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Author Topic: A2000 went from semi to no boot, black screen  (Read 775 times)

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Offline RetroNinjaTopic starter

A2000 went from semi to no boot, black screen
« on: October 26, 2022, 12:18:04 AM »
Hello!

I have an A2000 with an A2620 accelerator, WB1.3, rev 6 mobo, the battery was previously replaced with a coin cell (but not the kind with a diode, just a coin cell holder). The corrosion under the battery does not look too bad.

Previously it would boot if I held down both mouse buttons and selected A2620 as the boot option. If I chose the 68000 (onboard) it would also boot fine. Full WB and I could run programs. If I pulled the A2620 it would boot a couple times off the 68000 then it would stop and I would only get a black screen. If I left it off for any amount of time it would never boot to the 68000. Once I re-installed the A2620 it would start booting again under the above listed conditions.

I popped the 68000 out and noticed corrosion in the CPU socket. Having no DeOxIt I just replaced the CPU socket. It is always my preferred option anyway. While toiling away on the mobo I also straightened all of the capacitors, meaning I just bent them all in one direction.

Now the board does not boot at all. I can put the A2620 in and get the boot options but nothing boots to WB with either the 68020 or 68000.

My thinking is that the capacitors may have been causing the problem all along. Without the A2620 installed, whatever caps manage the CPU's voltage are bad. Once the A2620 is installed the 68020 takes over and runs everything. So maybe the 68000 CPU cap was charged to spec with the A2620 installed (power draw?), as it booted a couple times (w/no A2620) the bad cap does not re-charge causing the black screen.

What's your idea for a fix?

Also any ideas on placing a diode inline with the coin cell (where + value)?
 

Offline RetroNinjaTopic starter

Re: A2000 went from semi to no boot, black screen
« Reply #1 on: November 01, 2022, 03:37:25 AM »
I did try another 68000 CPU. No change to the booting scenario.
 

Offline RetroNinjaTopic starter

Re: A2000 went from semi to no boot, black screen
« Reply #2 on: November 01, 2022, 03:42:31 AM »
I did pull the ROM and noticed some corrosion on a few pin holes in the socket. It didn't look too bad though. Granted, I didn't dig all of the way down into the bottom of the pin hole. I'll put it on my list of 'things check/trace' :)

Also, since it was booting into WB1.3 fine (in the scenario listed) before the CPU socket swap it is lower on my list, but the hint did prove/find corrosion. Thanks!
 

Offline RetroNinjaTopic starter

Re: A2000 went from semi to no boot, black screen
« Reply #3 on: November 01, 2022, 03:45:52 AM »
I though I was ready to start a recap job but I've got no 4.7uF or 22uF at 35V :( Time for a Mouser order.

Huh, I just noticed my replies are not tying back to the posters. You know who you are, thanks.
« Last Edit: November 01, 2022, 03:48:10 AM by RetroNinja »