I think my CPU is fried (A600)

Redwood · 04 September 2012, 05:16

When I turn on my A600 all I get is a blank, black, screen and no disk or other activity.

When it was was working there would be a short series of screen color changes before disk activity started (or the kick start screen appeared). I gather from other posts that the first thing the machine does on boot is check the CPU, then change the screen color, so I guess my CPU is dead. Can anyone confirm?

Anything I can do about it, or should I start making funeral arrangements?

bdb · 04 September 2012, 05:52

Make sure the PSU is working; grab a multimeter and check voltages out of the PSU and into the A600; after a few minutes see which chips are warm or worse hot; smell for burnt stuff...

Better yet wait for someone who has been through "dead-ish" 600 before.

Rebel-CD32 · 04 September 2012, 07:21

Does the Caps Lock light come on? If you leave it for over ten minutes, does anything change? It seems like all the A600s in the world are getting this black screen problem lately, a few of mine did and several other forum posters. It's probably a capacitor problem, possibly PSU-related sometimes too, but it's most likely the caps. AmigaManiac can replace them, I see he's back and working again now and you'd be hard pressed to find someone closer who can replace the caps for you for what he charges.

ferix · 04 September 2012, 08:59

Quote:

Originally Posted by Rebel-CD32

Does the Caps Lock light come on? If you leave it for over ten minutes, does anything change? It seems like all the A600s in the world are getting this black screen problem lately, a few of mine did and several other forum posters. It's probably a capacitor problem, possibly PSU-related sometimes too, but it's most likely the caps. AmigaManiac can replace them, I see he's back and working again now and you'd be hard pressed to find someone closer who can replace the caps for you for what he charges.

I bet on that.
Mine had same symptoms, and It came back to life after replacing some caps.

XimeR · 04 September 2012, 09:47

My A600 does this too. If I leave it powered on for about 30mins or so, then reset it, it magically comes back to life.

I think it's a caps problem. I should really get it fixed someday.

majsta · 04 September 2012, 11:30

Ok first step to confirm that CPU is dead is related to DTACK. You must confirm that when you drive DTACK low nothing happens. So basically start your A600 and use wire connecting GND to DTACK. Use datasheet for MC68K and find where DTACK is. When you do that it could drive to changing colors on display, if not you need to check also RESET and CLK signal to see that they are OK and if all input signals are present here and no movement on output signals CPU is dead. Basically that is the principle but you must understand that there is no way to tell what's wrong without using Logic Analyzer, and only thing you can do is to test it like described using taking DTACK low.

jbenam · 06 September 2012, 01:12

Probably a caps problem. Check out for leaking. My A600 (I have since changed mobo as I didn't have a good soldering station back then... oh, the horror) had leaked caps all over the RESET TIMER and that made the black screen appear (I think, never had the chance to verify it

).

The best thing you can do is change all the caps, if it still doesn't work, then check out for leaks around the old caps and verify the nearby ICs (reading the A600 service manual can also give you a good idea of how the various ICs are interconnected, so that you can test for continuity).

04 September 2012, 05:16	#1
Redwood Registered User Join Date: Jun 2008 Location: Sydney / Australia Posts: 83	I think my CPU is fried (A600) When I turn on my A600 all I get is a blank, black, screen and no disk or other activity. When it was was working there would be a short series of screen color changes before disk activity started (or the kick start screen appeared). I gather from other posts that the first thing the machine does on boot is check the CPU, then change the screen color, so I guess my CPU is dead. Can anyone confirm? Anything I can do about it, or should I start making funeral arrangements?

04 September 2012, 05:52	#2
bdb Registered User Join Date: Jul 2012 Location: USA Posts: 239	Run down other causes than the CPU Make sure the PSU is working; grab a multimeter and check voltages out of the PSU and into the A600; after a few minutes see which chips are warm or worse hot; smell for burnt stuff... Better yet wait for someone who has been through "dead-ish" 600 before.

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04 September 2012, 07:21	#3
Rebel-CD32 Amiga will never die! Join Date: Nov 2004 Location: Tasmania, Australia Age: 43 Posts: 532	Does the Caps Lock light come on? If you leave it for over ten minutes, does anything change? It seems like all the A600s in the world are getting this black screen problem lately, a few of mine did and several other forum posters. It's probably a capacitor problem, possibly PSU-related sometimes too, but it's most likely the caps. AmigaManiac can replace them, I see he's back and working again now and you'd be hard pressed to find someone closer who can replace the caps for you for what he charges.

04 September 2012, 09:47	#5
XimeR Registered User Join Date: Mar 2009 Location: Warrington, UK Age: 47 Posts: 116	My A600 does this too. If I leave it powered on for about 30mins or so, then reset it, it magically comes back to life. I think it's a caps problem. I should really get it fixed someday.

04 September 2012, 11:30	#6
majsta www.majsta.com Join Date: Jun 2010 Location: Banjaluka/Republic of Srpska Age: 43 Posts: 448	Ok first step to confirm that CPU is dead is related to DTACK. You must confirm that when you drive DTACK low nothing happens. So basically start your A600 and use wire connecting GND to DTACK. Use datasheet for MC68K and find where DTACK is. When you do that it could drive to changing colors on display, if not you need to check also RESET and CLK signal to see that they are OK and if all input signals are present here and no movement on output signals CPU is dead. Basically that is the principle but you must understand that there is no way to tell what's wrong without using Logic Analyzer, and only thing you can do is to test it like described using taking DTACK low.

06 September 2012, 01:12	#7
jbenam Italian Amiga Zealot Join Date: Jan 2009 Location: Italy Age: 36 Posts: 1,912	Probably a caps problem. Check out for leaking. My A600 (I have since changed mobo as I didn't have a good soldering station back then... oh, the horror) had leaked caps all over the RESET TIMER and that made the black screen appear (I think, never had the chance to verify it ). The best thing you can do is change all the caps, if it still doesn't work, then check out for leaks around the old caps and verify the nearby ICs (reading the A600 service manual can also give you a good idea of how the various ICs are interconnected, so that you can test for continuity).

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