Switching JAMMA Power Supply (interference)

Zak

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Sep 8, 2001
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313
Hi guys,

I recently changed my switcher from a generic Chinese PSU to a Meanwell RT-125A PSU.

It's all working nicely. However, after swapping the PSU, I now have a lot of interference (scrolling diagnal lines).

It's not PCB specific, it will do it with ANY PCB plugged in.

If I disconnect everything from FG on the PSU, then the interference disappears (permanently).

Has anyone experienced this with their switchers?
 

aha2940

AH, A, COLUMBIAN!,
Joined
Dec 15, 2013
Posts
2,528
Hi guys,

I recently changed my switcher from a generic Chinese PSU to a Meanwell RT-125A PSU.

It's all working nicely. However, after swapping the PSU, I now have a lot of interference (scrolling diagnal lines).

It's not PCB specific, it will do it with ANY PCB plugged in.

If I disconnect everything from FG on the PSU, then the interference disappears (permanently).

Has anyone experienced this with their switchers?

I have the same power supply and the only issue I have found with it is that it whines (literally) with boards that use less than 1A (MVS MV1C comes to mind) but it produces no interference at all. How's your wiring? what's FG?
 

Zak

WWJCVDD?,
Joined
Sep 8, 2001
Posts
313
I have the same power supply and the only issue I have found with it is that it whines (literally) with boards that use less than 1A (MVS MV1C comes to mind) but it produces no interference at all. How's your wiring? what's FG?

FG = frame ground (coin chute, cabinet frame etc.)

I have experienced no whining.

I read somewhere that linking FG to common ground will get rid of the interference.

Disconnecting coin, frame etc. from FG on the PSU fixed my issue - just wondering if there are any negative effects of doing this?
 

aha2940

AH, A, COLUMBIAN!,
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Dec 15, 2013
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FG = frame ground (coin chute, cabinet frame etc.)

I have experienced no whining.

I read somewhere that linking FG to common ground will get rid of the interference.

Disconnecting coin, frame etc. from FG on the PSU fixed my issue - just wondering if there are any negative effects of doing this?

AFAIK, all the parts of the circuit should use the same ground to avoid having ground loops, which lead to interference. Maybe that's what you were having.
 

skate323k137

Professional College Dropout
10 Year Member
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Jan 7, 2013
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4,186
Bridge DC ground and FG. I've had the same issue on every Happ psu I've ever owned.
 
Last edited:

Zak

WWJCVDD?,
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Sep 8, 2001
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313
So a wire from Common to FG like this?

JSkHI3P.jpg
 

Zak

WWJCVDD?,
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Posts
313
Do you have any idea why this happens on some PSUs?
 

skate323k137

Professional College Dropout
10 Year Member
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Jan 7, 2013
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Basically a ground loop causing interference. The only PSUs that I never had the problem with already make this connection internally.
 

Zak

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Sep 8, 2001
Posts
313
skate, you're a friggin' hero! :) It's working nicely (Common to FG).
 

Kid Panda

The Chinese Kid
Joined
Jun 13, 2010
Posts
12,514
Yea when I switched out the PSU in one of my candies I had the exact problem. Most likely due to most candies having no ground on the wall plug.
 
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