A2000 Rev. 6 not booting

[roadrash]

I have a Amiga A2000 that has stopped starting up. The power light comes on and but it doesn't go any further. Its had the usual battery leakage but I managed to get it all cleaned up and checked all contacts on the CPU socket. I fitted a new 68800 processor as the original had one bad leg. Ive also removed the kickstart and fitted a diagrom.
I am baffled as Ive checked all contacts on the processor socket and they are all good.
I have also checked all the contacts on the processor to the kickstart rom socket and all are making a connection except pin 12 which seems to be isolated.
The connections are as follows:
Can anyone tell me if these are correct or if there is something I am missing

Kickstart-socket CPU socket

1-------------------51
2-------------------61
3 ------------------62
4-------------------63
5-------------------64
6-------------------32
7-------------------31
8-------------------30
9-------------------29
(10-----------------16)
(11-----------------16)
12----------------- n/c
13------------------5
14------------------36
15------------------4
16------------------37
17------------------3
18------------------38
19------------------2
20------------------39
21------------------60
22------------------59
23------------------58
24------------------57
25------------------56
26------------------55
27------------------54
28------------------53
29------------------52
30------------------48
31------------------44
32------------------43
33------------------35
34------------------42
35------------------34
36------------------41
37------------------33
38------------------40
39------------------1
40------------------48

[Vypr]

Pin 12 of the ROM is the ROM_EN (ROM Enable) line and should be connected to pin 21 on Gary and pin 9 on U900

[Vypr]

If it will help, I've just uploaded the PCB Layout and schematics for the Rev6 to Githubin KiCAD format

https://github.com/iansbremner/Amiga-2000-KiCAD.git

[Malakie]

First thing you should do is remove any and all boards and use a simple floppy to boot with while troubleshooting this.

Second, reseat all Amiga chips just to make sure they are properly socketed fully.

Third, remove the upgrades you did if possible and reinstall the basics again and see if the system boots. If it fails, you may have something that has failed on the board itself.. cap, ram chip, etc.

If you can get it to boot by going back to the basic chips, then you have a starting point.

[roadrash]

Originally Posted by Vypr

Pin 12 of the ROM is the ROM_EN (ROM Enable) line and should be connected to pin 21 on Gary and pin 9 on U900

Thanks for that info and can say pin 12 of the kickstart Rom does connect to pin 21 of Gary as you say but I dont get a connection to pin 9 of U900 but do get a connection to pin 13 of U900.

[roadrash]

Originally Posted by Vypr

Pin 12 of the ROM is the ROM_EN (ROM Enable) line and should be connected to pin 21 on Gary and pin 9 on U900

Not familiar with KICad but have installeed it on my Linux laptop. Which of all these files in the directory is the actual Schematic?

[roadrash]

Originally Posted by Malakie

First thing you should do is remove any and all boards and use a simple floppy to boot with while troubleshooting this.

Second, reseat all Amiga chips just to make sure they are properly socketed fully.

Third, remove the upgrades you did if possible and reinstall the basics again and see if the system boots. If it fails, you may have something that has failed on the board itself.. cap, ram chip, etc.

If you can get it to boot by going back to the basic chips, then you have a starting point.

Thank you for that. The only thing connected to the bare motherboard is the PSU, floppy drive and the power LED. I can take out the diagnostics rom and put the kickstart Rom back in but otherwise its a pretty basic system.

[Vypr]

Originally Posted by roadrash

Not familiar with KICad but have installeed it on my Linux laptop. Which of all these files in the directory is the actual Schematic?

Amiga2000-R6.kicad_pcb is the board layout
Amiga2000-R6.sch is the schematic

[Malakie]

Originally Posted by roadrash

Thank you for that. The only thing connected to the bare motherboard is the PSU, floppy drive and the power LED. I can take out the diagnostics rom and put the kickstart Rom back in but otherwise its a pretty basic system.

Did you remove the diag rom, install the original and insure that is not the problem?

