Help for saving this A4000

Cosmos · 11 October 2010, 11:07

zz

Loedown · 11 October 2010, 13:59

Bust out your oscilloscope, check clock signal to all GFX chips.

It looks like a timing fault, check the logic hardware around Lisa and also possible leaky diodes D504 etc. Video out connector, look for breaks where the connector pins right angle.

Zack · 11 October 2010, 18:32

It's my A4000 that Cosmos is trying to save

The AGA output went from working fine to totally dead in about 2 days. In between it became gradually worse. Right before the output went dead, I remember being able to boot with no Startup-Sequence to a WB screen that was relatively fine. But when dragging the screen 1/5 or more down, the output became something like in the video. Dragging it back up did not make it go away again. After a reset -> boot with no Start-Sequence I could do the same again.
Later that day the output completely disappeared totally.

Had the same graphics corruption on both the 23 pin connector, and on the output from my Indivision AGA. So I think that the video connector might be ok?

Cosmos · 11 October 2010, 20:34

I put some new soldering on all diodes and on all Alice's connectors !

Seems to work all the time now

Thanks a lot Loedown !

Maybe some micro-cracks like the 68000 on the A600 (http://eab.abime.net/showthread.php?t=55059&page=5)

I'll keep this Miga 2 or 3 days for more tests...

Loedown · 12 October 2010, 06:20

What do I win and where can I collect Cosmos?

Odd graphic faults like that are going to be because of fluctuations in the video path that can be caused by timing faults and leaky trx / diodes if all caps are done.

Zack · 04 August 2016, 14:05

Better a late reply than never!

Started to do some systematic diagnose on my A4000 today, and have concluded that as long as the A4000 daughter board is attached to the computer, use of native graphics output is very unstable, and will either lead to a black screen, or graphics corruption followed by the computer hanging.

Removing the daughter board, and the machine is stable when using native graphics.

However using CGX graphics modes with my CV64 card, attached to the same daughter board has also been very stable for hours at a time, until I started using a native graphics mode (by starting a game or demo with WHDload).

I assume that the daughter board might need to be recapped, but have asked a local Amiga group, if anyone have a working daughter board for me to test, to confirm my findings.

Just wanted to share an update on the trouble, and a possible solution

buggs · 07 August 2016, 20:29

Well, I doubt that standard issue recapping is the way to go for that Daughterboard of yours, although replacing old caps is never a bad idea.

The Daugtherboard features some Pullups and some Power stabilizing for attached cards but if there is nothing shorted on your board, the issue is quite likely somewhere else. I just recapped my A4k, where nearly every electrolytic capacitor had spilled its guts out. The Daughterboard was unaffected, btw. (due to standard issue axial caps instead of the dreaded SMD ones)

Interestingly, the Amiga seemed to work fine for quite some time (despite the condition of the caps). Only after it started to develop sound issues, I recently did the rescue (originally planned for the winter). Bottom line in my case: Most of the caps were gone and still, the tantalums on the Cyberstorm plus some more on the Add-On cards (AriadneII, Melody, CV64) were sufficient to keep the machine running.

Based on your descriptions, I'd check for bad solder joints on the Daughterboard connector (plus the connector itself) and hair fractures in the mainboard first.

Zack · 08 August 2016, 18:31

Thank you for advice buggs!

I will have the possibility to test my machine with a known working daughterboard this week, to find out if it's indeen the board itself, or the connector/solder joints on the motherboard. Then I will find out what to do.

Will have your advice in mind when taking my Amiga to a local repair guy.

Will post an update hopefully by the end of the week

buggs · 18 August 2016, 23:25

Good luck. I'm in the process of restoring some A500s to working condition to put less strain on the A4k once the Vampire lands.

11 October 2010, 11:07	#1
Cosmos Banned Join Date: Jan 2007 Location: France Posts: 655	Help for saving this A4000 zz Last edited by Cosmos; 16 July 2011 at 18:44.

