Hi, I'm working on a Sanwa PM1723C which loses V-hold when it has been running about 20 minutes.
It all starts out ok, but after 5-10 minutes the image start to twitch a bit. And after 15 minutes the image starts to roll vertically.
After 20 minutes it rolls so fast that I cant distinguish any graphics on screen.
I've checked all solder joints around the HA11235 sync IC.
I've replaced the V-hold pot
All caps have been replaced.
I've also socketed the HA11235 sync IC and replaced it with a known working one.
No difference at all.
Any pointers at what to look for?
I'm going to buy one of those air-in-a-can so that I can flip it upside down and shoot some ice cold air onto some areas of the chassis handling vertical sync.
I attached the schematics for this chassis as well.
Thanks
Sanwa PM1723C, loses V-hold when warm
- frsj8112
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Sanwa PM1723C, loses V-hold when warm
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- grantspain
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Re: Sanwa PM1723C, loses V-hold when warm
could be a diode or transistor breaking down, is it in the sync or hold circuit is the question
- frsj8112
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Re: Sanwa PM1723C, loses V-hold when warm
Update!
I've found the problem.
This chassis has been put aside, I've taken a look at it and put aside again.
But now I had some spare time again and started to go over it again with the freeze spray.
Found that in the area around the H-size coil I could get the vertical rolling to almost go away, see video
I then sprayed this capacitor, C320, which some previous owner had replaced with a tantalum capacitor instead of an electrolytic. I had found the issue. When spraying this the rolling effect went away.
The tantalum had the correct specification, 47uF 20V (original was a 47uF 16V electrolytic) and I measured both ESR and capacitance and it checked out OK.
I replaced it anyways with an electrolytic capacitor, 47uF 50V and heres the result after having the monitor running for about 2 hours:
And here's that tantalum that desoldered: Happy days
I've found the problem.
This chassis has been put aside, I've taken a look at it and put aside again.
But now I had some spare time again and started to go over it again with the freeze spray.
Found that in the area around the H-size coil I could get the vertical rolling to almost go away, see video
I then sprayed this capacitor, C320, which some previous owner had replaced with a tantalum capacitor instead of an electrolytic. I had found the issue. When spraying this the rolling effect went away.
The tantalum had the correct specification, 47uF 20V (original was a 47uF 16V electrolytic) and I measured both ESR and capacitance and it checked out OK.
I replaced it anyways with an electrolytic capacitor, 47uF 50V and heres the result after having the monitor running for about 2 hours:
And here's that tantalum that desoldered: Happy days
You do not have the required permissions to view the files attached to this post.
- ChrisBEANS
- moneyspendingexpert.com
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Re: Sanwa PM1723C, loses V-hold when warm
I have no idea what half of that meant, but congrats dude, glad it’s sorted
- grantspain
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Re: Sanwa PM1723C, loses V-hold when warm
yeah good work, again someones previous repair causing problems- i see this sort of thing all the time