my G07 - what went wrong?

vintagegamer

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I have a Ms. Pac that when I got it had damage to the neck of the tube. However the neckboard and monitor chassis, were, I believe, OK. When you powered up the machine with the neckboard unattached to the tube, you would hear a "buzz" sound, which I figured meant it was getting power.

I initially tried to repair the original tube by reattaching the white plastic piece to the base of it that slips over the pins (it had come off somehow by the prior owner's work). I hooked up the neckboard to the tube and on power up, could see a blue spark-like light, different from the orange you would see with a tube that is OK. After about 10 secs the spark-like light stopped.

I have since gotten a newer tube, installed it and hooked everything up. But this time, I am getting nothing at all. Does it sound like I damaged the monitor chassis by hooking it up to the broken tube? Here are some other things I have already checked:

1. there is 125V AC getting to the monitor chassis, checked that with my multimeter
2. The fuse that is lowest on the chassis board when the board is mounted in place is OK. I did not remove the chassis, I only fed my continuity tester up to it to see if it beeped. It did.

Please tell me what to check next. I keep hearing in the back of my head, "you fried your flyback". I hope that voice is wrong. :(

VG
 
If the only tool you have is a multimeter you should check the B+ in accordance with the manual. You can also test the flyback coils for continuity. I believe there is a second fuse as well, have you tested it?
 
Oh, and what G07 chassis do you have?

The kind that works in a Ms. Pac :p Hell I don't know, it just reads "G07 CB0" on the side. Do you need the number on the actual chassis board?

I guess I should have just bought that other monitor chassis from you and called it a day. But I wanted to learn more about these damm things. Sonofa.......
 
No, G07 CB0 is good enough. Do you have a CBO manual or access to one online? The computer I am currently posting from is still experiencing "technical difficulties" with .pdf files...
 
Actually at this point before doing a full-scale rebuild, I'm trying to identify what might have happened, or do some further tests. Can I pull the neckboard and do a voltage check there somehow with the multimeter while the unit is on?

It just seems odd that the monitor chassis would have survived years of neglect, survived the tube damage, work when being hooked up to a broken tube, and then decide to puke when a good tube is put in :(
 
Yeah, that is why I suggested you check the B+, this is the voltage that gets stepped up to power the tube via the flyback. You can check for power on the neckboard as well but without B+ the flyback can't generate the high voltage to create a picture.
 
Yeah, that is why I suggested you check the B+, this is the voltage that gets stepped up to power the tube via the flyback. You can check for power on the neckboard as well but without B+ the flyback can't generate the high voltage to create a picture.

What is needed to check the B+ voltage?
 
here's a link from bob roberts, jim.
go7-1.jpg
 
If you give up on it send it over and I will check it out for you.
Are you getting neck glow at all? If you left it on for any length of time its possible the hot was toasted. If you still have neck glow your HV should be good other than a possible adjustment. Even then, you should have something coming up on the screen.
How about the two fuses, checked those yet?
 
If you give up on it send it over and I will check it out for you.
Are you getting neck glow at all? If you left it on for any length of time its possible the hot was toasted. If you still have neck glow your HV should be good other than a possible adjustment. Even then, you should have something coming up on the screen.
How about the two fuses, checked those yet?


I checked the one I could get to (the chassis is still in the game, I didn't get enough time to pull it out of the cab yet). It was OK. It was the one just to the left of the B+ adjust shown in the Bob Roberts pic.

I am not getting any neck glow at all.
 
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