there, and since the line at ETF was nicely above 115, I added a 50-ft. extension to the power cord, which conveniently drops the line to around 115.

Pete