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Author Topic: A2000 went from semi to no boot, black screen  (Read 271 times)

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Offline RetroNinjaTopic starter

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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 scuzzb494

Re: A2000 went from semi to no boot, black screen
« Reply #1 on: October 29, 2022, 08:44:20 PM »
I had the same problem with a little corrosion on the CPU and getting the black screen. Then I had the bright idea of spreading the CPU legs out a little so thay fit may more snug into the socket. I aso cleaned the legs a lot. Since then I have had success with a GARY and DENISE doing the exact same thing. I'm not saying its going to solve anything but its worth a try if you haven't already.

Good luck.

PS The A2620 is probably a red herring. Just leave it out till you get the computer working with the 68000. I assume you checked all the traces around the battery area.

Offline utri007

Re: A2000 went from semi to no boot, black screen
« Reply #2 on: October 30, 2022, 01:00:41 AM »
A2620 has some capasitors wich gave more power to cpu bus. So capasitors are my suggest.
ACube Sam 440ep Flex 800mhz, 1gb ram and 240gb hd and OS4.1FE
A1200 Micronic tower, OS3.9, Apollo 060 66mhz, xPert Merlin, Delfina Lite and Micronic Scandy, 500Gb hd, 66mb ram, DVD-burner and WLAN.
A1200 desktop, OS3.9, Blizzard 060 66mhz, 66mb ram, Ide Fix Express with 160Gb HD and WLAN
A500 OS2.1, GVP+HD8 with 4mb ram, 1mb chip ram and 4gb HD
Commodore CDTV KS3.1, 1mb chip, 4mb fast ram and IDE HD
 

Offline mechy

Re: A2000 went from semi to no boot, black screen
« Reply #3 on: October 30, 2022, 05:09:07 AM »
I would start by checking the PSU voltages first at the motherboard connector.
Since you changed the 68000 socket i wonder if a broken or marginal trace is the problem,i would suggesting doing a continuity test on all the traces to make sure none are broken.
Check the kickstart socket too,not uncommon for them to suffer from battery corrosion.
Since the machine was working then got worse,i would pull the coin cell holder and investigate the damage under it. you can stop the corrosion with a cleaning of vinegar followed by iso alcohol.
Last but not least the capacitors are cheap to change and could very well play a part.
any common diode should work for the coin cell such as 1n914, but a Schottky diode has less drop and might be better(1n4148)for max coin life.
 

Offline Tumbleweed

Re: A2000 went from semi to no boot, black screen
« Reply #4 on: October 30, 2022, 04:29:11 PM »
I had a black screen with my A2000 last year. I replaced the 68000 CPU and popped out Agnus. Cleaned all the contacts and was back in business.

Check the CPU socket and the maybe try a different 68000 CPU (I got my replacement from Analogic); check all seated chips - pop them out clean the contacts and reseat them. 

Weed
A3000T, Cybervision64, CSMKII 060; A3000D, PicassoII, Z3 Fastlane; A2000D, 040, PicassoII; A4000D, A1200, Blizzard 030 MKIV - both not working :(
 

Offline RetroNinjaTopic starter

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Re: A2000 went from semi to no boot, black screen
« Reply #5 on: November 01, 2022, 03:37:25 AM »
I did try another 68000 CPU. No change to the booting scenario.
 

Offline RetroNinjaTopic starter

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Re: A2000 went from semi to no boot, black screen
« Reply #6 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

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Re: A2000 went from semi to no boot, black screen
« Reply #7 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 »