Quote:
Originally Posted by miniman82
I intend to start reducing the CRT Ultor HV from its present 34KV....'
and
'I jacked up the +400v B++ supply to above +420v'
I get a certain 'cringe factor', know what I mean? Not only was the 21AXP22 never rated for that votlage, but I severely doubt the flyback liked being driven that hard. How many times do we see people get warned again and again about HOT current, recapping, variac starts and the like? Seems obvious to me that the experimentation took it's toll, that's all I'm saying. I do hope the set can be fixed, but as I said I don't think you're likely to find an NOS one.
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I have to put my "2 cents" in here too.
I agree that the "turbocharging" is likely what killed the FBT.Going to OVER 420V on the B+?? If it was MY set...and I wanted to put silicons in I would have put some "series resistance" in line with the diodes, say, 50 ohms/10 watts or so. This would have kept the voltage from going over the limit.
And...34 KV?? Man...that is HIGH Voltage!! I have worked for a LONG time on tv's and I have only seen a FEW sets that high, such as a FEW sony prjoo sets, and a couple of 36" CRT's, that were 35KV. Most others are UNDER 34KV. And ALL sets with chassis tubes were under 28KV, to the best of my knowledge!! I would NEVER DARE to run a 21AX at 34KV--I would be afraid that it would kill it, and if not-- some REAL X-rays would no DOUBT be produced--since those tubes did NOT have x-ray protection.
Having said this--your experiment DID produce a BEAUTIFUL picture--like I could not BELIEVE!! No doubt the super--HV and boost had something to do with this.
IN short--I look at it like a turbocharged engine--and an OLD one, at that. Say--putting a 12 PSI boost on an old Chrysler 2.2L--and SURE you WILL get a LOT of power and performance out of it-- probably 250HP--for a SHORT time...but not for LONG--as the old engine(or fly and CRT) will NOT stand it.
Once you get the set working again...I would suggest series resistance with the diodes to get no more than 390 volts, and no MORE than 26KV h.v., and NO MORE than 225 MA Cathode current.
As for the "discourse" I agree some of it was a bit "heated", but as it was pointed out--CTC-2B sets are RARE--and the "keepers of the flame" do ANYTHING they can to PREVENT them--or parts like FBT"S-from ENDING UP IN FLAMES, and thus--allowed their passion for their collecting hobbies to steer the discussion. Myself, I have a CTC-5, and it is NOT working yet--as I have little time to mess with it, working and all--but it DOES have and a near--perfect, CR-70 tested, CRT--and the fly looks good--and when I DO "get into it" I will NOT "stress things at ALL.
I DO hope you are able to get your set going again though. Best wishes to you.
Jack.