SOLVED - 5 pin arcade monitor sync problem

[steve612]

Hello everyone,

A friend of mine found an arcade that has Pocket gal bootleg on it. It was in storage for a lot of years and we decided to restore it a little bit. It is in very nice shape. I decided to put a new jamma harness on it. I discovered that the sync from the monitor has 2 cables, one HS and one VS. For pocket gal those 2 cables were connected together when we opened the cabinet, and the game was running ok. I did the new wiring(new jamma harness) and i connected HS and VS together as it was. Now when i power up the game sometimes it has sync issues, and sometimes starts normally. That happened and before.
I decided to test another game in this cabinet, the game was running ok(sound credits, controls etc), but the picture was messed up. Sync issues. I switched on and off the cabinet, with no luck(as the other game). I searched on the internet and i found that there is a chip LM1881 that separates the signal from csync to hs and vs(i think). The circuit has also some resistors and capacitors. I am not sure if this will solve my problem, please help me.

Thanks a lot!

[Rigby]

Make sure your sync cables are connected together well.  If there are intermittent disconnections there you'll have the issues you speak of.

[steve612]

Cables are connected well, i used a soldering iron to be sure that everything is ok!

[Rigby]

Ok.  Time to start checking other solder joints for problems.  If you're bored or really want this fixed right now I would pull the chassis out of the monitor and re-melt every last solder joint you can find.  Over time the heat-cool cycle will break the solder joints and cause intermittent issues, and re-melting the solder fixes that.  If you want to be thorough, wick away all the solder that is there and lay new solder down, one by one.

Make sure they're all good by either resoldering them or remelting all the solder that's already there.

The first pic in the post here http://forums.arcade-museum.com/showthread.php?t=134818 shows what a cold solder joint looks like.  Find those, fix them, and let us know if that helps.

[steve612]

There is some irony. I didn't mention that I installed a cap-kit to the chassis. I took a quick look at the joints and i thought everything seemed to be ok. I don't know, maybe I will take another look. Is it normal for a monitor to have HS and VS and short them together? There is also 2 switches on the chassis that say positive or negative for each HS and VS. What are these? Thanks for you help

[Rigby]

Is it normal for a monitor to have HS and VS and short them together? There is also 2 switches on the chassis that say positive or negative for each HS and VS. What are these? Thanks for you help

Usually they are combined, but the PROPER way to do it is not to short them together but to use a TTL logic chip to join the two and to convert from Pos to Neg or Neg to Pos.  Shorting works, though.

Most arcade chassis use negative combined sync.

[steve612]

I found the solution! H hold was not in the center and i put it in the center and that fixed the problem!
I found it from Bob Roberts! http://www.therealbobroberts.net/slanted.html

I hope this will help others too!