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Main => Main Forum => Topic started by: kenzo42 on April 24, 2005, 01:27:17 am

Title: 1, 2, A, B Grounds for J-Pac
Post by: kenzo42 on April 24, 2005, 01:27:17 am

why does the j-pac use these 4 grounds if there is no power 5v, 12v, -5v going to it?

on the ultimarc website, it says that these connections are used by the j-pac??? will the j-pac still work w/ out these 4 grounds?

Title: Re: 1, 2, A, B Grounds for J-Pac
Post by: SirPeale on April 24, 2005, 08:01:05 am

It's just ground; there's really no reason you'd want to cut it off.  It's getting ground from the PC.

Title: Re: 1, 2, A, B Grounds for J-Pac
Post by: kenzo42 on April 24, 2005, 02:36:28 pm

Hey Peale,

I understand that the pc has it's own ground. However, I notice that the 8 grounds traces (from pictures I've seen) are still intact, thus being used. The locations for these 8 grounds are 1, 2, A, B, 27, 28, e, f. Can you tell me what these traces lead to?

I need to split one of those grounds or find one that's not used (for a needed total of 9 grounds, jpac uses 8) to ground a 5v line. I will be powering something from this 5v line.

Thanks.

Title: Re: 1, 2, A, B Grounds for J-Pac
Post by: SirPeale on April 24, 2005, 02:41:25 pm

The grounds are all connected.  Get +5v from the power supply.

Title: Re: 1, 2, A, B Grounds for J-Pac
Post by: kenzo42 on April 24, 2005, 02:47:46 pm

I would, but I need to load +5v from my cabinet's psu, not from the PC psu. My cab's PSU goes into overload mode w/ out a board (ALL my wiring is jacked through the PSU, so I can't remove it). So I'm going to just load my PSU w/ a dummy jamma board, thus the 5v.

I just read this on Bob Robert's site, which is essentially the same thing you said:

<<The PCBs ground traces are all linked together on both sides of the board, so any place that is designated as ground on the PCB, is just that, logic ground, and unites all logic ground into one common termination back to the supply grounding point at your source of DC power.>>

So I'm assuming by splitting a ground, there won't be any problems since they are all linked together.

Title: Re: 1, 2, A, B Grounds for J-Pac
Post by: krick on April 24, 2005, 04:40:59 pm

Would this help at all?...

http://mame.3feetunder.com/jpacmod/

Title: Re: 1, 2, A, B Grounds for J-Pac
Post by: SirPeale on April 24, 2005, 04:43:09 pm

I'm going to suggest you rewire.  Having all the cabinet's AC wiring isn't the greatest idea.  And having to wire a PCB just so it doesn't blow?  Even less good.

Title: Re: 1, 2, A, B Grounds for J-Pac
Post by: dabone on April 24, 2005, 04:48:57 pm

Most cab power supplies have lug terminals.

If you must keep the cab wiring intact just remove the ac inputs from the power supply. (You can either clip the spade ends off and wire nut them or just wrap them with electrical tape.)

Then just add the voltages you need back to the wiring harness (i.e. +5 or +12).


Later,
dabone