G07... It's really blue.

[Witchboard]

I don't know why these monitor repairs have to frustrate me so.

[Ken Layton]

When you did the capkit, did you do the sync mod also (it eliminates curl)?

It is common after doing the capkit to need to readjust the screen (brightness) control and sometimes the color pots on the neckboard. If adjusting those don't help then you should connect the picture tube to a rejuvenator and test it.

[Witchboard]

I'm pretty sure I did the sync mod.  To tell you the truth, I've been doing so many G07's lately, I can't remember.  I'll double check it.

The screen brightness is all the way down.  I got the typical lines you see when it is too high and I had to crank it until it stopped to get the picture you see.  I've played with all the color pots and none seemed to do anything, excpet the blue one which made it more blue.  I don't have a rejuvenator... but I do have another tube I can use.

[Witchboard]

Well, I double checked to make sure the sync mod was performed and it has been.  I also connected it to another tube and another game and it's still blue.  That eliminates the tube and the game that I was using earlier.  I also switched around the trasistors in the color circuits and it didn't change anything.  I think the curl is caused by a bad coil.  I'll replace it after I figure out the color problem.  Any suggestions on where to go from here?

[Ken Layton]

Remember that resistors R314 and R317 (in the sync circuit) need to be checked for the correct value. The factory mistakenly put in the wrong value resistors in these locations on some chassis. Both should be 390 ohms, but the factory put in 4.7 k resistors by mistake. Transistors X105 (2SC454)and X106 (2SA673) on the main board are the blue color preamp transistors.

[Witchboard]

Remember that resistors R314 and R317 (in the sync circuit) need to be checked for the correct value. The factory mistakenly put in the wrong value resistors in these locations on some chassis. Both should be 390 ohms, but the factory put in 4.7 k resistors by mistake. Transistors X105 (2SC454)and X106 (2SA673) on the main board are the blue color preamp transistors.

I'll check the resistors.  Thanks for the tip.  X105 and X106 are what I've already eliminated by swapping with the other color circuits.  I pretty much moved 101 to 103 and 103 to 105 and 105 to 101... etc.  I was thinking that if it was one of the transistors that it would change the color if they were the problem.  I also swapped x102, 104 and 106 the same way.  Is my logic faulty in thinking this?

[Ken Layton]

Did you swap the color output transistors on the neckboard?

[Witchboard]

Yes.  I guess it's possible that more than one transistor is bad and I just swapped a bad one for a bad one.  They probably aren't that expensive, maybe I'll just replace them all with new ones to be sure that isn't the problem.

[clanggedin]

***Thread Hijack***

What's the sync mod? I have a G07 that needs cap kit kit and the H Sync is extremely sensitive on it. Will the symc mod correct this problem too??

Ken, Can you provide me with a link to the sync mod??

*** End of Thread Hijack ***

[Witchboard]

What's the sync mod?

http://homearcade.org/BBBB/g07notes.html

[Ken Layton]

See my above post about the incorrect resistors being inserted at the factory in the sync circuit.

[Witchboard]

I checked the resistors and in fact one was incorrect.  I replaced it with a correct one, but the issue still remains.    So frustrating.

[Witchboard]

Well, figured I would update this.  I didn't realize that there were two sets of transistors on the main board that needed to be check.  I did the "move one to the left" technique and that still didn't change anything.  I started messing around and noticed that when I turned the red pot on the neckboard nothing changed, where as if I did the blue and green it would bet more blue or more green.  Got out the trusty ohm meter and sure enough, the pot was dead.  I robbed one off another neckboard and replaced it.  Still no change though now I can at least see red in the image.  It seems that everything is turned down.  The screen voltage is all the way down and if I turn up any of the color pots the colors start to bleed.. and it's still blue.

I guess I'll start checking a few other things.  I'm going to fix this monitor if it's the last thing I do.  I will be victorious! 

[Karetaker]

Well for the blue problem it sounds like you swapped out X101. You should also change X105 & X106 on the main chassis board. If it still comes up blue I would make sure that you don't have a shorted gun. You can find out if the gun is shorted by removing the blue transistor X101. If the screen is still blue with the transistor removed, you have a shorted gun.

[Witchboard]

Well for the blue problem it sounds like you swapped out X101. You should also change X105 & X106 on the main chassis board. If it still comes up blue I would make sure that you don't have a shorted gun. You can find out if the gun is shorted by removing the blue transistor X101. If the screen is still blue with the transistor removed, you have a shorted gun.

I swapped all transistors, not with new ones, but with others in their same group.  The guns are located inside the tube correct?  I used a different tube and have the same results.

[Karetaker]

Yes, the guns are in the tube. If you swapped it out then it sounds like it's in the board. I apologize, as I didn't see the part about swapping the transistors the first time I read though it. If someone else was working on this I would make sure no solders are touching something that they shouldn't be. I found that on a board someone had worked on before I got it. I was ripping my hair out trying to figure out what was wrong. Everything tested good, and yet I still had a red screen. Solder Blob! Being a G07 it probably wouldn't hurt to go over the solders anyway. I'm assuming you tested all the resistors in that circuit? Is D103 good? I would just make a copy of the schematic and take a highlighter and start check and marking off everything in that circuit. There's just not that many components in it, so it wouldn't take too long to go through it.

[Witchboard]

It's no problem.  I need all the help I can get.  If that means saying what I've already said over and over.. I really don't mind.    It's a good idea to just start working through the circuit.  I've kind of put this on the back burner since I'm crossing the finish line on my Donkey Kong restoration.  I'll check all the components you mentioned and see if I can wrap this guy up once and for all.  Thanks for the tips.

[bjk7382]

When you did the capkit, did you do the sync mod also (it eliminates curl)?

Is there anything like this available for the wells gardner 4900 series monitors. I have one with a curl on the left edge of the screen. It curls up and down slowly as it heats up. I can't really figure it out, since I already did a cap kit on it.