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Old 08 July 2012, 17:39   #1
Stedy
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Eek Dead A500, need some advice

Hi,

In order to test an A500 memory expansion, I dug out my A500. Powered it up, only got a black screen. Need some advice on what to try next.

I'm using a 90W picoPSU to power it, there is 4.90V at the MC68000 and some of the logic chips. Though I have a black screen, the composite video output has a video signal, with no content so the video timing works.

Removed, cleaned and reseated all socketed ships. Removed all RAM expansions, floppy drive does not seek (checked the cable is correctly inserted). Was looking to re-cap this but removed a tested the main power supply caps, all tested Ok for capacitance and ESR.

It's a Rev 6 A500 with 512K RAM, nice and clean too. There is no RTC on-board, that is on the RAM expansion, which has no leaking battery.

Suggestions please?

Ian
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Old 08 July 2012, 18:28   #2
roy bates
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hi stedy,did the machine work in the first place?

is there a signal through the rgb port?

is the rom ok?


have you got another machine for parts? if you have try swapping out the cpu,agnus and denis.
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Old 12 July 2012, 01:04   #3
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Hi, answering the questions

Quote:
Originally Posted by roy bates View Post
hi stedy,did the machine work in the first place?
Yes it did work when purchased, back in 2005.

is there a signal through the rgb port?

Will double check it this weekend but I think the scandoubler had no video.

is the rom ok?

I'll double check I put it back correctly. It's a Kickstart 1.3 ROM. Could borrow the Kickstart 2.05 from my A600.

have you got another machine for parts? if you have try swapping out the cpu,agnus and denis.
I don't have another A500 unfortunately.

Will play some more this weekend.

Ian
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Old 14 July 2012, 06:44   #4
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Sounds like a dead CPU, my friend. But Roy advice is the better.

I think you must grab another A500(+) to sort out your problem.
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Old 15 July 2012, 23:55   #5
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Bummer, looks like the machine is dead.

I probed the databus, D0-D7 are stuck at 1.8V, not good. AS toggles once and the address bus is static. Might just be the MC68000 but will look around for another machine.

Ian
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Old 16 July 2012, 00:07   #6
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if you want a cpu 68000 tested, send me a pm
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Old 16 July 2012, 00:26   #7
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Just had a thought!! I'm sure I seen a spare 68000 in a box somewhere (edit) couple of pounds postage?

Last edited by keitha1200; 24 July 2012 at 01:04. Reason: mistake in my post
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Old 24 July 2012, 00:39   #8
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@keitha1200

Have you got the MC680000?
If you have, send me a PM with the price, with delivery please.

Ian
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Old 24 July 2012, 00:52   #9
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Hi Ian,

did you try swapping the CIA chips (8520's) see if it boots after swapping
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Old 24 July 2012, 01:01   #10
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I think it's a MC68000P. Can do the cpu for postage cost but can't guarantee the cpu. PM sent

Last edited by keitha1200; 24 July 2012 at 02:20.
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