G07-CBO high B+ and bad curl

SUSPENCE13

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Alright so I have two problems with my G07 in my Pac Man.

1. My B+ lowest adjustment is 148 volts but I should be able to bring this down to 120 volts but I bottom out the pot and the lowest it goes is 148 volts. Im wondering if my problem could be the voltage going to the monitor from the isolation transformer. When I measured the AC voltage coming out of the transformer to the monitor I was reading 170 volts. Could that be too high?

2. My other problem is a bad curl at the top right of the monitor and a little bit of a curl at the bottom right. So far I have done a full deluxe cap kit from Ian and I did the mod that is suppose to help with the curl on these monitors. I have adjusted every pot on this monitor for hours with no good results.

I appreciate any help
Thanks.
 

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Did you use a 22uf cap up in C303 for the curl mod, or a 10uf cap? In my experience the 22uf helps eliminate the curl much better.

170vac does seem high.

It is possible the B+ issue is leading to your other problem. You are measuring DC voltage?

A quick look at your first pic makes me think you have the original flyback still. I would change that (as a common practice on g07's).

I know I've had a high b+ Issue like this before, I need to see if I documented it anywhere. May have been a flyback, or bad r908 or r912.
 
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Yes, I used a 22uf 50volt cap

Yes, I am measuring with DC voltage

I still have an original flyback I didn't change that because Ian was out of stock

I replaced R908 but I didn't replace R912

So the flyback is probably where I should start I'm assuming and maybe replace the R912?
 
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Yes, I used a 22uf 50volt cap

Yes, I am measuring with DC voltage

I still have an original flyback I didn't change that because Ian was out of stock

I replaced R908 but I didn't replace R912

So the flyback is probably where I should start I'm assuming and maybe replace the R912?

I just say flyback as a rule, not the cause of this problem (necessarily). Yeah test R912 for kicks.

You could test the b+ pot as well.

I think the first thing may be to test that entire monitor in another cab that has a lower AC voltage coming from the isolation transformer and then measure your b+.
 
that thing looks like you could eat off it.

does your monitor plug have the negative syncs bridges between the horizontal and vertical pins? I've run tons of JAMMA games with these and never had issues with curling, never modified that, but I did have to bridge the syncs. the factory Pac-Man harness actually has it run like that, probably for these monitors specifically. it won't hurt the 4600 or 4900 at all.

isn't X701 the voltage regulator? usually like any monitor that hits 170V it's a bad VR. do G07s not have shutdowns?
 
X701 is in the shut down circuit. If it is removed the monitor will operate even if the voltage reaches the shutoff point. Usually a GO7 will shut down at 135 Volts I believe if the shut down circuit is working correctly.

X04 is the power regulator.
 
Where are you measuring your B+ at? You should be measuring it at R01. Ceramic resistor mounted to the side of the chassis. One side will be around 145 volts while the other side will be your B+ and should adjust to 120 volts. Normally no more then 125 volts If not most likely X01 is shorted. If your B+ is that high and X701 isn't removed then there is also a problem in the shut down circuit.
 
X701 is in the shut down circuit. If it is removed the monitor will operate even if the voltage reaches the shutoff point. Usually a GO7 will shut down at 135 Volts I believe if the shut down circuit is working correctly.

X04 is the power regulator.

doh. had it backwards in my head. :(

thanks for the info. Ed West knows a lot of stuff.
 
I have been checking the B+ off the ceramic resistor on the end closest to the tube and sometime this week I'm going to double check the X01 to see if thats shorted.

Thank you for all the help.
 
x01 is not shorted or you wouldn't have a picture.

If you are testing that resistor on the far point (closest to the tube), vs closer to the adjustment pots of the chassis, you are doing it correctly.


Yeah here is the link to when I had a similar problem awhile back:
https://forums.arcade-museum.com/showthread.php?t=387375&highlight=g07+high

My problem turned out to be R908. I always test them before I install the new R908. I highly doubt Ian sent you one out of spec, but if you really start to hit a brick wall, everything is in play as a potential problem.
 
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Alright got it fixed and I feel stupid not realizing it but my multimeter was low battery so it was reading my B+ voltage high when it was really reading 100 volts. Adjusted it to 120 volts and everything is looking really good. Glad it was simple at least.

Thanks for all the help
 
Well that was an easy fix.

X01 can be shorted from collector to emitter and still have a picture if X701 is removed or there is a problem with the HV shutdown circuit. I know because I have seen that situation.
Operators wanting to get a game running no matter what. They would have X701 removed. Then when they were slow or closed they would then have the chassis repaired. Again I know because I did it a couple of times. Then I started stocking spares part for just this situation.

Ed
 
Well that was an easy fix.

X01 can be shorted from collector to emitter and still have a picture if X701 is removed or there is a problem with the HV shutdown circuit. I know because I have seen that situation.
Operators wanting to get a game running no matter what. They would have X701 removed. Then when they were slow or closed they would then have the chassis repaired. Again I know because I did it a couple of times. Then I started stocking spares part for just this situation.

Ed

I've seen the VR bad a lot and had the chassis still work, but never the HOT. Clearly I have only seen 1/10th of the chassis' you have though. (or less)
 
Sorry had a senior moment. Should have been X04 not X01. Yes if the HOT is shorted it won"t work.

Sometimes fingers work faster then the mind.

Ed
 
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