Hi all @ Pinside,
My 1989 System 11B #Mousin' Around! is experiencing weird power issues.
All is well initially upon power up but after being on in attract mode or being played for about an hour it starts to shut itself down.
The first obvious issue is that I slowly start losing digits on both displays. They fade away in pairs, both left and right, until only four, two on each side, are illuminated.
As the digits are fading from the displays I also start losing brightness to the controlled playfield lamps until they fade and go out. Only the controlled "millions" on the back insert and "mouse" on the playfield remain faintly lit. GI remains unaffected.
I lose power to the flippers, and eventually one of the three relays will start buzzing badly. This is usually when I turn it off.
It takes about 10 minutes for this power issue to eventually shut the machine down.
The CPU is running fine and I can start a game, but the solenoids slowly become weak and eventually stop working. For example, the coil becomes too weak to kick the ball into the shooting lane though it tries.
If I turn it back on I get five "bong" tones and only four digits on the displays. Only GI is illuminated. If I work my way through the menu in the blind I can usually get it to go into attract mode but there is only GI and a few digits on the display working.
Power supply voltage at the test points is correct, as well as 5V on the MPU test point.
I replaced all electrolytics on the power supply board and replaced 6BR1. I've checked every connector, fuse, reflowed pins, etc, to no avail.
I can usually turn it on in a day or two and all will be fine. Maybe. But within an hour it will go through the slow "power down" cycle again.
What the heck is going on???