Hi Gang,
I just purchased an RCA CTC53 color portable and need a 18VBDP22 or equivilent. Its the typical low voltage focus (Einzel gun) CRT that was popular in RCA portables of the early 70's. If any of you have one to sell or know where i can buy one from, please let me know.
I thought i had gotten a good deal for $5 especially when i got it home and it played. I had just finished doing a badly needed convergence job and adjusted the vertical height and was sitting back watching it, making sure it didnt develop any problems before i put the back on. After about 30 minutes of playing time the raster went extremely dark. I looked in the back and saw the picture tube neck glowing neon purple. Needless to say i unplugged it immediately. I put my crt checker on it and got no readings except for filiment continuity. The filiments still light but other than that it has no readings. I turned the set back on with crt socket unplugged and hv arced like crazy off of the tube pins like it would if it had gone to air. Since the filiments still light it has me scratching my head since i've never encountered this particular problem before. Can anyone explain if anything else could have caused this besides the CRT going south and why would this have happened so quick? It had a nice picture just before this happened and had good drive on all three guns with good color,brightness and focus. The picture was good enough that i didnt even think of putting the tester on it before it conked. Any advice or suggestions would surely be appreciated.
Thanks,
Tony

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Thanks Andy,
Thats probably what i'll do if i cant locate the original type crt. Either way i'll need one that will fit, whether it is the low or normal type focus set-up. I hope i wont have to resort to that as i'd like to keep it original as possible. The set is otherwise mint. I realize this model isnt as collectable as some but i had one identical to this when i was a kid and was my first color set. Thats why i want to get it going again. If i had to resort to using the regular type crt, i would prefer one with the etched glass on it. I would also need help with comming up with the circuit needed to supply its focus voltage.
I guess from it being stored for a couple of years with being used rarely just before that and then being played for awhile when i got it is what aggravated the crt's quick decline. I played it for three hours the night i bought it and then 30 minutes the following night after i got it back to proper alignment. The one thing i did notice is when i turned it on both times....it took longer than it should have for the raster to come up which had to be at least a couple of minutes after sound was already on. During first check-over all the tubes tested good to excellent (yes Doug...even the 6GH8's...lol!) as well as the electrolytics and the HV was in normal range so i just attributed the delay in raster to it being unused for awhile. Although the inside was dusty, it didnt arc or for that matter make any static noise when HV came up like i'm accustomed to on older dusty sets. The flyback was running only lukewarm so i figured all was in good shape to converge and align and put it into service. Since the picture was pretty good, it didnt occur to me that the crt was on its way out so i didnt test it until after it quit. If none of you think anything else could have caused the crt to fail then i think it should be ok just to replace the crt and go with it after checking everything again.
Tony

The CRT may indeed be bad but try these tricks first:
1. Make sure the CRT outer aquadag coating is grounded

2. try gently tapping on the CRT neck with the set on. Use your isolation transformer if you have it...the chassis is "hot". Carefully take an insulated tool and tap the neck...this worked for me to fix a Magnavox set with CRT neck arcing.

Also for some reason it takes a relatively long time for the picture to come on with this type set...seems like at least 45 seconds. The sound comes on before the picture does. I don't know why the set is like this but it is normal--although several minutes is probably too long for normal.

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Hi Andy and Chad,
No, it doesnt produce a raster now. It did at the time of the failure which basically you could see something on the screen to know it was still working but after i unplugged it when i saw the neck glowing it never came back. I also tried the neck tapping trick and checked the grounding of the aquadag with no success.
Chad, thanks for the input on the delay in the raster comming on. I had the first generation of this model in which the raster came on like any typical color set so i thought that by this one having the delay that something odd was going on. I'm glad to find out that this is normal. I guess the only thing to do now is just try to locate another crt for it.
Thanks again,
Tony

Do you know what CRTs may substitute for the one you need? I have an 18" Color CRT from a Sears set. The number is similar to the one you need, but has an A in it. I will try to look at the CRT and write the number down tomorrow.

Hi Peverett,
I dont have a crt sub book new enough to cross this one but as long as its a delta style gun and is not perefectly square like the newer sets (xl-100 is an example of the more square tube) then i should be able to get it to work in my set whether its a normal or low focus voltage tube.
Thanks,
Tony

The crt that I have is a MV18VAHP22. It does have a triangular gun structure.

Tony,

have you pulled the tube out?
It would be interesting to know if the getter has gone white.

Eric

It is not in a TV, but loose. I have checked it before and it was good. I will check it again this weekend and post its condition.

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Tony, do you think that you can still make the CRT I have work, given that it is a high focus voltage CRT?

Hi Peverett,
Andy said it was possible to make a higher voltage focus type crt to work in a lower focus tv by adding a focus bleeder to the anode. I'm still researching that idea just in case i have to go that route, so if it seems easy to do then yes i could probably use your crt. I'll let you know and thanks.


Update:
On checking the getters for Eric i found the problem. Obviously at one time this tube had been rebuilt even though it had what looked like the original RCA lable on it. Where the neck was fused to the bulb i found a very slight almost invisible speck in the seam. On closer inspection with a magnifier it turned out to be an air bubble that probably opened up when the tube heated up after not being played for years. You can stick the point of a needle into the bubble. I checked it again with the tester for the heck of it and now the heaters dont glow anymore so it comfirms that it went to air. I couldnt find any getters on the neck or any traces of any ever being there. No white residue in the neck anywhere either. Is this possible?

I guess its back to searching for a good tube and if i cant locate a low voltage focus one then i'll get the one from Peverett. Of course then i'll need help with ideas in making the focus bleeder for it.
Thanks everyone!
Tony

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Some older types of computer monitors have the focus bleeder, also some other TV's from the late 70's/early 80's. A lot of the time there is two wires going into the anode connector....one is the HV out from the rectifier and the other is the HV in to the focus divider.

I'll look tonight and see if I have any junk sets/monitors with the focus divider.

The later RCA tube type portables (later model ctc-52, also ctc-66? etc.) use a high voltage focus CRT and use an HV tripler off the flyback rather than the 3A3 rectifier and low focus voltage crt.

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i am going to a friends place to get some crt's and will see if any 19" low focus are there.
if so i will get it and its yours for postage.

Would this one work? 18VAKP22

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