Help with ctc9

[mstaton]

I have a ctc9 and I installed a used 21fbp22 crt. Emissions are very good, life test is good but green is a little weak. No shorts. The problem is my HV cannot be changed but if I unplug the CRT, I can adjust it some. Max when crt connected is 21KV. Cathode current on the HOT is 180ma. Also if I turn up the red drive, the HV drops like a rock. Brightness could be better. I replaced most of the caps. B+ is right on spec, Color is good. All tubes are good. Focus has to turned all the way to one side to be good. Any thought on whats causing the HV to drop upon red drive adjustment?

[timmy]

well sounds like what i have been going on with a ctc15 my hv wont go above 16-18kv. be aware dont run the focus coil in clockwise to much it will burn up, with the voltage rise and did you try using a crt tester to remove shorts in the crt, the little fuzzy like things that get in the way of the gun heaters but REMOVE SHORTS ONLY function only because what your saying says what i have been working on here with my ctc15 but i had other things going on with the set. i had the same with the red but the red always seems to be the tough color in an old crt.i had focus problems as well and also changed all caps but i am getting to the final problem. my crt also a 21fbp22 checked out super good but it also had the little shorts that had to be burned out which made a big difference. how is the 6bk4 regulator tube, try another? how about the rectifier tube, try another? there maybe a slight short on that gun since it would not hurt to check for shorts like i did you might be surprised as i was at the result, but again SHORTS ONLY do not use rejuvenator. i had a b&k 440 crt tester that i used. the emissions were good on mine but improved alot after removing shorts and my crt tester did not show any shorts within the crt because it depends on where they are and i showed nothing, but they were infact there. 21 kv is not all that bad since i think the norm could be 21-24 kv.i learned alot since joining this site from alot of members but of course some will tell you things that you should not do and it comes down to you making that choice as to which part of advice you will use. crt bias is it raised up or if the color is good adjust the guns but on the lower side. this thing i speak of with shorts in the crt that dont show, i was told this by a tech from the 60s that worked on these sets and he is the one that told me of this and that it wont hurt to check using the shorts only and sure enough it had some, little sparkers on each gun, one at a time. well i hope this helps alittle bit because im still weeding out a few things on my set, so i know whats happening there it can make you crazy like it has to me.

[mstaton]

I replaced the HOT(6BQ5), regulator tube(6BK4) and HV rect(3A3) with NOS. I can get up to 25-26KV down to about 19KV. So that solves the HV issue. When I turn the brightness down it jumps up to 30KV and also I have a dark vertical bar in the center of the screen. Any ideas? See pic

[DaveWM]

if it goes to 30kv with the brighness down, then I would guess the shunt tube is not operating properly (should be clamping it) or the HV is just set too high.

did you check the cathode current of the 6Bk4? I am not sure about that early of a set, but would guess the current should be between .5 and 1.5 ma depending on brighness and contrast settings (higher ma with CRT dark).

Just a guess here but maybe you just have the screens set too high. I would back them down so when the brighness is fully CW the pic is just a bit brighter than normal viewing, set them all for good grey scale, then adj the drives to get good whites, set the HV for 23-24kv check the shunt current again and see if it varies with screen brightness and if the HV holds steady.

The fly can only produce a max power output, the shunt clamps it down if the CRT is not drawing too much, and lets off when the CRT needs more.

if have the CRT biased incorrectly or the G2 voltage is too high then the CRT will draw all the flyback energy leaving the shunt nothing left over to clamp, if the draw is more than the max, the HV will drop. From what I gather the optimum is clamp .5ma on a dark screen this way there is always some flyback in reserve so the HV will not drop.

If the shunt current is high even in a bright screen, then there is a problem in that circuit. there is not a lot in there, I would check the resistors 1st then the pot then the caps in that circuit, in that order (after tube sub that is).

good luck with it.

[ctc17]

That bar is interesting. Was it there before the tubes changed? Wonder if that could be something in the damper or video circuit.

[Electronic M]

I find it amusing that the guy in the sceen appears tobe stareing at the bar produced by the set. Was that planned?

Tom C.

[DaveWM]

is the dark bar there when the color is turn all the way down? How about the color turned up and the contrast all the way down? maybe check the blanker tube?

[DaveWM]

it would be good to scope the video at the grid of the CRT of a test pattern and see if its good then work your way back

[mstaton]

That bar turned up after the tube change interestingly enough. I'll check the regulator circuit. If I turn the screens down anymore the picture will be dim. Red is all the way down and seems good there. If I turn up the red background I lose some HV but not as bad as before the tube change. I know the CRT is good at least that's what the checker leads me to believe. I have to have the brightness turned up pretty much all the way and the contrast almost all the way up and i don;t think its bright enough. I have a scope but don't know enough about them to use it. I don't have a manual for it either.

[DaveWM]

I would be looking at the video amp tube as well. contrast should not need to be nearly all the way up. you need to check the voltages at the pins of the CRT and see if anything odd going on there, again CRT bias can mess up HV. With the contrast control near max it should be very dark in the dark areas. Have you recapped the cathode bypass of the video amp tube? I have had several set that have a weak cap there resulting in loss of gain (contrast).

if you get a good HV setup and that bar is still there, your best bet is to break out that scope, as good a time as any to start using it. I use mine all the time on TV work.