Amiga 4000 Rev. B - does not boot - black screen :-(

[nicolas]

Hi all !

I am working on a "dead" Amiga 4000 Rev. B mainboard for 2 weeks now. It suffered some battery and capacitor damage, but it meanwhile looks like a new one; but unfortunately still not booting into Kickstart screen.


-------------------------------------------------------------------------
Here's a list of what I have done with the mainboard so far:
-------------------------------------------------------------------------

1.) Desoldered most of the ICs, resistors and ceramic capacitors around the leaked SMD electrolyt capacitors and the battery area and checked and repaired all traces where necessary and replaced the ICs and other parts with new ones.

2.) I also replaced all SMD electrolyt capacitors with hybrid polymer ones from Panasonic. I also replaced U891, U177, U975, U976, U403, U404 and U178 (RTC IC). Later I also checked and replaced U455, U456, U457, U458, U205, U710 and U131 (desperate brute force attempt ).

3.) Meanwhile I have also desoldered and socketed almost all custom chips, in order to check their functionality with another, known working, mainboard (where custom chips are socketed as well). ALICE 391010 got hot and I have found out, that it's defective. I am now testing with the known working ALICE from the second mainboard.

4.) I am using a A3640 accelerator for testing. I know it's 100% working, tested on the second mainboard. I am also 100% sure that the Kickstart ROMs and Chip RAM is working fine (tested on second mainboard and also because DiagROM boots fine; cp. further below).

5.) I re-soldered almost every soldering joint on the backside with flux and some new solder.

6.) The lowest Fast-RAM socket is currently missing. Had to repair the well-known traces below it. Will replace it with a new one.

7.) I tested the CIAs U300 and U350 on second mainboard. They should be fine. Also swapped Paula U400 in order to determine if it's working. Should be fine as well.

8.) I polished all contact of all custom chips with a glass fiber pencil.

9.) I cleaned the CPU socket and the 6-pin power connector with contact spray and a tooth brush.

10.) Working with a revised power supply unit: +5V -> +4.95V; +12V -> +11.85V; -12V -> -11.82V


-------------------------------------------------------------------------
This happens when trying to boot with normal Kickstart 3.1 ROM:
-------------------------------------------------------------------------

A.) Normal power on -> dark grey screen -> light grey screen -> nothing more happens (always waiting for around 45 seconds).

B.) When removing Chip RAM and powering on -> usual green screen (so Chip RAM sockets and Kickstarts should be fine).

Here's a video I made: https://www.youtube.com/watch?v=sRyo0-Tc5q4&feature=youtu.be


-------------------------------------------------------------------------
When using Chucky's DiagROM v 1.2:
-------------------------------------------------------------------------

The Amiga boots into the DiagROM menu. Most of the test do work, BUT the CIA and IRQ tests fail! However, the new experimental CIA test in DiagROM's version 1.2 gives some results (cp. video).

1.) Video of failed IRQ test: https://www.youtube.com/watch?v=E-_YC_poeA0&feature=youtu.be
2.) Video of failed CIA test: https://www.youtube.com/watch?v=RwTJ41kqOJg&feature=youtu.be
3.) Video of experimental CIA test: https://www.youtube.com/watch?v=ZUHrVh_eQ9c&feature=youtu.be

Furthermore I have connected the faulty A4000D mainboard to a working A3000D serial port using a null-modem adapter. When booting and reading the DiagROM's output, it first runs fine and it prints some information to the terminal. Then it stops at the line:

Code: [Select]

Testing if serial loopbackadapter is installed: <> DETECTED... here the output freezes.

Here's a screenshot, after the last line, it does freeze and gives no more output.

When using the working A4000D mainboard, I get the full output and the above line reads:

Code: [Select]

Testing if serial loopbackadapter is installed: <> NOT DETECTED"which is fine; since in both cases I am using exactly the same setup, namely:

Code: [Select]

A3000D serial port <-> serial cable <-> null-modem adapter <-> A4000D mainboard's serial port

-------------------------------------------------------------------------
Some high resolution images of the mainboard
-------------------------------------------------------------------------

Here are some high resolution images of the mainboard (at some points there's some flux residuals, especially on the backside; not yet cleaned up):

Faulty Amiga Mainboard (Image 1/7)
Faulty Amiga Mainboard (Image 2/7)
Faulty Amiga Mainboard (Image 3/7)
Faulty Amiga Mainboard (Image 4/7)
Faulty Amiga Mainboard (Image 5/7)
Faulty Amiga Mainboard (Image 6/7)
Faulty Amiga Mainboard (Image 7/7)


-------------------------------------------------------------------------
Devices available & conclusion so far
-------------------------------------------------------------------------

I have a good multimeter device and a Saleae Logic 16 analyser in case somebody can give me some instructions what signals to test.

Studying the custom chip assignments, this would point to an issue with either the CIAs or the Paula IC, correct? I checked everything in these areas... No more ideas.

Any help and ideas highly appreciated - I am really desperated ... 

[arttu80]

Wow, that's some serious work you have done with this motherboard repair!

I am no expert or anything close to it but just out of curiosity, is it anyhow possible to system hang on bootup if Buster chip went busted? I mean some of its pins are connected to CPU slot afterall, which theretically can mess it up? It's funny that's only chip on your motherboard that still remains soldered without socket.. Which is just opposite of mine Rev.B which had Buster rev.9 in the socket, and I just pop it out and rev11 went in.. All other chips aren't socketed.

Offtopic, I'm struggling to get my RTC back to life..

https://forum.amiga.org/index.php?topic=74685.0

I wish you good luck with your A4000 "adventure"!

[matt020]

I'm no expert, but when reading your post, my gut feeling was : Buster.