Amiga 4000D, when gets warm AGA graphics dropout to black.

Hello eveyone, I'w been reading and having found much nice information and laughs here at the forum, now I'w registred and this my first post here;


I'm fixing my Amiga's to usability (software wise =).
But now I have ran into some strange phenomena, that feels hardware wise.

When the computer is booted it runs fine for a while, but after some time, and i guess its gotten warmed up.. the video output of the system dissapears.
If i reboot and go to the boot screen and leave the machine there, the mouse and the klickable boxes dissapear from visibility, BUT,
it is possible to press keys on the keyboard and I when done I can see what looks like the frequence changes of bootscreen PAL to NTSC toggle. etc. and caps lock seems reacting and beeing pushable ad finitum.
A warmreboot with keyboard works as well.
The system can even often (in this strange phenomenal stage) boot further into workbench, (hd lead flashes normally and ends where it should , thats what it 'feels like' but I cant see it, its a black screen, but with all the feeling of intuition and Workbench presence =)

With these symptoms i went on and exchanged almost ALL of the capacitors on both the A3640, and the motherboard itself.
(involving cleaning with alco. etc. before resoldering new ones)
BUT still the same symptoms, or maybe i felt a bit sturdier.. but well it still does the same symptoms.

-Computer System Info:
The system is an Amiga 4000 desktop. with the following lifesupport;
ATX psu, Layla Keyboard adapter, Coccolina Mouse adapter,
Battery removed y2000 and replaced recently (so should be no leak)

I have a Deneb, PicassoIV, Delphina DSP light, (and a Buddah) as Zorrocards to be used when / If I get it back to running smoothly.

16MB on-board RAM, Physical kickstart/workbench v3.0 (tough softed to 3.1 normally)
-

The replacement of the caps started after some troubleshooting with Michael from E3b, because of my Deneb USB card hanging when being used in DMA mode transfers. And the test computeres used for Deneb testing by e3b are running fine with this kind of machines in DMA, he suggested leaky caps, memerrors, battery..


;connected to a -
It's connected to a 1942 monitor, and the monitor has a little problem, it drops out the colours now and then (turning into nice green shade =), and a smack to the side ... makes it go normal.. But i dont think its screen related, but i might be wrong.

Could it be PSU related?
Well..
Anyone have some hints to what I might try to look at / replace

Regards and hopes..
And sorry for the not so Condensed post.. =)
and thanks for a very good Amiga Board where to find resources
/Kenneth

[alexh]

IS the gfx black on both the PIV AND the regular Amiga video connector??

Or do I take it the PIV has been removed?

If i reboot and go to the boot screen and leave the machine there, the mouse and the klickable boxes dissapear from visibility, BUT, it is possible to press keys on the keyboard and I when done I can see what looks like the frequence changes of bootscreen PAL to NTSC toggle.

Pressing space on the keyboard in KS3.1 Early startup menu toggles between NTSC and PAL. (Not sure if this is the same in KS3.0)

16MB on-board RAM

I think you mean 18MB. Could the Chip RAM SIMM be loose? Are the connectors broken on the SIMM slot?

hi alexh

Originally Posted by alexh

IS the gfx black on both the PIV AND the regular Amiga video connector??
Or do I take it the PIV has been removed?

I'm running, only the standard Amiga chipset output for now.
Haven't tried with the PIV, i could add it in to the equation and test if it runs on and on with that.

Originally Posted by alexh

Pressing space on the keyboard in KS3.1 Early startup menu toggles between NTSC and PAL. (Not sure if this is the same in KS3.0)

Yes, normally it works that way. So i think it must be responding with PAL/NTSC shifts.

Originally Posted by alexh

I think you mean 18MB. Could the Chip RAM SIMM be loose? Are the connectors broken on the SIMM slot?

Yes, sorry, 16 MB fast, 2 MB chip, all in 5 SIMM slots.

And I'w tried to run without even the ZIII doughterboard, but same situation there.


Oki i'll do a PIV install and try run that way, till it gets 'warmdup' =).

I'll post later.

Regards
/Kenneth

Ok now I'w put in the Picasso IV physically. The machine was all black from beginning, i was hoping it would run NONblack for some minutes so i get time to install the picassoIV drivers. But nope, and the monitor goes all wild and crazy flashing-rastering-colours-whining when goes into the multiscan resolution, not just black like it used to be. Ok... now goes, i tried to boot into earlystartup (knowing and hoping atleast it would work with the NTSC/PAL keyboardthing.) but nope. system just stands still... I reboot, shutdown.. and... after shutting off power of PSU again, and then try to put the PSU on. all power LED's of Amiga are non igniting and no harddisk noise and nothing booting, all that is reacting is a 5V fan i have connected to the PSU as an airsuck from the Desktopcase.

Hmm could it be ATX PSU failure magick
I wonder, Anyone know if failing (atx)PSUs can make an amiga act in this kind of madness? =)

Well hehe its fascinating tough.

/Kenneth