What happened to my A500?

[Munchkin]

So. I made a huge mistake. I didn't read PROPERLY.

Decided to upgrade the 2.04 kickstart on my Rev 5 A500 to 3.1

I read that pin 1 and 31 should be connected as well as 31 and 21. Here's what my huge mistake comes in since I didn't read properly. You can probably guess it.

Well, anyways. Put the 2.04 back in and it's still dead so, my mistake caused some kind of damage somewhere, question is what? Only got a quick click on the floppy, a blink on the caps lock led and a snap in the monitor speaker when I turn it on. Nothing else. Black screen and no power led.

I guess I blew some chip but which one?

[TribbleSmasher]

I guess you did something else. Afaik you 'just' shortened one address line and one data line to ground, which should not do much harm?

[Munchkin]

I don't really know why I did what I did. I was rushing things and didn't think, at all. So I basically connected pin 1, 21 and 31 together.

But something did happen since it's now not doing anything when I power it on.

Had nothing happened it would have worked when I put the 2.04 kickstart and the 68000 back in but it's still dead.

[darksun9210]

So my rev 5 A500 with 3.1 rom, only has one jumper lead:-
from pin 21, to pin 31 on the legs on rom chip itself, with the leg of pin 31 of the chip bent out so it does NOT go in the socket.

now, as far as i can figure, on the rev5 socket:-

pin 01 - Address 17
pin 21 - 5Volts VCC
pin 31 - BYTE-WORD select?

on the chip:-

pin 01 - Address 17/18
pin 21 and 31 are VCC 5Volts.

this may help tracing :- https://www.amigapcb.org/ i know they only have the rev8 A500 board, but it's been enough for me to trace lines and figure things out previously.

so it sounds like something got a dose of 5 volts where it doesn't want it... i hope you can find it, and its an easy fix!
it would just double check my working - i'm about 3 whiskeys in so far this evening.  but it sounds like Address17/18 got a jolt.  i hope you've got a spare 68k chip , agnus and gary chip to swap out to test? give each of them the sniff test see if the magic smoke has come out...

[Munchkin]

I just feel so stupid. Had I just been patient and read properly this wouldn't have happened. Also, the old 2.04 kickstart with a cable connecting pin 1 and 31 across it probably contributed to fool me.

Oh well, I'm sure it's fixable, just need to figure out what's fried.

Tried to swap the CIA's but that didn't change anything. Maybe buy and old 500 to use for spare parts.

Looking at that layout it's quite different to my rev. 5 but one trace goes to Agnus pin 59 so I might just have fried Agnus.

[darksun9210]

no worries. i feel more trepidation than elation opening the lids on these beasties these days too!

a quick note on what i understand about that rev8 board that's on PCB explorer.
its a 42pin rom socket, and the chip is a 40 pin. so you shuffle the chip back in the socket, one away from the notch end. So pin 2 of the socket goes to pin1 of the chip, then pin3->pin2 and etc. etc. and the pin count goes like that all the way round.
so on PCB explorer, ignore the top two pins, 01 and 42, and reduce the pin number of the number your looking at, by one. hope that made sense.

i'd start with buzzing out traces first off. make sure no lines have been toasted

from what i can see, pin01 on the rom socket goes to pin42 on the CPU and edge connector one way across the board, and then pin77 of Agnus and pin 34 on Gary going the other way - terminating at resistor pack RP105. So not too far.

[Munchkin]

Problem is I don't have that RP105 on my rev 5 board so there are some significant differences.

But it probably leads to both Agnus and Gary on both so either, or both, might be fried.

Have to be honest and say this goes over my head. I've just had my A4000 away for renovation so I'm gonna ask if he can fix this as well. I just don't have the equipment and knowledge to do this right.

[darksun9210]

Fair enough. i'd do the same.
that'll teach me to not pay attention to my own rev5 board though re- RP105! lesson learnt there for me. woopsy!

[TribbleSmasher]

Is the rev8 board so different? In Amigapcb.org pin 21 is d11, pin 1 is a19, pin 31 is gnd.

So my rev 5 A500 with 3.1 rom, only has one jumper lead:-
from pin 21, to pin 31 on the legs on rom chip itself, with the leg of pin 31 of the chip bent out so it does NOT go in the socket.

now, as far as i can figure, on the rev5 socket:-

pin 01 - Address 17
pin 21 - 5Volts VCC
pin 31 - BYTE-WORD select?

on the chip:-

pin 01 - Address 17/18
pin 21 and 31 are VCC 5Volts.

this may help tracing :- https://www.amigapcb.org/ i know they only have the rev8 A500 board, but it's been enough for me to trace lines and figure things out previously.

so it sounds like something got a dose of 5 volts where it doesn't want it... i hope you can find it, and its an easy fix!
it would just double check my working - i'm about 3 whiskeys in so far this evening.  but it sounds like Address17/18 got a jolt.  i hope you've got a spare 68k chip , agnus and gary chip to swap out to test? give each of them the sniff test see if the magic smoke has come out...

[darksun9210]

yeah unfortunatly in this case. if you ignore the top two pins on the socket and move everything down one, as the rev8 has a 42 pin socket, and the rev5 has a 40pin socket/rom...