A1000 rebuild / fault finding

[mjnurney]

My original A1000 , my first one died one day about four years ago ...i don't know why but one day it never booted again. black screen.

i did the usual thing , changed all the socketed chips but no nothing..so it was packed away in the dead section for a year or three.

Well yesterday i got the lets fix it bug...

but no A1000 PSU , ill hot wire a pico PSU ...dont like that , ill hot wire an A2000 PSU as it has the tick signal...ok.

i changed all the socketed chips again from a working 500 , except Agnus. No joy here.

i then fitted a kickstart adaptor that i borrowed about 4 years ago ....must return it, that didn't work either but i did get a faint beep at power up.

now i had no boot up sequence of lights, no kickstart , zip...just a black screen but a quiet beep.

i tried other kickstart in the adaptor but either nothing or quiet beep.

So maybe its ROM related , the power light flickers too?

i removed the kickstart adapter and put it back as normal ...and nothing,its dead. So what if i try the ACA500 either though Jens says do not fit it. the pinouts are the same on a500/a1000 just incorrect orientation.

and bingo it lives! , I've hot wired an A500 keyboard on to the 1000 for the moment. Data, clock,gnd,+5v

video & audio all good.

So whats actually wrong? well the kickstart ROMs (79,80) are dead i think , I've ordered two more from Germany but its alive...first time in 4 years

MOS
252179-01
©1985 CBM
5185 TAIWAN
28005A-0054

MOS
252180-01
©1985 CBM
5085 TAIWAN
28005A-0055
now i can get back to sleeping properly , 2am bedtimes are no good!

2am video below


https://www.youtube.com/watch?v=au9TKd-zGpM


ultimately I'm going to rehouse this in a good A1000 case , clean up the keyboard and make a pretty A1000 and plonk an big heavy commodore CRT screen on it


A1000 pinout data.

Keyboard +5v, data,clock,ground (my 5v line is about 5.18v)

motherboard---| GND
PCB ............---| CLK
here............---| DATA
..................---| 5V

A1000 PSU connector (motherboard end)

1 * -5v
2 * +12v
3 * GND
4 * GND
5 * +5v
6 * +5v
7 * tick sync

A500 keyboard connector (wire end)

1 DATA
2 CLOCK
3 (not needed)
4 +5V
5 (no pin here)
6 GND
7 (not needed)
8 (not needed)

A2000 PSU pinout

YYYYBBBBO RGWU

U=Brown wire
gap = missing wire in connector

or
1 +5
2 +5
3 +5
4 +5
5 GND
6 GND
7 GND
8 GND
9 +12
10 no wire (keyway)
11 -12
12 +5 USR
13 -5
14 TICK

 

[BloodyCactus]

nice work! I dont think I've seen an pal A1k mobo, only ntsc with daughterboard. nice! kinda surprised that your masked boot roms are dead. if you have the right type, you can replace them. they are 256kbit eeproms. I cant think of the type offhand

 

[mjnurney]

Yes it's a strange one

not sure I have the EPROMs or the odd & even bin files anyway

 

[BloodyCactus]

I have the odd/even files if you need them, I read them from my NTSC miggy 1k, now I dont know if there were differences in the boot of pal vs ntsc or not, but I have them somewhere if you need them

 

[cpiace64]

i need verify if i have original working proms for your mainboard and a psu, tomorrow update with more info

 

[mjnurney]

great stuff

 

[cpiace64]

rom ok, psu in test

 

[mjnurney]

Brilliant , great stuff

do you have a 1000 floppy?

 

[cpiace64]

the floppy at the moment is on gba1000 in the house of my friend in Venice but i can send a pm for shipment to me for verify if work

the my psu need a new fan or you can use your and other test

 

[mjnurney]

i'll send you a Pm bud.

 

[mjnurney]

So a little more on the 1000.

I have been sent a set of used ROMS 79,80 but i still get no boot screen for some reason? just a black screen. Oh well.

but i do have a new PSU , yay posted very quickly and plugged in and fitted so I'm only short of a floppy drive at the moment then i can build it up finally.

So the black screen....

no boot sound and no white kickstart just a black screen and an occasional low pitched bleep but no jingle.

The only chipset chip i haven't changed is the Agnus 8367 as its DIP in the 1000.

mike.

 

[cpiace64]

sorry for delay but my psu is dead

 

[mjnurney]

no worries , as you see i got a new / old one in the end