RCA 21CT55 #8802897 is Dead

[mbates14]

I think miniman doesn't like you. thats what i feel.

[miniman82]

Originally Posted by RobtWB

For me I wouldn't get obsessed with voltages, currents, et cetera. The picture displayed tells just how close you are.

By that metric, I guess I should have ignored the 260ma current I first saw on the CTC-4 when I first powered it up. After all the picture seemed OK, and it's not like I can't just walk down to Radio Shack if I blow the flyback.


I don't care what Tom does to this set Bates, it already lost it's historical value when he smoked the flyback. I'm more interested in what other people are getting from Toms 'work'. I just don't want people to take anything from this thread and use it on another set, because it would be extremely dangerous to do so. 27+kv at the CRT? No bueno, plus there's just no way he has 128ma HOT current while doing so. I can promise you that all 3 of my sets would be at easily twice that value if I tried the same thing, so either he's reading it wrong or telling us the wrong number.

[Steve McVoy]

This badmouthing is getting annoying. I'd urge everyone be respectful to those who post here. Calling someone's post BS has no place here, when the intent of Tomcomm is clearly to get help from the collecting community in dealing with the failure of his flyback.

[miniman82]

No sympathy from me, it's clear why it failed in the first place... It's not disrespect, it's the truth.

As I already said, I'm most interested in others not being mislead. He can do whatever he wants to the set, I don't think I'm being disrespectful for saying that. I simply want people to be HONEST with their assessments, that's all. Telling us there's only 128ma on the cathode is misleading, and to the uninformed observer, irresponsible.

Let me illustrate: what's the lowest cathode reading any of you have seen on your sets? Lowest I ever saw was 178ma on my CTC-9, and it took a LOT of tweaking to get there. Most would be happy with 200...

[Steve McVoy]

miniman82, there are many reasons he may have come up with 128ma other than an attempt to mislead people. There may be problems with his test equipment, he may have made an error in how he took the measurement, or it might be because he is using a flyback that was not designed for the set.

I still say you should tone down your talk, and stop accusing people of misleading.

[miniman82]

I'M NOT YELLING AT ANYONE.

Anyone who knows me knows that I'm a very easy person to get along with, just ask Mark. Sometimes it's hard to get meaning through some words on a screen, that's what's happening here. I call things like I see them, but sometimes people take it the wrong way. I'm used to it, doesn't bother me anymore. Why are people so touchy-feely anyhow? It's not like I'm threatening anyone...

For the 3rd time now: I'm simply pointing out that there's an obvious lack of hard facts here, and it would do everyone here a lot of good to know what's really going on. Most of all is Tom- I of all peple don't want to see him burn this thing down a second time, but I'm telling you all that is exactly what's going to happen if he doesn't figure out what his HOT current really is. Is that not a good thing, or am I being disrespetcful still?

[Eric H]

May I suggest instead of saying "I'm officially calling BS:" say, "that can't be correct"

Instead of "there's no way in hell you have only 128ma on an output tube"
try "your readings may be in error."

Offer some advice on how to remedy the problem instead of calling him a liar.

You have been on his case for Hot Rodding his set since the first post.

It is hard to convey tone through text but a few less inflammatory words would help.

[old_coot88]

I didn't hear it mentioned (or might have missed it), but was the OP using a digital or analog milliameter to measure HOT current? As digital meters are known to go nuts in applications involving high level pulses and waveforms, I sure as heck would use only an analog meter there. And I would do it at the cathode, not the B+ fuse.

As for another poster's statement, "For me I wouldn't get obsessed with voltages, currents, et cetera. The picture displayed tells just how close you are."

Yeee-ikes! That advice might pass muster with B&W. But with color, it is absolutely critical that the HO cathode current be kept within spec or lower. Even with the later 6JE6 and 6JS6 (in Zeniths) we would strive for no higher than 210ma to give the tube and flyback a reasonable chance of survival. 200ma was ideal if width and regulation were adequate. Bill(oc)

[sampson159]

i agree that sometimes the comments get a little offensive.you might be the greatest guy in the world but when you get in front of the computer, a new personality immerges.i found toms postings to be informative and enlightening.if he misquoted some info or in your opinion,to be wrong,then you dont have to be insulting.also,no need to get upset with anyone in this forum.these guys will help you in ways you cant imagine.outside of a few,they are friendly and courteous.reading posts from people arguing is just like being married again.dont want to hear it or see it.as i am an old timer who worked the wrestling business,i watch mma,boxing,some wrestling,etc.i come to this board to learn and relax.maybe if you folks want to argue and fight,send private messages?thanks for letting me post and everyone ENJOY this wonderful forum we have while we can!

[zenithfan1]

Well said, Ron. Pm's are a good idea for stuff like this.

[colorfixer]

...and what we're forgetting here is that where it not for the fact that he did anything with the set, most of our 'YL's would have had the set carted off to the landfill to get it the "hell out of the garage" to make room for gardening supplies.

The fact that someone is trying to do two things:
1. *Learn* something about the design and the components' capabilities,
and
2. Move forward with assisting in the reproduction or replacement of what would otherwise be an unobtainable part, knowledge of which will benefit each and everyone in the hobby.

..should be commended.

I don't think we'd be having anyone in the commercial world research the production of tube circuit flyback transformers.

Heck, I can't even get someone to rebuild or even supply a CRT that there were at least 100000+ built by Zenith in the day, and I've posted requests on nearly every forum on the interweb over the past three years. And to boot, the tube I need is sought after by the owners of what is at least 10^4 more sets than number of 21CT55s bulit in the first place.

Move on.

We will all benefit when the "art" of winding new transformers is perfected (rediscovered), just as we all benefit when a number of 15G's were used in the development of a rebuild procedure.

[Tomcomm]

Seems the latest miniman issue relates to my posting of 01-29-11, 02:44 PM. Since RCA connected the 6.3vac heater ground to the 6CB5 HOT cathode ground they obviously didn’t want Service to measure HOT cathode current. Sams detailed service procedures made no mention of measuring HOT current so I have always measured FBX system current at the HV fuse. assuming this was a good approximation of HOT cathode current. The 128ma Hot cathode reported in the post was made on a DMM which was obviously wrong.

When miniman delicately suggested this reading was suspect, I remeasured with an analog VOM and surprise! I got the exact same current at the HOT cathode as I got at the HV fuse, both were 170ma, quite modest for well over 27kv ultor, right? I immediately edited my original post and gave the edit reason “Corrected some measurements”. There never was an attempt to fool myself or irresponsibly mislead the rest of you members as was stated by miniman.

[andy]

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[rca2000]

I seem to recall reading in RE magazine a long time ago that High OR LOW current in the HOT ckt is bad, somehow, if the current is too low it STILL will "throw things off balance" and cause heating n the FBT. Remember...we ARE dealing with a "tuned ckt" here, a little off either way can cause problems.

And 128 MA. where 200 should be is WAY off IMHO.

[andy]

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