G07: soooo much red

texasmame

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Have a G07 that had too much red. Recapped and the only thing that changed is that the red looks much nicer now. ;)

I then swapped out the X101 and X102 (or whichever they red transistors are on the chassis and neckboard) with the transistors with other corresponding transistors for the green channel - again, no change. Also did the same for the pots - nada.

So, it wasn't the cap kit and it apparently isn't the transistors or the pots for the red color as swapping them out with green got me nowhere.

I have a G07 that I recapped and put a new HOT and power regulator, etc. and it's solid. I put this chassis on that tube and it was fine - so it's not the tube.

Between this and the damn k6100 mystery, I'm pretty beaten down. :(

Ideas?
 
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Here's a pic. Scores and such missing on this screen since they are red. They do show up as the screens progress and their color changes.
 

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Look at the schematics... Check the transistors and diode in the red color drive circuit on the main chassis board... It's either something in that simple circuit or something on the neck board.

There are very few items to check in the red circuitry.

Also, did you install the caps in the correct polarity?
 
When you swapped the transistors, did you get all 3? It's X101 and X102 on the main chassis, and X102 on the neck board.

I'd also go over matching components in the neckboard, reflow the CRT socket and input header pins (which you probably already did with the cap kit).

The color drive circuits are funny in that open components can result in over-driven instead of missing colors as you might think.
 
Look at the schematics... Check the transistors and diode in the red color drive circuit on the main chassis board... It's either something in that simple circuit or something on the neck board.

There are very few items to check in the red circuitry.

Also, did you install the caps in the correct polarity?

Yeah, I'm actually looking at the schematics now and may just shotgun the red circuit, starting with that lone diode.

I had already swapped the transistors in that circuit for the ones in the green to no avail, so thinking it's not them.

I think I'll go and double check the polarities of the caps while I'm at it, but I am very careful to check those as I do them. Still, certainly possible that that is an issue.
 
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When you swapped the transistors, did you get all 3? It's X101 and X102 on the main chassis, and X102 on the neck board.

I'd also go over matching components in the neckboard, reflow the CRT socket and input header pins (which you probably already did with the cap kit).

The color drive circuits are funny in that open components can result in over-driven instead of missing colors as you might think.

Yes, changed 'em all out with the greens. Same with the pots.

Did all that reflowing, too. Gack!
 
There is a 5-pin connector in front of the video input pins. It goes to the neckboard. Unplug that. If the red goes away, then the problem is most likely on the main chassis. if it stays red, then the problem is on the neckboard...
 
Oh, and double check the neck pins. I once had a pin bend over and short to another, causing the color to stay on...
 
There is a 5-pin connector in front of the video input pins. It goes to the neckboard. Unplug that. If the red goes away, then the problem is most likely on the main chassis. if it stays red, then the problem is on the neckboard...

Great. I was looking for a way to isolate the neckboard or the chassis. All I could think of was splicing in my known good neckboard and really didn't want to hack those wires.

Edit: removed that and the screen was completely blank - no picture at all. BUT - no red.

So, it may well be the neckboard, correct?
 
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Great. I was looking for a way to isolate the neckboard or the chassis. All I could think of was splicing in my known good neckboard and really didn't want to hack those wires.

Edit: removed that and the screen was completely blank - no picture at all. BUT - no red.

So, it may well be the neckboard, correct?

May not. Replace it and remove the video input connector and check again.

And you can always swap the red and green input wires to where they solder to the neckboard, to see if it changes to all green or stays all red. If it stays red, then it's the neckboard (with green signal driving the red circuit over). If it switches to green, then it's the main chassis (with the red signal locked on going to the neckboard)...
 
May not. Replace it and remove the video input connector and check again.

And you can always swap the red and green input wires to where they solder to the neckboard, to see if it changes to all green or stays all red. If it stays red, then it's the neckboard (with green signal driving the red circuit over). If it switches to green, then it's the main chassis (with the red signal locked on going to the neckboard)...

Replace "it" - do you mean the neckboard?

Will try swapping those wires, too.

EDIT: Duh. Replace that connector and remove the sync connector - got it.

Okay, with the sync/input cable off, get the red screen but no picture.

