Amiga 4000 boots and works on RTG but black screen on AGA

[Reflex]

Hello

i hava an Amiga 4000 desktop inside a microbic tower with a CyberstormPPC improved by statchu100.
IT has a ZZ9000 and two more grafic boards on the mediator (a voodoo 3 and a Radeon 9200).
Now the problem is that the computer boots up nicely with RTG modes, but i cannot get any display on AGA modes, i cannot get any Early Startup menu too.
Id i unplug mediator and all the boards the screen starts low grey then light grey, the floppy stars clicking but i don't get the purple screen that invites me to put a floppy inside.
If i boots with floppy inserted it loads workbench (i can hear the noise) but the screens stays black.

It looks like the computer works but there is some kind of problem with the chips or memory, everything worked fine until a few time ago.
Am i right?
What did happen?

[Boing-ball]

What connection are you using for the native Amiga screen mode? (AGA). RGB 23pin connector? Or are you using a Scandoubler/Flickerfixer connected to the Lisa chip?

I do know the ZZ9000 with the video adapter port board should display a standard native Amiga display.
Has the Mainboard been recapped?

[Reflex]

MoBo is recapped.
ZZ9000 has a scan doubler yes and the amiga is conncted on the SCART port of the tv too.
So i'm sure that there is no AGA output at all.

[Boing-ball]

So from what you describe. I’m thinking it’s something to do with the video side of things. I wouldn’t think it’s Kickstart or RAM or even CPU. Why? As you describe things seem to be working in the background, such a floppy disk appears to be installing workbench.

Have you tried completely stripping down the A4000 to just the Mainboard only? Even taking out the Daughterboard/zorro 3 board?

Then just plugging in a RGB to SCaRT to see if you get the kickstart screen.

[cehofer]

Do you have clock battery damage?  If so, it can destroy the trace that tells the OS you have AGA.  If memory serves there is a trace that goes back to the ROMs.  I had that get damaged on one of my a4kDs

[Reflex]

Have you tried completely stripping down the A4000 to just the Mainboard only? Even taking out the Daughterboard/zorro 3 board?
Then just plugging in a RGB to SCaRT to see if you get the kickstart screen.

yes i did, same result.

I tested the MoBo with the diagrom and now i noticed that RBG test fails most of the time

[arttu80]

I think you should really do some continuity checks around battery on pcb.. Especially on U976 chip to pinpoint no AGA situation.
Check out http://wordpress.hertell.nu/?p=255 and http://www.amigapcb.org/#

[cehofer]

That battery leaking corrosion is like a cancer.  The board may work fine for several years but then start acting flaky.  I had one A4KD loose the mouse on the "Y" axis, RTC and AGA.  I had to lift the 3 chips off near the battery, clean and fix the board and then solder in new chips to fix the issues.  Loosing the mouse "Y" axis was the weirdest one.

Now, I have my original A4kD with no battery damage will not find the real time clock until a reboot.  After that, then it saves it just fine.  It started doing that out of nowhere.  I have the coin battery mod on that one too.  I may have to replace the 3 chips on that one too.  I will see how it progresses.

What I have seen the battery corrosion do is it like to eat off the head of the pass through of certain board traces.  Then as time passes, it must damage the chips.

[Reflex]

i bought this A4000 back in 2000 and the previous owner already removed the battery replacing it with a coin shaped one.
then it broke down during a storm and it was stored in a closet. After several years i decided to send it to repair to Hese in finland and found out that it was the SuperBuster burned by the storm, the MoBo was then recapped and worked fine.
So it cannot be a corrosion issue due to battery leaking.
Anyway ad far as i'm understanding there is some problem with the custom chips themselves or tracks

[Boing-ball]

Any of the chips in sockets? If so try pushing down on them or lift out clean with contact cleaner or similar and then replace. Could be as simple as that.

[Reflex]

only Super Buster and some GALs as i installed the 112mb hack

[Boing-ball]

I see you are asking the same questions over here as well:

https://eab.abime.net/showthread.php?t=116568

What you have failed to mention on this thread you are getting AGA now and again. This to me looks to be a connection fault on the board. Possibly a broken trace or a faulty component with a dry solder joint.

I have come across when boards have been fitted in the A4K case, where if the board flexes or it’s grounding on metal where it shouldn’t, where these issues can occur.

As a tip. Ignore kin_hell as he hasn’t a clue…