Galaga PCB Rolling

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Hello,

Ive had this Galaga machine working for about 3 years now. It has been converted to a switching power supply and has had no issues in the past.

However, the game is rolling now.

THIS IS NOT A MONITOR ISSUE.. I have plugged in a test pattern generator to the monitor and it looks great.

The problem is located on the pcb or power supply. No wiring has changed. It just started rolling all of a sudden.

What should I check?

Thanks for your time.

Here's a video link

https://youtu.be/yqCVJdYp7zY
 
Hello,

Ive had this Galaga machine working for about 3 years now. It has been converted to a switching power supply and has had no issues in the past.

However, the game is rolling now.

THIS IS NOT A MONITOR ISSUE.. I have plugged in a test pattern generator to the monitor and it looks great.

The problem is located on the pcb or power supply. No wiring has changed. It just started rolling all of a sudden.

What should I check?

Thanks for your time.

Here's a video link

https://youtu.be/yqCVJdYp7zY


If you have a scope, I would look at 1N pin 17 on the Video Board.

If you don't have a scope, you could try (very carefully) re-seating the Custom. Be careful as the legs on those are very brittle and can break off easily.
 
Last edited:
Have you adjusted the V-hold on the monitor? I know you state the TPG works, but he sync from the PCB could be slightly different. It's worth a try anyway.
I have had this problem 2 times. One on a Centipede and one on Ms Pacman. One of them was a bad connection between the video input from the harness to the monitor chassis (dirty causing crap connection) and the other was a bad V-hold pot, the resistive element had burned and cracked right where the wiper had been set forever ago.
 
Have you adjusted the V-hold on the monitor? I know you state the TPG works, but he sync from the PCB could be slightly different. It's worth a try anyway.

This.

Not all boards/test fixtures output exactly the same frequencies. As a matter of fact several of the same boards can output differently, these things are 30+ years old after all.

The way that screen "bounces" makes me think that vertical hold is your issue.
 
echoing other opinions, the vertical hold is just barely off. test its extremes back and forth to see where it rolls, then set it as close in the middle between them as you can.

additionally, verify that your switcher voltages are correct. a friend's switcher lost its voltage adjustment and shot 5.93V into the board, nuking the rams. 5.20-5.25 at the power supply should be more than sufficient barring loss. there's several capacitors on the CPU board that are due for replacements, I would look into that as well.
 
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