So, that would make it the neckboard since no red with it disconnected but red with it connected, correct?

EDIT 2: Okay. Reflowed all the parts in the red circuit on the neckboard. No change. Swapped the red and green wires over on the neckboard - now it's all green. So, it's the chassis? I think I follow the logic here - the red wire is now actually driving the green signal on the neckboard, so the red signal (now powering the green signal) is overriding the other signals from the chassis. Right?

Guess I'm confused what the removing of the neckboard connector proved then.
 
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Guess I'm confused what the removing of the neckboard connector proved then.

Removing the neckboard connector means that no more signal from the chassis to the neckboard. If you had a shorted red drive transistor or shorted red gun in the tube, it would stay red without a signal.

The fact that it went away means that it needs a signal to make it go all red. Now, removing the video input connector didn't make it go away, so you know the problem isn't with the game board. Swapping the red and green wire on the neckboard made it all green, so now you know the problem isn't on the neckboard, but with the red signal coming from the chassis.

The good news is that there isn't a lot of parts on the main chassis between the red input and the red wire to the neckboard. If you already replaced the two transistors there for the red (and installed them properly) make sure they aren't still shorted. Look for solder bridges. Check the diodes and resistors looking for a short. It's there somewhere...
 
Removing the neckboard connector means that no more signal from the chassis to the neckboard. If you had a shorted red drive transistor or shorted red gun in the tube, it would stay red without a signal.

The fact that it went away means that it needs a signal to make it go all red. Now, removing the video input connector didn't make it go away, so you know the problem isn't with the game board. Swapping the red and green wire on the neckboard made it all green, so now you know the problem isn't on the neckboard, but with the red signal coming from the chassis.

The good news is that there isn't a lot of parts on the main chassis between the red input and the red wire to the neckboard. If you already replaced the two transistors there for the red (and installed them properly) make sure they aren't still shorted. Look for solder bridges. Check the diodes and resistors looking for a short. It's there somewhere...

Ah, okay. Well, good techniques to know but I'd already ruled out the tube and game board with a known good G07 chassis that I have.

Reflowed all the parts in the red circuit, just hoping. No change. Also, triple checked the polarity on all my caps and they are all correct. Grrrr. . .

Gonna have to test 'em now.
 
Found a small bridge on X101 to a resistor on the chassis and thought "I got you!"

Removed it - still red.

Swapped out X101 with X103, thinking that the short fried X101 - still red.

My face/neck - red with anger at this point. :(
 
Do have the capability to do voltage checks on X101 and X102 while the chassis is running? If so, do so and report back the voltages on b-c-e. Try swapping X102 with X104. Check D101. After that go through the 9 resistors on the red circuit there, and compare them to the complements in the green circuit. If everything has been done so far as you said, then it should be one of those parts. Oh, and make sure those transistors aren't in backwards...
 
Oh, and those transistors are on the main chassis. And just for kicks, swap X101 and X102 on the neckboard. test in between each change. If you do it all then test - and have something different - then you won't know what exactly did it.

And just in case none of this helps, try checking R517 and R518 for a short or open. It's not part of the color circuit, but it feeds the +12 to the drive transistors...
 
Do have the capability to do voltage checks on X101 and X102 while the chassis is running? If so, do so and report back the voltages on b-c-e. Try swapping X102 with X104. Check D101. After that go through the 9 resistors on the red circuit there, and compare them to the complements in the green circuit. If everything has been done so far as you said, then it should be one of those parts. Oh, and make sure those transistors aren't in backwards...


Last night, I actually did all of that except for checking the voltages while running. Resistors in tolerance with their counterparts in other circuits, as was d101. Had also swapped the neckboard transistors way back as that was a really simple swap.

Now, in keeping with the cluster this chassis is, the voltage on the big white resistor is indicating deflection failure as it now gives NO picture.

Think it's time to bite the bullet, throw this one to the parts pile and just install the good chassis that I rebuilt some time ago.

Bah.
 
Damn, I am having this exact same problem. It is intermittant right now. When the red centipede turns black the black backgound turns red like your screen. Did all the swapping and nothing. I hope you find the problem and post hear.
 
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