So I have an M-200 MPU in my Star Gazer that doesn't always reset/boot reliably when I power the game on.
It works fine about 2/3rds of the time. When it fails the MPU has a solid LED. Pretty sure it's not resetting consistently.
I power up my games with a wall switch that turns on the plug circuits. Often Star Gazer won't reset when the wall switch is turned on and I'll have to use the cabinet switch to power it off and on again. It almost always boots fine when I do this.
I completely rebuilt the reset section on this board after repairing alkaline damage on it a few years ago, so every component is newish.
I also saw a tip on http://techniek.flipperwinkel.nl/ballyss/rep/index2.htm#flash to use a capacitor to make flaky reset circuits more reliable:
"It could be the +5 volts is not stablizing within the "window" the CPU expects (about 50ms). To make the reset window longer, try putting a 470 mfd electrolytic capactor in the reset section (on the solder side of the MPU board). Solder the positive leg of this cap to the collector (top leg) of Q1. Then solder the negative leg of the cap to ground (the emitter of Q1). This will increase the reset timing length. Now test the MPU board. If the MPU board works and continues with the flashes, the +5 volts was just not getting "stable" in the 50ms window (there could be a power supply problem, probably with the large 5 volt rectifying capacitor on the driver board). "
I tried adding a 470uf cap as described but it made it worse. In fact it only booted once in about 10 tries with the cap installed. So I removed the cap and now I'm back to it booting about 2/3rds of the time with the wall switch.
Oh, the powerboard is using one of those new fangled solid-state voltage regulators also (voltages are fine once things are booted).
Any thoughts or suggestions?