G20 Possible Power Distribution Issue

[Ash100]

I just received a G20 MLD recently and started the build up process on it and am having some minor issues.


I received the machine in pieces basically, all Boot Chips and Loaders/License Dongles in a plastic baggie, Power Supplies all disconnected as well as the MPU.


I got everything assembled, Bios Chips installed etc. but noticed as soon as I plug in the 110 VAC power cord to the outlet, my service light just blinks. It's a steady bright to dim in 1 second intervals. Almost like I'm getting dirty unregulated AC voltage.


So i turned on the machine anyway to check power supply functions, MPU and so on. Both monitors receive power, but no signal. The MPU doesnt boot, but one red LED does illuminate briefly. All of the power indicator lights on the backplane are on, but 2 blink in unison with the service light.


The fans on the MLD monitor run and the printer and BV both have power.


Could my problem lie with the Main Power Distribution Box? Anyone see one of these go bad? Or could the MPU be bad?


I'm just confused about the lights blinking on and off, which seems to me like a power problem.


I'll have to look again and see which lights were blinking on the backplane.


Thanks,
Curtis ash100

[rickhunter]

Does the MPU beep once a few seconds after power is applied?

[Ash100]

No Rick,


I never get the tone/beep upon start up. I do get one red light momentarily and if the Diag and EKey are inserted, the green light inside the Ekey illuminates briefly.


So it's quite possible I have a bad MPU. But I'm just confused as to why my A/C Line Voltage is cycling. And would that have anything to do with the MPU not booting?


Curtis ash100

[rickhunter]

AC line voltage cycling is probably bad power supply.  Pull out the main power supply and see if the ac still fluctuates when you power up. My G20 cabinet had a burned power connector that was giving me issues.  I changed the molex plug and cleaned the contacts to fix it.

[Ash100]

Got back on this today,


So, with the power supply pulled, the line voltage still cycles.
The service lamp just blinks on and off as do two of the power indicator LEDs on the backplane. The 12V COM and 5V COM. And they continue to blink even when the switch is not to the on position. Not sure what those indicate or if they're even important.


I'm going to swap in a different MPU to see if it boots. It's from an older S-AVP machine that I never could get to load the OS, but at least I was able to see messages on the screen.


I'll post more shortly.


Curtis ash100

[rickhunter]

If you pulled the power supply and you are still getting the blinks, you have some sort of short.

[Ash100]

It may take a while to go through everything to trace that short, but I've got the time. I just bought this machine to learn it and play around with it.


I put the other MPU in it and was able to load the OS, so now I've got something more to work with. I have an OEM Loader and License, and was able to load the game.


I'll go back into it later and do a wipe and set everything up from scratch. I have no idea what's on the hard drive that I installed.


I'll still need to figure out why the other MPU failed to boot.


Thanks for your help.


Curtis ash100

[rickhunter]

I would start by removing the MPU completely form the cabinet, then unplugging everything in the backplane (take photo or label harnesses to make sure you can put it back together).  Then with everything disconnected from the backplane, power up and see if you still get the blinks.  If you do, then you probably have the short in the power distribution module (where the power cord plugs in).  If you don't have blink with everything unplugged, then with power off.  Plug one connector, power on, look for blink.  Rinse and repeat until you find the harness that causes the blink and go from there.  Never plug anything when you have power, make sure you power down between each plug (in your case you probably have to unplug power cord during each harness test because it is happening even with power switch off).

[Eddiie]

I found that there is a circuit breaker on the PDU thing.    See if it is tripped by chance?  Probably not, it would cut all the AC power if it was blown but might be worth a try?

[Eddiie]

Replaced the power supply in the PDU and it resolved the blinking 5V, 12V COMM LEDs on the backplane.
I got it from this seller - https://www.ebay.com/itm/264996530070

Plug and play.

[Ash100]

Thanks Eddiie,


I'll give that a shot. That's the only component that I haven't tried in my troubleshooting.


I followed your post and am impressed by your tactics. Glad you were able to get things up and running.


I'm still down a top LCD, so I'm not sure when I'll get back to that machine.


I purched a new 20" Display, but it was 2" taller than my frame. Same width and diagonal measurements, but taller, so not compatible. Not sure now what I can do to find the correct monitor. I don't want to keep purchasing the wrong ones.


Maybe there's some differences between the original G20 and the G20V2?


Anyway, I'll order that power supply and at least have it on hand for when the time comes.


Thanks for the link.


Curtis ash100

[Ash100]

Solved the problem with the power supply mentioned above.


Lights no longer blink on the backplane.


I'd forgotten about how much of a pain it is to get the Power Distro Box out.


Thanks for the tips!


Curtis Ash100

[Slotman]

One of these guys in your tool bag saves a lot of head scratching.  And for $15.00 dollars its money well spent.
https://www.amazon.com/gp/product/B00Q8SUYHW/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1
The only thing that would be better would be if you could put it inline with the power supply so you can see voltage with a load on it.