17 February 2024, 04:09 | #1 |
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A500 and GVP A530
I was gifted a A500 rev 6a / GVP a530 combo
was sitting in a closet for 30 years, my friend pulled it all out and plugged it in to show me it works. bundle it up took it home Everything seems to work, but by itself the A500 powers on but never shows the insert disk screen and the screen remains dark. Plugging the A530 back in the sideport it powers up fine. I'm thinking weak Power supply (everything is original)? I updated the rom from 2.04 to 3.1 and updated the rom on the gvp a530 from 4.5 to 4.15, Laine |
17 February 2024, 09:27 | #2 |
Also known as GarethQ
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Very first thing is to open up both machines and look for leaking capacitors and if your a500 is a plus model, cut the variable battery out. Also look for these same issues in the slot underneath the machine if it has a memory expansion populated.
Was it working before you updated the roms? |
18 February 2024, 02:52 | #3 | |
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Quote:
I opened both and cleaned the dirt and grim with alcohol and used some deoxit on it. The monther board is a rev6 not a plus so has ECS chipset Battery on the Supra expansion card (512K) has a 2032 on it removed it but no leaks on it. the jp7 trace was cut to add it to the chipram (1meg) has a switch attached to the jp4 beside the agnus looks like a PAL/NTSC switch besides not powering on without the GVP plugged it it all seems to work, if I hit the switch on the a530 it boots to the insert disk screen , flip it back it books to the OS fine. remove the GVP and black screen will check for blinking power lights etc was hoping for a quick fix |
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19 February 2024, 04:05 | #4 |
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Have you tried re-seating the MC68000? Thinking out loud...if it works with the A530 and fails without...this may point to a CPU issue on the A500 or something leading to a CPU issue.
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19 February 2024, 23:46 | #5 |
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Good question , I have not tried reseating the 68000, I do have I believe a known good one
I will try both, I did download the diagrom from Chucky's website working on programming a chip ones it's erased |
20 February 2024, 00:12 | #6 |
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I put in the known good 68000 CPU in, boots to insert disk screen in 3.1 (yah!), will test back and forth.
I guess the a530 would bypass the 68000 for the 030 more, more testing is needed |
20 February 2024, 00:24 | #7 |
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pulled the known good out, ran an eraser over the pins of the old CPU, put it back in no boot screen stays black.
put the spare in and boots to 3.1 insert disk screen fine going to say problem solved still going to put in the diagrom and do a full test |
20 February 2024, 07:18 | #8 |
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I'd say problem solved too. As you said, the A530 will take over the bus and the motherboard 68000 is not used for anything.
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20 February 2024, 09:03 | #9 |
Also known as GarethQ
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Well, that was a good result even if you have a dead part. Let the fun begin.
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04 May 2024, 03:45 | #10 |
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The reason the A530 allowed the system to work is it holds the system _reset down (with the relay in the back), which allows the A530 power to stabilize, then HW requests/steals the bus before the 68000 can even get started. After that, the driver is looking for a SCSI device to boot from, or times out.
I'd bet the GVPCPUCtrl command's fallback to 68000 option would have also revealed the faulty 68000. It gives the bus back to the A500 motherboard's CPU (and the A530 is fully disabled until a Ctrl-A-A is done). |
04 May 2024, 20:47 | #11 |
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That's very good information, thank-you. it's been pretty solid as I've played around with it, I still need to do caps on it, not sure if the A530 needs caps too?
trying to do PFS filesystem in/on a zuluscsi image in the A530, not having much luck, also I have the 'old' drive I'd like to image it's from the early 90s sounds levels when it's spinning is crazy Laine |
04 May 2024, 20:50 | #12 |
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No need to change the caps on A500 ...
Don´t try to fix something that isn´t broken |
05 May 2024, 01:26 | #13 |
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The caps on the A530 are ceramic SMDs (near the chips) and possibly a few some tantalum around the corners. All are for digital switching ring cleanup and FCC. The bigger values (FC#) could be replaced with high-quality Panasonic hybrids with no issue.
Put a multi-connector cable on the unit (termed), the native drive, and your Zulu. (Terminate), and do a copy-off. Use HDToolBox for the prep of the new unit. Hint: you need the correct FS image saved in the boot block (not FFS) and the proper DosType value on the partition in the RDB. |
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