RE: Stuck output(s) on G80 X/Y Cards / CPU no LED.

Yep, those extra ground planes reduce crosstalk between pins, and probably help control impedance - imagine adding a 12" antenna to 4/8 Mhz clock signals; they'd get sloppy pretty fast.

Thanks,

Chris Brooks
713-341-9850
-----Original Message-----
From: owner-vectorlist@vectorlist.org [mailto:owner-vectorlist@vectorlist.org] On Behalf Of Andrew Welburn
Sent: Wednesday, January 18, 2012 3:56 AM
To: vectorlist@vectorlist.org
Subject: Re: VECTOR: Stuck output(s) on G80 X/Y Cards / CPU no LED.

On 18/01/2012 03:13, Mark Jenison wrote:
> When I was over at Rick Schieve's one day, I found a few of these in
> his barn that he had been cutting up to make Jamma harness finger boards:
>
> https://plus.google.com/photos/113324346917953965256/albums/5698800677
> 317070049
>
>
> 86 pin extender cards that fit in G80 cages. They are labeled "OCTO
> CARD EXTENDER". I hope to get some use out of them as I've got a stack
> of about 40 CPU boards to repair.

The octo card extenders you mention are actually from Atari 'Indy' pcbs, sets like indy 800, indy 4 etc... shame to cut them up! but remember there are some joined pads on the finger edge that aren't on the g80 set. they are one card from a set of three needed to service Indy pcbs :
http://www.andysarcade.net/pix/AA01709.JPG (2 sets shown)

I actually found a real g80 extender card in Tulsa, OK (with the indy extenders above) at an operators place a few years back...
http://www.andysarcade.net/pix/AA01707.JPG

Notice the switch mounted in the upper right. The pcb has a ground plane running through the pcb, and you see they've etched ground traces alongside each of the pad->pad traces, presumably to counter noise?

--
Andrew Welburn
http://www.andys-arcade.com
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