Just curious, would an old ATX power supply from a desktop computer work in this application? Has well regulated 5V and 12V DC. I'm having this same issue in my LW3. The hum was always there but tolerable. I just recently swapped out my old failing power supply with a new Rottendog and now the hum is really bad for some reason.

*** Nevermind! I just noticed this was addressed like ten times already. Gonna give it a shot.

Just to be clear with using an ATX PC power supply for the sound board: aside from plugging in the power supply to a 110AC source and jumping the supply to keep it always ON (which I am aware of how to do), all I would need to do is remove the CN2 sound board connector and connect my sound board's power input to the 5+, 12+, 12-, and GND to the ATX supply wires . It's as simple as that, correct?

Also, why is there a 12+ and 12- but only a 5+? I was always under the impression that with DC current you have a positive supply line and negative was essentially ground. So on a voltmeter, to check voltage would you connect 5+ and GND to check the 5V line, and 12+ to 12- to check the 12V line?

thanks for the info!

One more question, just out of curiosity are any one of those three lines (5+, 12+, 21-) most likely to cause noise/hum if the supply is dirty? If, for example, it was most likely the 5+ line, then in theory could you use a regulated switching 'wall-wart' 5v, 2-amp power supply and connect it's + to the sound board's 5+ and the wall-wart's negative to ground, while leaving the rest of the sound board's 12+ and 12- and GND pin connected to the DE power supply board?

Yet another question Is 22 gauge wire sufficient to run from an ATX supply in the cab up to the sound board?

To anyone interested I did the ATX pc power supply mod (hack).... WOW! So silent in attract mode you could hear a pin drop from a mile away . Seriously, ZERO hum, and sound is crisper and bass seems to be more pronounced. Just beautiful.

I know a lot of people would frown upon this but I ended up rewiring my cab so the power switch under the cab turned the service outlet off and on. I used an ATX power supply for my sound board that draws power from the service outlet, as well as some additional lighting I added to the machine that use switching DC power supplies that plug into a standard AC outlet.

Not to sound like a broken record because this was said before (but lost in the abyss of 500+ previous posts) but the easiest solution seems to be a standalone power supply for the soundboard. Inexpensive and pretty easy to install and cuts out the hum entirely. It did for me anyways.

There were a few links posted miles ago in this thread to power supplies (available on ebay/amazon) that supposedly worked. I used an ATX power supply from an old desktop computer that I had lying around and it worked perfectly. My hum was originally bad, but tolerable as long as there was some other miscellaneous ambient noise in the room. After switching to a Rottendog power supply the freaking hum could be heard from across the street. I used the ATX power supply for the sound and now its silent. I rewired my service outlet so it no longer bypasses the ON/OFF switch under the cab and plugged my ATX into it.

This is probably unrelated but I had horrible hum on a Space Shuttle I picked up last year. Everything worked for the most part except for a faulty wire harness to the display logic. I attributed the hum to worn out caps. I had to remove the MPU/Driver board to replace a bad header pin connector. This required removing every wire harness from the MPU/Driver board. I cleaned all the male header pins with electronics cleaner before plugging the wire harnesses back in. After this the speaker hum vanished. So whatever was causing the hum was apparently from poor wire connectivity, probably from the PF lamps, since the humming would strobe and oscillate in lockstep with the playfield lighting sequence. Lesson here is you may want to check quality of the header pins and wire harnesses elsewhere on the MPU board, displays, etc, in places that would be seemingly unrelated to sound/speakers.

This is old news for this thread but you could always default to a standalone power supply. I used an ATX power supply out of an old desktop computer to power my soundboard and it is literally dead silent, not a peep. The only noise is the quiet hum of the cooling fan coming from the cab, but even in a completely silent room it is only noticeable if you are intentionally trying to hear it.

Holy crap that's loud. I think something else may be wrong with the sound board.