Carbon composite in place of carbon film

[TinCanAlley]

Originally Posted by DaveWM

its not that you are aiming for those that is just what sams got, my concern is if you deviated from the correct G2 setup procedure, then the bias of the tube may be off, making other things (maybe the jail bars) become an issue.

just do the setup as defined in sams, check the voltages and post back the results if brightness is still an issue then need to look at the other voltages and try to figure out why, brightness should not be an issue with a good tube with correct HV and pin voltages.

I'll readjust them first thing on Wednesday per SM instructions.

[TinCanAlley]

Originally Posted by DaveWM

its not that you are aiming for those that is just what sams got, my concern is if you deviated from the correct G2 setup procedure, then the bias of the tube may be off, making other things (maybe the jail bars) become an issue.

just do the setup as defined in sams, check the voltages and post back the results if brightness is still an issue then need to look at the other voltages and try to figure out why, brightness should not be an issue with a good tube with correct HV and pin voltages.

Okay, I could not go the setup switch approach. The only G2 that put a line on the screen was the blue. The red and green wouldn't show. So I brought up a grayscale pattern and adjusted it that way. After doing that and adjusting the taps, the red voltage was 590V, blue was 550V and Green was 540V. The SM has the Green at 640V, Blue at 540V and Red at 590V. So other than the Green, the other two are pretty close.

Now I do have more brightness range, so that is good. As for the jail bars, they're still there. I changed the diode since I had to unsolder the existing to test. I didn't bother with the 100K resistors as I have the scope now and figured I'd try that before more part replacement.

[DaveWM]

you need to check the other voltage at the pins of the CRT the cathodes/G1 and G2.

It does not follow that you can not get the setup to work with the switch. If the crt test good it should work, if it does not work there is a problem.

[andy]

...

[TinCanAlley]

Originally Posted by DaveWM

you need to check the other voltage at the pins of the CRT the cathodes/G1 and G2.

It does not follow that you can not get the setup to work with the switch. If the crt test good it should work, if it does not work there is a problem.

Okay, here's where I get lost. Finding the G2 lines was easy. I just connected to them at the pots. As for the G1 lines, I don't know which ones they are. The G2s are all white with red, blue and green stripes. Then I have yellow wires with red, green and blue stripes and solid color red, green and blue wires. That makes three sets of wires and no indication in the SM as to which sets are which. I do know the black is focus, though.

[TinCanAlley]

Originally Posted by andy

I would be looking at the G2 supply. The fact that you can't get a setup line indicates that there is a problem. You should be able to easily get a setup line on all 3 guns. Ignore the exact voltages in the service manual as they will vary from one CRT to another. What is the maximum G2 voltage you can get? It should generally be around 700-900v with the controls at maximum.

I wasn't able to get a setup line on my CTC40, and it turned out to be a bad HV diode in the circuit that supplies the G2. In my case, it also caused the focus range to be off.

During testing, the range for each G2 control was roughly 450 to 729. The reading was taken directly from the output tap on the G2 pot.

[DaveWM]

the best way is to simply pull the crt socket back just enough to expose the pins, then using the rat shack spring loaded prob you clip on to one pin at a time (neg to chassis) and get a reading. you want the socket to be on enough to still work the CRT. As far as what pin is what, you should look up the CRT (google) and it will be listed along with pin out. stay away from the focus pin it will be the one that has space between it and the other pins on both sides.

dont try and just use the prob directly to the expose pin, it can be done but you risk slipping and shorting out on pin to another. far better to get it all hooked up and make sure nothing is shorted then power up, get a reading, power down and move to the next pin.

oh one last thing, if you do this a lot you use a socket adapter that goes between the CRT pins and the socket, it has test point that are clearly labeled that make checking pin voltage easy.

[TinCanAlley]

Originally Posted by DaveWM

the best way is to simply pull the crt socket back just enough to expose the pins, then using the rat shack spring loaded prob you clip on to one pin at a time (neg to chassis) and get a reading. you want the socket to be on enough to still work the CRT. As far as what pin is what, you should look up the CRT (google) and it will be listed along with pin out. stay away from the focus pin it will be the one that has space between it and the other pins on both sides.

dont try and just use the prob directly to the expose pin, it can be done but you risk slipping and shorting out on pin to another. far better to get it all hooked up and make sure nothing is shorted then power up, get a reading, power down and move to the next pin.

oh one last thing, if you do this a lot you use a socket adapter that goes between the CRT pins and the socket, it has test point that are clearly labeled that make checking pin voltage easy.

Well I used the hook probe and got all the voltages. The only ones I know for sure are the G2 leads. I'm assuming the G1s are the yellow wires since their voltages are around 140V which I believe is the cutoff voltage? I was unable to find anything on the internet searching for my CRT model and pinout.

I'll put the values in the SM first and then actual.

SM Values Actual Values

2 = 143 153
6 = 142 144
11 = 142 147

3 = 36.4 33.4
7 = 36.4 33.4
12 = 36.4 33.4

4 = 590 600
5 = 640 548
13 = 540 540

All the numbers seem good and within range.

Pin

[DaveWM]

hmm, well thats odd that you can't get the setup to work then.

my service manual shows 180v at the collectors of output transistors when in the service mode. check that. again extreme care with the probes or you can smoke a SS device is a fraction of a second.

[TinCanAlley]

Originally Posted by DaveWM

you need to check the other voltage at the pins of the CRT the cathodes/G1 and G2.

It does not follow that you can not get the setup to work with the switch. If the crt test good it should work, if it does not work there is a problem.

Kind of late, but my skills at reading the schematics must be getting better. I just found that there are test points for the G1s at the chroma gain taps. Seems T, S and R are the G1s and you can measure the voltage from there. I just did that and got the same voltages there as the pins (well within a volt).

[DaveWM]

good now check them in the service mode. I think it should be close to the 180v

[TinCanAlley]

Originally Posted by DaveWM

hmm, well thats odd that you can't get the setup to work then.

my service manual shows 180v at the collectors of output transistors when in the service mode. check that. again extreme care with the probes or you can smoke a SS device is a fraction of a second.

Will have to flip her over for this one. The output transistors are TO39 casings and the legs were cut so they sit flush to the socket. I'll have to do it from the bottom.

[TinCanAlley]

Oh, never mind. Seems the test points I found are the collectors you mentioned. No need to flip her.

[DaveWM]

I am a little behind you, try checking at those same point you found, should be close as I think there is only a 1k resistor between them and I doubt there would be a lot of voltage drop.

[TinCanAlley]

Originally Posted by DaveWM

I am a little behind you, try checking at those same point you found, should be close as I think there is only a 1k resistor between them and I doubt there would be a lot of voltage drop.

Okay, here's what I got from the output collectors at the test points in setup:

Red = 197V
Blue = 184V
Green = 192V