ctc12 clone beam current

[DaveWM]

you can still get a solid 25kv on the raster from full bright to full dark right?

if so you need to focus on that crt setup. starting with the checks of voltages at the yellow stripped leads as detailed above. The setup does not seem to be working, need to find out why is so touchy.

[Username1]

So lets say you put on the Honeymooners, there is a nice steady watchable picture...?
And this blooming that happens, it's during regular programing ?? And if it is -
when you leave the G's Screens, and Kine Bias alone, and turn the front of the set
brightness, and contrast back and forth slowly it seems to work ok.... or not...?

And if you turn to a raster only spot no snow between stations between detentes,
you have a blank screen and if you leave it, the screen is steady...?

And in that spot, adjusting only screens, or bias, causes the blooming...? Are the drives
not effected.... They don't cause any blooming....?

.

[timmy]

i just looked at the crt ground where the chassis makes contact with the foil strap and its black on the chassis like coal dust as if its not making good contact and some wipes off.

[timmy]

yr 200v hi low 232v yg hi217 low267 yb low 216 hi 266 v bias pot up and down bright screen

[DaveWM]

all 3 of those yellow with stripe should be closer to 300v (crt cathodes)

all 3 of the solid color RGB wires should be closer to 200v (crt control grids)

all 3 of the white with stripe should be around 600's (crt screen grids)


the yellow strip gets it voltage from the plate of the 12by7 should b about 300v pin 7

with the raster set to normal full brightness check those yellow striped wires again.

[timmy]

yellow wires red 250 green 255 blue 258 v
white wires red 730 green 622 blue 750 v
solid wires res 192 green191 blue193 v

[timmy]

these voltages are from setting it up for best picture and b&w screen. i can set them by voltage readings from sams but it wont be right. and the hv is at times low and does alittle dipping.

[timmy]

looking down on 12by7 going counter if thats 7 its 145 volts

[DaveWM]

Originally Posted by timmy

yellow wires red 250 green 255 blue 258 v

and that is with the kine bias fully CCW? no wonder it blooms instantly
and turning the kine bias CW just reduces those even more?

You did say this CRT tested fine for emissions and cut off right?

[timmy]

Originally Posted by DaveWM

and that is with the kine bias fully CCW? no wonder it blooms instantly
and turning the kine bias CW just reduces those even more?

You did say this CRT tested fine for emissions and cut off right?

the crt cutoff was close for the red but better on the other, and the bias is ccw. otherwise emissions good

[DaveWM]

Originally Posted by timmy

looking down on 12by7 going counter if thats 7 its 145 volts

that cant be right, pull 12By7 the tube out and check that voltage again (with tube out), should be at least 300v

[Electronic M]

One thought on the HV regulation that only works without video issue: On my CTC-12 clone Silvertone, the HV regulator circuit has a lead (from it's control grid IIRC) that goes to the output of the luminance video amp through a high value resistor. I think that allows the video to have control over the HV, and if that line is bad on your set it could help explain the poor regulation with video present.

[DaveWM]

I asked him to look for that, think it was a 12meg. I know it was added starting on the CTC-15's

would be interesting to add it to an earlier set just to see if there is any noticeable difference.

[DaveWM]

I have him running down bias voltage on the CRT. they just seem way off.

I think the best idea is set it up for the decent brightness raster (not using the setup procedure since that does not work). with a solid 25kv from full bright to cut off.

then

get both the silvertones out, and compare one CRT lead at a time mainly looking for the bias between K and G1 and the required screen voltages, maybe even the horz out cathode current. set up both with rasters of approx equal brightness and HV both at 25kv.

tough dogs require really thinking thru the issue, in this case getting the HV under control (by having good shunts that do not short out) is just eh begining.
the hard part is determining just how bright max bright, how strong is the CRT, and whats going on as the controls are adjusted.

[timmy]

where was that 12 meg resistor ?