Re: IIgs won't start up -- ZipGS dead?

["Bryan Parkoff" <nospam@nospam.com>]

"Mitchell Spector" <mitch2gs@hotmail.com> wrote in message 
8i7vc2dg3njccdso7f1u83nfpvd9hl0ff2@4ax.com">news:8i7vc2dg3njccdso7f1u83nfpvd9hl0ff2@4ax.com...
> "PZ" <skierpaul@yahoo.com> wrote:
>
>>> This is a 15/64 configuration ZipGS, which I've been running lately
>>> at 12.5 MHz. I hope I can get it going again, I find the machine
>>> unbareable any slower.
>>
>>My first question is, was this ZipGS a custom high speed zip directly
>>from Zip Technologies? They supposedly sold some 14mhz units with a few
>>with additional IC's soldered upside down onto the card, I have never
>>seend one in person.  These are extremely rare due to the price that
>>they were selling them for.
>
>    It is a user moded board (not by me, another Apple II user did it).
> From what I recall he cut the bridges between the SRAM sockets,
> and in-between, soldered in single socket row strips so it can make
> use of either wide or narrow cache chips. He installed narrow chips
> (rated 15 ns) for TAG, and wide chips (rated 45 ns) for DATA.
>
>    A full-sized oscillator socket was soldered in, as well as a socket
> for the chip at U8 (which had a 74HCT00E plugged in) with the
> other chip next to it left as is. A standard WDC 14 MHz CPU was
> installed, with a tin oscillator which was tightly zip-tied down.
>
>>The first thing to check is the XTAL, I've had a few go bad from
>>mishandling.  The 'can' type can get inserted backwards easily, once
>>thats done, they're done.  Find a 40mhz one just for stability testing,
>>then go up from there.
>
>    Since it was locked in with a plastic zip tie, there is no chance of
> that. I cut it off the tie last night and tried a 40 and 60 MHz oscillator
> with no change--though, I did notice something odd (more below).
>
>    When I powered up with the oscillator removed, I noticed this:
> If I just barely touch the bottom half of the empty socket, the yellow
> LED on the ZipGS lights up. Pressing Control-Reset turns it off.
> If I hold my finger down on the socket when powering up, the
> yellow LED comes on. With different oscillators (maybe because
> of longer pins?) sometimes it'll light up on its own and stays on;
> momentarily blinking off during a Control-Reset.
>
>    Is it possible there's a micro fracture crack in the pin solder joints
> for the oscillator socket? I mean, is it normal for the yellow LED to
> light on from just lightly touching the socket or oscillator?
>
>    I'm now leaning towards the oscillator socket being at fault,
> especially since I pressed on it _just_ before the ZipGS went
> dead (I also pressed on the socketed chips and CPU cable).
> I'm pretty sure, even when a GS refuses to start up and in a
> "dead" state, both the yellow and red LED should light up, no?
>
>>You'll probably end swapping out everything.  RAM, Xtal, cable, even
>>the CPU and 74xx IC's on the board.  Whats on the board now 74HCT's?
>>
>>If the board still doesn't work, you'll know its either the ASIC or a
>>capacitor derived issue.
>>
>>I'm assuming that you're using skinny cache ram, if you don't have
>>spares, you'll want to find an old Socket 4,5,7 motherboard with some
>>15 ns rams on them.
>>
>>The ribbon cable/connector is a standard straight through type, not the
>>wierd crossover type the TWGS uses, so they're easy to make.
>
>    If it is the oscillator socket, then a simple resoldering is all that
> would be needed. Unfortunately since I don't own a solder pen
> and have _zero_ experience with one (I'm not about to practice
> on my ZipGS heh) I'm no better off. :(
>
> Mitchell Spector

Mitchell,

    Well, I remembered when I bought ZipGS from you.  It had been working 
for about two years and then it went dead.  I had verified with //SHHH 
Systeme to claim that it could be the fault of ASIC chip.  It was impossible 
to repair.  Transwarp GS is working fine until today.  I am sorry to hear 
what you had experienced.

Bryan Parkoff