From Tom Wisnionski:
Depending on how 'marginal' the MCR set is, you can tie [Vbatt] to +5, out of 10 Trons sets, this worked for 3 of them. A more correct way of doing it is to create an RC Network with a 1uf Cap, 1K Resistor and a 1n4001 Diode. Connect the gnd of the cap to gnd, The cap + to the reset line, Then parallel the diode and the resistor, now connect the banded end to +5 and the other to the reset line with the cap. This will give you enough reset delay for the boardset.
Things to Note: MCR's are real picky about supply voltage, you will have to mess with the switchers pot to get it to come up. Too high, and she will not come up, it will appear as though its resetting. To, low. and nothing... I think its best around 4.9vdc ish. Again depends on the boardset.
Connect the V+Batt to +5, if it is not connected the Cmos never clears, and the board will not boot.
Thats it, once you get it right, the bugger is alot more stable.
A quick diag note, if you have an MCR supply that you think is the causing a problem, remove Q201, this is part of the POReset line on the analog supply, 9 out of 10 games worked fine after this was removed, again depends on the margins of the boardset, but its a quick fix...
In my experience, switching power supplies cause a lot of speaker hum in the MCR games. This is because switching power supplies generally have lots of noise on the voltage lines. Also, the later version MCR power supply boards have cleaner audio that the older versions, so if you have a choice, get the later revisions (C or D).
Original MCR power supply backup batteries by now have begun to leak, or are at the end of their life. Either way, REMOVE THEM FROM THE POWER SUPPLY BOARD NOW! Then, go somewhere and buy a cordless phone battery which is 3.6VDC. The type that looks like 3 AA batteries wrapped together should work great, and anything rated 600mh or 300mh should be fine. Now, the + and - on the boardset are screened, and the battery should have a red and a black wire. Cut off the connector for the battery, and connect the red to the +, and the black to the other. Now, follow the traces from where you connected the battery all the way to the plug in connector. Test these points with your voltmeter; the voltage should be around 3.6VDC. Now, hook up the PS again and leave your game on for about 14 hours to give the battery a good charge. Your High Scores should once again be saved next time you turn the game on.
Tom Wisnionski has an MCR switcher adapter. It allows you to add a switching power supply to your cabinet without modifying any existing hardware.MCR Power supply manual scans and text(requires Acrobat)