Help Identify My New Zenith

[andy]

...

[TinCanAlley]

Originally Posted by andy

You always want to do gray scale with the color off, or with a pure B/W signal. The G2 controls adjust the brightness of each color, and the taps adjust the contrast of each color. You adjust the G2 for neutral balance of dark gray (almost black), and the (drive) taps are used to balance high brightness areas of the picture.

My one complaint about Zenith TVs from the 70's is that to save money they replaced the drive controls with those three position jumpers. It makes it impossible to get perfect gray scale unless you get really lucky with the CRT.

Having said all that, the first thing I would do is measure the G2 voltage to all 3 guns to make sure that the G2 controls are working properly. Normally, you should be able to adjust the service line from black to fairly bright on all 3 guns. If the G2 supply is low, or there's a problem with one of the controls, you won't be able to adjust it properly.

Where would I measure the G2 voltages? From the CRT socket? If so, do I just pull the socket off while it's operating, put the black probe to chassis ground and stick the red one in each socket and note the voltage? Do I move the G2 control back and forth while measuring?

I have the service manual, but it's the electronic version and it's not clear enough to note all the voltages on the socket. These are the ones I can read okay, but the 13 and 4 are blurry:

Pin:

2- 143V
11 - 142V
6 - 142V
7 - 36.4V
12 - 36.4V
3 - 36.4V
5 - 540V
13 - 640V
4 - 540V
9 - 3.5kV

If those voltages are correct, I can do all but the last 4 as my meter only goes as high as 500V. Oh, and are those AC or DC volts?

[zeno]

Originally Posted by TinCanAlley

Where would I measure the G2 voltages? From the CRT socket? If so, do I just pull the socket off while it's operating, put the black probe to chassis ground and stick the red one in each socket and note the voltage? Do I move the G2 control back and forth while measuring?

I have the service manual, but it's the electronic version and it's not clear enough to note all the voltages on the socket. These are the ones I can read okay, but the 13 and 4 are blurry:

Pin:

2- 143V
11 - 142V
6 - 142V
7 - 36.4V
12 - 36.4V
3 - 36.4V
5 - 540V
13 - 640V
4 - 540V
9 - 3.5kV

If those voltages are correct, I can do all but the last 4 as my meter only goes as high as 500V. Oh, and are those AC or DC volts?

Without going into much detail.........
I always pulled the IF jack when doing a grey scale if it was easy.
This gives a totaly dead raster or line.
Pin 9 is focus so not to worry for now. Pins 5-6-13 are G-2 and
may concern you. Measure at the chassis unless you have a test socket.
The only thing in the socket is spark gaps & 1 K resistors.
they do go bad but usually the focus pin from too much focus voltage
or constant high humditity.....
I highly recomend a rebuilt Fluke meter
off e-by. Got them for both sons & do more then the cheapo
meters. Also can drop them, hit people with it etc & will keep
running. Just be sure it goes to 1 KV DC. They run abt $75
but will last your life. Beond 1 KV you need an HV probe..........

73 Zeno

[TinCanAlley]

Originally Posted by zeno

Without going into much detail.........
I always pulled the IF jack when doing a grey scale if it was easy.
This gives a totaly dead raster or line.
Pin 9 is focus so not to worry for now. Pins 5-6-13 are G-2 and
may concern you. Measure at the chassis unless you have a test socket.
The only thing in the socket is spark gaps & 1 K resistors.
they do go bad but usually the focus pin from too much focus voltage
or constant high humditity.....
I highly recomend a rebuilt Fluke meter
off e-by. Got them for both sons & do more then the cheapo
meters. Also can drop them, hit people with it etc & will keep
running. Just be sure it goes to 1 KV DC. They run abt $75
but will last your life. Beond 1 KV you need an HV probe..........

73 Zeno

Do you mean 5,4 and 13? The leads to the socket go though to under the chassis. Do they have test points somewhere on the top of the chassis?

I'll see about unplugging the IF lead and check for a rebuilt Fluke or borrow my brother's. Will still get one, but don't want to wait any longer than necessary to get this puppy up and running. The safety caps will be here Tuesday.

Thanks

[andy]

...

[TinCanAlley]

Originally Posted by andy

4, 5, and 13 are the G2s. You won't be able to fit a meter probe in the socket (don't force it, or you'll ruin the socket). The exact voltage isn't important, but they should all cover roughly the same range when adjusting the corresponding G2 control. They should max out around 900v or so. You'll probably have to measure it from under the chassis.

Thanks. I see they run under the chassis to the G2 pots. I will have to put the set on its side, take the base off, take the underside chassis cover off and leave it like that so I can measure the voltage. Since each one of those leads has more than 500V, I'll have to get my hands on a DMM that can do more than mine.

Is there any danger of a short if I accidentally touch any other lead on the G2 pot or the body of it?

Thanks

[zeno]

Originally Posted by TinCanAlley

Thanks. I see they run under the chassis to the G2 pots. I will have to put the set on its side, take the base off, take the underside chassis cover off and leave it like that so I can measure the voltage. Since each one of those leads has more than 500V, I'll have to get my hands on a DMM that can do more than mine.

Is there any danger of a short if I accidentally touch any other lead on the G2 pot or the body of it?

Thanks

Sorry about the pin mix up
You could slip & put 800-900 V where it doesnt belong so
use a clip lead to play it safe. Slip happens when working in
dark, awkward conditions. When doing it for a living you just
measure away for the sake of speed but you can relax &
take your time. Less mistakes that way.
BTW when working on its side the purity will usualy be bad,
just ignore it.

73 Zeno

[TinCanAlley]

Okay, got the safety caps in and double checked I didn't mess something up while cleaning. Made sure I didn't dislodge any transistors or cause any two or more leads to touch each other. All was well upon start up.

I used clip on leads on the center post of the G2 pots (that's the lead to the CRT socket). I measured each G2 to be between 426 with pot down and 752 with pot up. So I'm assuming those numbers are good.

Next...as I'm typing the set is warming up so I can try the grayscale again. Hopefully I can get the red raster line this time.

Wish me luck.

[TinCanAlley]

Well I managed to get a dim red raster line and adjusted the blue and green to the same level (really the best I could guess as a dim line looks like a dim line). From there I got a b&w image and adjusted the taps to a screen that had just a very slight blue tint to it. Moving the tap lower made the screen a bit red. So I put it back. Should I try moving the blue G2 down a bit?

The convergence is a bit messed up. I'll have to wait until Thursday when I get the pattern generator. I'll use it to converge the center dot, then do a purity and finally do a convergence. Hopefully all will go well.

I do have a question about picture height and width. On my other CC2 it has height and width adjustments. On this one I don't see them and they aren't listed in the SM. The overscan is a bit too much and I'd like to reduce in all directions.

Thanks.