07 August 2016, 20:29	#7
buggs Registered User Join Date: May 2016 Location: Rostock/Germany Posts: 132	Bad caps on the Daughterboard thoughts Well, I doubt that standard issue recapping is the way to go for that Daughterboard of yours, although replacing old caps is never a bad idea. The Daugtherboard features some Pullups and some Power stabilizing for attached cards but if there is nothing shorted on your board, the issue is quite likely somewhere else. I just recapped my A4k, where nearly every electrolytic capacitor had spilled its guts out. The Daughterboard was unaffected, btw. (due to standard issue axial caps instead of the dreaded SMD ones) Interestingly, the Amiga seemed to work fine for quite some time (despite the condition of the caps). Only after it started to develop sound issues, I recently did the rescue (originally planned for the winter). Bottom line in my case: Most of the caps were gone and still, the tantalums on the Cyberstorm plus some more on the Add-On cards (AriadneII, Melody, CV64) were sufficient to keep the machine running. Based on your descriptions, I'd check for bad solder joints on the Daughterboard connector (plus the connector itself) and hair fractures in the mainboard first.

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11 October 2010, 13:59	#2
Loedown Precious & fragile things Join Date: Feb 2009 Location: Victoria, Australia Posts: 1,946	Bust out your oscilloscope, check clock signal to all GFX chips. It looks like a timing fault, check the logic hardware around Lisa and also possible leaky diodes D504 etc. Video out connector, look for breaks where the connector pins right angle.

11 October 2010, 18:32	#3
Zack Registered User Join Date: Feb 2004 Location: Valby, Denmark Age: 48 Posts: 90	It's my A4000 that Cosmos is trying to save The AGA output went from working fine to totally dead in about 2 days. In between it became gradually worse. Right before the output went dead, I remember being able to boot with no Startup-Sequence to a WB screen that was relatively fine. But when dragging the screen 1/5 or more down, the output became something like in the video. Dragging it back up did not make it go away again. After a reset -> boot with no Start-Sequence I could do the same again. Later that day the output completely disappeared totally. Had the same graphics corruption on both the 23 pin connector, and on the output from my Indivision AGA. So I think that the video connector might be ok?

11 October 2010, 20:34	#4
Cosmos Banned Join Date: Jan 2007 Location: France Posts: 655	I put some new soldering on all diodes and on all Alice's connectors ! Seems to work all the time now Thanks a lot Loedown ! Maybe some micro-cracks like the 68000 on the A600 (http://eab.abime.net/showthread.php?t=55059&page=5) I'll keep this Miga 2 or 3 days for more tests...

12 October 2010, 06:20	#5
Loedown Precious & fragile things Join Date: Feb 2009 Location: Victoria, Australia Posts: 1,946	What do I win and where can I collect Cosmos? Odd graphic faults like that are going to be because of fluctuations in the video path that can be caused by timing faults and leaky trx / diodes if all caps are done.

04 August 2016, 14:05	#6
Zack Registered User Join Date: Feb 2004 Location: Valby, Denmark Age: 48 Posts: 90	Better a late reply than never! Started to do some systematic diagnose on my A4000 today, and have concluded that as long as the A4000 daughter board is attached to the computer, use of native graphics output is very unstable, and will either lead to a black screen, or graphics corruption followed by the computer hanging. Removing the daughter board, and the machine is stable when using native graphics. However using CGX graphics modes with my CV64 card, attached to the same daughter board has also been very stable for hours at a time, until I started using a native graphics mode (by starting a game or demo with WHDload). I assume that the daughter board might need to be recapped, but have asked a local Amiga group, if anyone have a working daughter board for me to test, to confirm my findings. Just wanted to share an update on the trouble, and a possible solution

08 August 2016, 18:31	#8
Zack Registered User Join Date: Feb 2004 Location: Valby, Denmark Age: 48 Posts: 90	Thank you for advice buggs! I will have the possibility to test my machine with a known working daughterboard this week, to find out if it's indeen the board itself, or the connector/solder joints on the motherboard. Then I will find out what to do. Will have your advice in mind when taking my Amiga to a local repair guy. Will post an update hopefully by the end of the week

18 August 2016, 23:25	#9
buggs Registered User Join Date: May 2016 Location: Rostock/Germany Posts: 132	Good luck. I'm in the process of restoring some A500s to working condition to put less strain on the A4k once the Vampire lands.

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