PSU losing power over time? (CPS2 Darksoft cabinet)

[USSCrazybat]

Hi all,

Ran into a bit of a strange issue. Our cabinet that we have on location wasn't booting (currently running a CPS2 Darksoft kit). When I finally got into the guts of the machine, the voltometer attached to the edge connector was reading 4.2v. After attempting to manually adjust, the pot on the PSU maxed out at 4.6v. The game appeared to run stable at 4.4.

(Some information about the use of the components. The last time I had adjusted the voltage was after the installation of the CPS2 board at which time I set it to 4.9/5.0v. This was nearly a year ago. Both the power supply and CPS2 kit have been in use for several years. PSU for approximately five years and CPS2 for approximately two in total, Monday to Saturday, 10am - 5pm. Currently connected to the jamma harness is:
CPS2 Board (with worn down fan, buzzing on startup - could this be adding interference some how?)
LED Strip for marquee (5v, also as old as the PSU)
12v coin mech
GBS-Control (using 5v)
1 basic speaker

The PSU and LCD monitor are both connected to a surge protector inside the machine which plugs into the wall.

I've since adjusted the PSU back down to 4.3, and will be returning in the morning with all the equipment I have. I currently don't have a replacement PSU (and with AWUK going apeshit, I'll probably have to go to another supplier.) I am hesitant to leave the PSU any higher than it was originally for fear of it righting itself and frying the board with an excess of voltage. Is there anything I haven't considered besides getting a new PSU? The surge protector could be a possible point of failure, but I don't have enough equipment to test at the moment. Any insight would be appreciated, I do not want to fry my £500 kit!

 

[TheDaddy]

Surge protector will not limit any voltage at all so I would rule that out myself. I would suggest a replacement PSU , Or at least check this first. Other option is to take the board out and test in a different rig but its rare a board fails and runs whilst sucking voltage down. You may find when its cold the voltages will be ok and then as the caps start getting hot voltage will drop.

Oh and replace the whining fan as well , At some point will stop and board will overheat !

Dave.

 

[qjuk]

Ignore the voltmeter reading for the moment and get a DMM (digital multimeter), measure the voltages at both the PSU and the edge connector. What is the difference (drop) in voltage between these two points?

I’m inclined to think you’ve either got worn edge connector pins or your wiring needs looking at (especially after years of constant use). It could be the GND wiring near the edge connector is perhaps going a bit brittle and needs renewing.

I have known PSU’s to drift in voltage after a while (usually the cheap Chinese ones), so if you do replace your PSU, I’d certainly recommend to spend a bit more and fit a decent branded one.

 

[USSCrazybat]

Thanks for the feedback. Didn't have time for a lot of experimentation or testing yesterday, so just did a quick boardswap with a Namco System 11 (Tekken 2) to check some things out. Immediately things went back to normal - I'd lowered the voltage to 4.2 before removing the CPS2 board, and once I plugged T2 in I got 4.8. Obv CPS2 is far more power hungry but this was far more stable than I was expecting. Once I plugged the CPS2 back in, I got a stable 5.0 upon adjustment, and everything seemed to be fixed? I have no idea what's happened, unless there was corrosion on the edge connector that was knocked loose or something.