A4000 Tips for repair.

We must find all togheter a method to check and find the prob(s) on every Classics in 5 minutes...

I'm sure it's possible...

First, I'll picture all ICs and on each of them, take the pins voltage... Can be usefull... I'll begin on a working A4000D revB (y)


Any others ideas ?
 
Something is messing with the chip-ram data bus for you to get the green screen. Maybe one of the other chips that are connected to the chip ram data bus have a problem (Paula, Lisa, Alice). Check the reset lines, if any are stuck low all the time that may help isolate the problem. Check for normal activity on each of the 16 chip-ram data bus lines on an oscilloscope if you have one. I think they're labeled DRDxx on the schematics.
 
@Cosmos

If any of the customs is faulty, the FatGary dont start the reset lines.
The same can happen from any point of the machine with any other problem large or small. For example if you go to 74HCT166 one of two ic who is responsible for joy controllers, and cut the MDAT line, the machine doesnt boot at all.

For all this reasons I believe is not possible to make a list for defacto standard problems.

An other example is the RTC. If it is faulty, the machine can doing anything. In a previews repair, any time who I power on the machine, had a different screen. Yellow, green, red!?!?! One other time, was just dark grey.

Confused??:wooha:

---------- Post added at 01:08 ---------- Previous post was at 01:05 ----------

Also as Hikey said, (and I in previews post) check the reset lines.
 
We must find all togheter a method to check and find the prob(s) on every Classics in 5 minutes...

I'm sure it's possible...

First, I'll picture all ICs and on each of them, take the pins voltage... Can be usefull... I'll begin on a working A4000D revB (y)


Any others ideas ?

you got still green/gray/green

have u change the video DAC chip U460 , thats a chip that give also a green screen

when i not work , maybe i can check you board , i got 2 roms here to check the memory chip/fast data lines cia ( timer datalines ) audio , video datalines
 
I give up with this board for the moment...



I have another A4000D :

No boot at the beginning with an A3630 (n)

I put the Ricoh on socket, this one seems to work...
So, I changed U891 and the A4000D boot ! :D

But, the Amiga boot only with 2 Mo of chipram...
When I put 8 Mo (2 x 4) : no boot, the screen flash...

My fastmem is good for sure.

When I put a CyberStorm MK I 040, the Amiga boot fine and my 8 Mo fastmem are ok under the Workbench ?!
(I will try without fastmem on the MK I tomorrow)

Any idea to fix ??



And I can't save the date & hours : I must change U177 ?
 
Change the capacitors near the SIMM and the two TTL buffers near the SIMM sockets.
 
U707 and U708 changed... Still flashing and no boot...


Any other ideas ??

---------- Post added at 10:43 ---------- Previous post was at 10:42 ----------

I changed U177 : the date & hours are working now (y)

I tried with the MK I without Simms on it : no boot too...
 
You checked the address & data lines on the SIMM sockets traces? Chances are a trace get corroded away (normally under the SIMM socket nearest of the battery).
 
Aaaarrrrgggghhhhh...


Another A4000D : no boot !

I changed U891, and the A4000 boot fine, but only with 1 Mo of Chipmem !! :Doh::Doh::Doh:

The fastmem is ok : 8 or 16 Mo... It's only the Chipmem...

I tried with three 2 Mo : always only 1 Mo on the WB...


Any ideas to fix ??
 
I have discovered how to use a 4Mb SIMM as replacement of rare factory SIMM. Just change J213 to 2-3 position and J214 to 1-2 position. This have cured, in my case a strange problem after fews minutes of working: rapid flashing green and yellow.

Now it works very well. Hope this can help someone.
 
I have discovered how to use a 4Mb SIMM as replacement of rare factory SIMM. Just change J213 to 2-3 position and J214 to 1-2 position. This have cured, in my case a strange problem after fews minutes of working: rapid flashing green and yellow.

Now it works very well. Hope this can help someone.

Did you mess with the "free sex & beer" jumpers?:wooha:

And they work for something?:blink:
 
A4000 Rev B - no picture signal

A4000 Rev B - no picture signal

Trying to repair A4000 Rev B that gives no picture signal at all. I mean not even that dark grey screen that happens when I remove CPU card and SIMMs from another working A4000 Rev B.


  • PSU is ATX that works with 2 other A4000 motherboards
  • Main voltages seem fine.
  • Have checked everything that is socketed in another A4000 Rev B (including two oscillators that are pin socketed in every A4000 Rev B - did not know this before :wooha:)
  • Desoldered and measured all electrolytic capacitors with capacitor meter and replaced some.
  • Measured all diodes.
  • Socketed all DIP ICs and SUPER BUSTER and tested them in another A4000 Rev B
  • Some old battery leak marks, but have seen many that were looking more serious and still caused nothing this severe.
Any ideas where to continue?

Would you risk trying with valuable Picasso IV and or Mediator to see if it is just the display circuitry and nothing else?

Got about 30 pieces of new 68 pin PLCC sockets. Which one would you socket next Alice, Lisa, Fat Gary, Ramsey...?

Are A4000 motheboards multilayer PCBs or is there just upper and lower side and nothing else? If multilayer, then reinforcing vias (trace holes) is a no go.

Any tip is appreciated. This troublemaker has been under work for almost a year soon. :tired:
 
They are 4 layer. reenforcing the vias is fine.

Apparently the middle 2 layers are power and ground. But any vias will have space around them in the middle layers.


Sent from my iPhone using Tapatalk. Please excuse any crazy auto corrects or lack of detail (links to info sources)
 
what could be the reason that an A4000D board goes straight into the reset loop after you turn it on (screen for short dark grey)? Power LED is flashing.

as info: unfortunately I didn't place the board properly in my desktop case for testing and R79 got ground contact. The conductor path is still intact and R79 still have 1.2k.

I removed as a quick test the chipram and the screen goes as expected green. So the board is still doing something.

thanks for help.
 
another board with same defect, work with diag rom, but reset every 1 second, found "has cut the line between R79 and his hole" soldered a wire, and now work fine
 
Last edited:
Reviving a useful thread to add some more info:

R79 trace to via was also causing weird behaviour on a 4000D system that came by me... it wasn't completely broken but very high resistance.

The symptom was the system was fine for the first few minutes on a completely cold boot but then would enter a reset loop/reboot loop through black/grey screens. Alice was very hot. Fixing R79 trace completely fixed it.
 
Back
Top Bottom