Dead A500, need some advice

Stedy · 08 July 2012, 16:39

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

roy bates · 08 July 2012, 17:28

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.

Stedy · 12 July 2012, 00:04

Hi, answering the questions

Quote:

Originally Posted by roy bates

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

rkauer · 14 July 2012, 05:44

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.

Stedy · 15 July 2012, 22:55

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

cpiac64 · 15 July 2012, 23:07

if you want a cpu 68000 tested, send me a pm

keitha1200 · 15 July 2012, 23:26

Just had a thought!! I'm sure I seen a spare 68000 in a box somewhere (edit) couple of pounds postage?

Stedy · 23 July 2012, 23:39

@keitha1200

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

Ian

kipper2k · 23 July 2012, 23:52

Hi Ian,

did you try swapping the CIA chips (8520's) see if it boots after swapping

keitha1200 · 24 July 2012, 00:01

I think it's a MC68000P. Can do the cpu for postage cost but can't guarantee the cpu. PM sent

08 July 2012, 16:39	#1
Stedy Registered User Join Date: Jan 2008 Location: United Kingdom Age: 46 Posts: 733	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

15 July 2012, 23:26	#7
keitha1200 Registered User Join Date: Feb 2012 Location: Tayside Posts: 181	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 00:04. Reason: mistake in my post

24 July 2012, 00:01	#10
keitha1200 Registered User Join Date: Feb 2012 Location: Tayside Posts: 181	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 01:20.

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08 July 2012, 17:28	#2
roy bates Registered User Join Date: Apr 2011 Location: birmingham Age: 55 Posts: 2,827	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.

14 July 2012, 05:44	#4
rkauer I hate potatos and shirts Join Date: Oct 2007 Location: Sao Leopoldo / Brazil Age: 58 Posts: 3,482	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.

15 July 2012, 22:55	#5
Stedy Registered User Join Date: Jan 2008 Location: United Kingdom Age: 46 Posts: 733	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

15 July 2012, 23:07	#6
cpiac64 Registered User Join Date: Apr 2010 Location: Italy Posts: 1,136	if you want a cpu 68000 tested, send me a pm

23 July 2012, 23:39	#8
Stedy Registered User Join Date: Jan 2008 Location: United Kingdom Age: 46 Posts: 733	@keitha1200 Have you got the MC680000? If you have, send me a PM with the price, with delivery please. Ian

23 July 2012, 23:52	#9
kipper2k Registered User Join Date: Sep 2006 Location: Thunder Bay, Canada Posts: 4,323	Hi Ian, did you try swapping the CIA chips (8520's) see if it boots after swapping

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