ST536 -- how to check if working/what's broken?

[szeremiocki]

Hi,

I am one lucky owner of ST536 in Mega ST. And, I apparently commited some kind of stupidity, resulting in booster not working _at all_.

Background: some weeks ago I acquired old pak68 card, sold as untested. Just base board, without RAM, only 68020, FPU and oscillator for 16MHz clock (http://amiga.resource.cx/exp/pak). After some small fixes (replacing damaged connector pins), I decided to test it in my Mega ST -- replaced ST536 with this card, and actually booted my Mega ST, from emutos/128KB on cartridge -- needed because of long stack frame on 68020.
All great, I was very excited with my first 'repair', but after I tried to switch pak68 to higher frequency (two jumpers on board, selecting onboard oscillator), card no longer booted in _any_ configuration. Screen is yellowish with slight thrash (or white in other MegaST), nothing happens.

But real tragedy was when I temporarily gave up PAK and returned to ST536: apparently I wasn't carefull enough, and switching cards I managed to bend and eventualy break couple of ST536 DIP64 connector pins :(. I replaced both DIP connector strips with new ones, checked board for any additional physcal damage, even tested conductivity for most of connector signals (especially broken ones) -- I dont see any additional damage. BUT ST536 also doesn't boot -- yellowish slightly thrashed screen, nothing happens. Checked ST536 in my other Mega ST -- same. I have to assume that I somehow broke this card. Single day, two cards trashed :(
Said MegaST works fine with 68000 of course...

I still hope that I didn't actually terminally damage this ST536 treasure. So, how do I proceed? How can I check what is wrong with card? Is there a possibility that reflashing can help? How do I do it? Or, how do I check for other possibilities of repair? Do you have any suggestions?

Regards and thanks in advance,
Przemek Szeremiota

[Darklord]

Did you try the Pak board in the 2nd machine?

[szeremiocki]

Did you try the Pak board in the 2nd machine?

Yes… same effect as st536: bith cards give just the white screen (yellow rubbish is in first megast with both cards) :(

[Badwolf]

Is there any difference to the "yellowish thrash" if you power up the machine with *no* CPU?

This will basically confirm the "yellowish thrash" is the underlying motherboard rather than the processor board and give you a starting point.

Next: diagnositic cartridge.

BW

[szeremiocki]

Well there is no difference between pak68/st536 or no CPU at all: yellow gibberish on first megaST, white screen on second MegaST, no further activity; diagnostic cartridge doesn't start, nothing on screen.

Everything dandy with mc68000.

Seems like the boards are really dead? Pak68 I can try to recover (bunch of discrete logic components in place of GAL, each of them can be tested (in tl866?)/replaced; cpu/fpu/oscillator -- also.

But with the ST536 I don't even know where to start with a repair/diagnostic.
I have one more bird-seeded ST536 board and even a full set of needed components -- but am still afraid of wasting it with my skill/luck. Is there some kind of standalone ST536 debug/bringup/test mode? How one does st536 xilinx-chip programming? Could I try to connect through jtag pins? should I provide power through PWR2 pins?

[exxos]

I'm confused as you have to build the ST536 up yourself unless you purchased it already built from someone else ?

You mentioned repairing some pins come out are you totally sure you did not damage any of the vias ?

Does the PLD get extremely hot ?

I cannot say how to verify the pld you will have to look on the guides on the forum or the internet on how to verify the pld to see if it is dead or not.

[szeremiocki]

I'm confused as you have to build the ST536 up yourself unless you purchased it already built from someone else ?

You mentioned repairing some pins come out are you totally sure you did not damage any of the vias ?

Does the PLD get extremely hot ?

This one was built for me, the second one I wanted to build for myself so I collected board/parts. But I have to get better at soldering and need some more tools.

Anyway, I will try to check all vias, thanks for advise.
PLD stays warm after couple of minutes (temp similar to 68030)