New 8liners monitor - headaches

[jimbodeanny]

The 4500 had all kinds of issues. None of the adjustments seemed to do anything, and the convergence was way off. The tube also had massive burn in. It was a mess. That's what made me decide that I wanted to replace the monitor.

http://forums.arcade-museum.com/showthread.php?t=128644

 

[KenLayton]

Isn't Frogger a positive sync game? If so, the Wei-ya chassis is designed for negative sync only.

Frogger is a game that doesn't like some monitors. It seems the monitors that worked best in it were Nanao MC-2000-S, Electrohome G07, and Wells-Gardner k4600.

Keep in mind also that during the production run of Frogger, Sega-Gremlin used some two dozen different makes and models of monitors (mostly Japanese brands) to keep up production quotas. In many cabinets (but not all) the isolation transformer had two different voltage outputs: 100 volts for Japanese monitors like Nanao and Toei, and 120 volts for American monitors. Double check the AC voltage going to your monitor's power connector.

What model of Wei-ya chassis is this again? Some are 120 volts isolated AC only and others are 90 to 240 volts non-isolated.

 

[jimbodeanny]

Isn't Frogger a positive sync game? If so, the Wei-ya chassis is designed for negative sync only.

Frogger is a game that doesn't like some monitors. It seems the monitors that worked best in it were Nanao MC-2000-S, Electrohome G07, and Wells-Gardner k4600.

Keep in mind also that during the production run of Frogger, Sega-Gremlin used some two dozen different makes and models of monitors (mostly Japanese brands) to keep up production quotas. In many cabinets (but not all) the isolation transformer had two different voltage outputs: 100 volts for Japanese monitors like Nanao and Toei, and 120 volts for American monitors. Double check the AC voltage going to your monitor's power connector.

What model of Wei-ya chassis is this again? Some are 120 volts isolated AC only and others are 90 to 240 volts non-isolated.

I'm looking at the manual right now...how do I tell if the game uses positive or negative sync? I assume that if you're correct, Ken, and the game uses positive and the monitor uses negative, that this would be the source of the problems?

When I get home from work, I'll check the voltage coming off of the isolation transformer and also check what model of chassis I have.

Thanks for the help, Ken!

 

[RetroHacker]

Many monitors simply won't sync if the signal is wrong (positive vs. negative). This one locks in on the sync, but as you notice, the picture is distorted. I can see how this could happen. I was not aware that Frogger was positive sync, having never worked on one.

Try the new monitor with a different game, one that uses negative sync. If that works, then all you need to do is rig up a sync inverter for your Frogger and you should be set.

-Ian

 

[jimbodeanny]

Try the new monitor with a different game, one that uses negative sync. If that works, then all you need to do is rig up a sync inverter for your Frogger and you should be set.

-Ian

As far as creating a sync inverter, I came across this: http://www.twobits.com/RGB/sync.html

I'm a little confused. Does this chip attach to the game PCB or where do I put it? Also, I know pin 2 is the neg sync that goes to the monitor and pin 1 is the positive sync coming from the game PCB. Where does the +5v and ground come from?

Also, I can't seem to find one of these 7404 ICs on radio shack's web site. Is there a different part number for it?

Thanks!

-Jim

 

[RetroHacker]

I'm a little confused. Does this chip attach to the game PCB or where do I put it?

You can hook it up anywhere. You can hack it right onto the game board by piggybacking it onto another logic chip, you can wire it in-line, whatever. When I have to do this, I usually mount it on a little scrap of perf-board and wire it into the video harness.

Also, I know pin 2 is the neg sync that goes to the monitor and pin 1 is the positive sync coming from the game PCB.

That little picture gives you very little to go on - look up the pinout of the 7404 itself. It's an inverter chip. Six inverters in one package. The inverter takes an input and inverts it - a logic 1 in comes out as a logic 0 and vice versa. For a game that takes seperate horizontal and vertical syncs, you can invert each sync separately using two of the inverters in the package, and send them separately to the monitor.

Where does the +5v and ground come from?

From the power supply in the game.

Also, I can't seem to find one of these 7404 ICs on radio shack's web site. Is there a different part number for it?

The 7404 is available in many logic families. Try 74LS04. Something tells me Radio Shack no longer carries them, seeming as though it's not a cell phone. It's a very, very common logic chip, any real electonic supplier has them, and you should also be able to scavenge one off a junk board.

-Ian