Rally X audio hum and video hum bars

TheShanMan

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Donor 2011, 2024
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I'm thinking of getting a Bob Roberts 90411 power supply rebuild kit (it says it can be used on 90414 boards) to fix this bad audio hum and hum bars on the monitor. Think the problem could lie elsewhere? I'd rather order everything I might need and get it done and over with. The monitor (g07) has been recapped btw.

You can hear the audio hum as well as see the hum bars by watching this quick vid. Both problems are pretty bad so you won't have any trouble recognizing the problems.

 
The Galaga that I had at the NW Pinball show did that the first year that we took it down there. The rebuild kit will fix that problem. The only other thing that wouldn't hurt to get is an AC line filter.
 
I did most of the rebuild kit. I did not replace the regulators, transistor, pot, or IC. I figured if they're currently working, they probably don't need replacing, possible exception being the pot. I did replace all caps and diodes. I also replaced the power headers, pins, and housing (I have replacement headers, pins, and housing for the connections to the main pcb, but haven't done it yet).

Video is perfect now, and most of the audio hum is gone as well. Some remains however, and it is very specific to what is on screen (i.e. the hum changes very noticeably when it changes from an "instructions" screen to a "demo" screen, for instance). I have noticed this type of hum on other games too so I know it's a common thing. But before I keep pouring time into the power supply, I figured it's worth asking "what usually causes this kind of hum?" My hunch is caps on the game pcbs, not something on the ps pcb, but I'd appreciate feedback from the experts.

I did buy a line filter but before spending time getting that integrated into the system, I'm interested to hear what kind of problems line filters commonly solve, or at least whether it's a good possibility that it would solve my remaining problem.

Frankly I can live with it as this game might not even be a long term keeper, but eventually it would be nice to completely fix it.
 
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