If the swapping the kick start does not work, it is likely one of three possibly issues:

1) power supply is dying or not supplying proper voltages
2) something is literally ON or under the mainboard that is shorting something.. a piece of metal, a screw or some type debris that somehow fell onto the board and is now shorting between to spots.
3) a chip failure. Possibly one of the 8520's or worse, a ram chip was spiked.
4) a board component failure, cap, transistor or even a pathway is open.

Also, make sure no pins are touching on any of the zorro II slots, i.e. pulling a card or something did not bend anything visually you can see.

You said it was working and then not. Was it working one moment and the next time you turned it on, it just stopped working? Or did you change anything between power off or power on that time? i.e. added a card, a drive, removed a card, etc?

I have been restoring a couple A2000's that were bad. I have them both running now and as it turns out, the first one had debris shorting it. The second one was a bad card AND a bad chip. The second I had working well when suddenly it wigged out and would not boot and started displaying lines for video on the monitor on power on. I had simply installed a ram card. I removed the card, plugged it in again and the new problem disappeared.

So you have to go back to the moment it failed and start troubleshooting forward from that. Try to think of EXACTLY what you did and like I said, if all you did was turn it on, then something failed at that moment.. power supply, a chip just finally gave up the ghost, or some other component died.

[roadrash]

Was it right then that pin12 of kickstart socket connects to pin 13 I'd U900?

[Vypr]

Originally Posted by roadrash

Was it right then that pin12 of kickstart socket connects to pin 13 I'd U900?

Only if U900 is upside down. Pin 13 on U900 should be connected to 5V

[roadrash]

Originally Posted by Vypr

Only if U900 is upside down. Pin 13 on U900 should be connected to 5V

Interesting will check that again.

[roadrash]

A while ago I did a ReCap and now wondering if something there is causing trouble and now checking all again.

[amiman99]

I had a battery damage on my A2000, black screen and nothing else.

To fix it, I reflowed the solder on all surrounding area, and replace the cpu socket.
Worked fine after that.

[roadrash]

Originally Posted by amiman99

I had a battery damage on my A2000, black screen and nothing else.

To fix it, I reflowed the solder on all surrounding area, and replace the cpu socket.
Worked fine after that.

I did think about the socket but when check it all connections are being made. I might as well replace it as cant find much else that's wrong.

[roadrash]

Originally Posted by Vypr

Only if U900 is upside down. Pin 13 on U900 should be connected to 5V

Just checked and yes there is just under 5v at pin 13 of U900. I will order a new processor socket just to eliminate that too.

[roadrash]

The only connector on the mc68000 socket that was slightly corroded was pin 1. I cleaned that one up and it is showing a good connection to the motherboard. I really cant see changing the socket will achieve anything even though I've ordered one. When I turn it on the screen stays black and if I leave it on all the chips are warming up as you would expect them to do. Is there anything else I can check??

[jasonsbeer]

There are a great many things that can cause a black screen. You mentioned diagrom. Do you get any serial output from it? Even with a black screen, you will often get data on the serial port from diagrom. If you get nothing on the serial port, that alone will tell us a lot. Otherwise, it's just guessing.

[roadrash]

Originally Posted by jasonsbeer

There are a great many things that can cause a black screen. You mentioned diagrom. Do you get any serial output from it? Even with a black screen, you will often get data on the serial port from diagrom. If you get nothing on the serial port, that alone will tell us a lot. Otherwise, it's just guessing.

Ok I hooked the amiga up to my pc with a serial cable and null modem and used PUTTY but when I turn on the amiga there is nothing. I tried using linux & windows but same thing.

[Malakie]

I have been working on restoring a couple Amiga 2000's here as some know. The black screen can be caused by a whole lot more than just a bad chip or component.

For example, I got one of these boards working. Then yesterday, in fact, I was working on that unit and right in the middle of testing it, I got it to boot to Workbench when suddenly the screen went black.

At first I thought something I repaired failed. As it turns out, it is the power supply that just finally gave up the ghost. It has enough power to turn on the power LED, make the fan go, even cycle the floppy drive. But the screen never turns on. I used another power supply and this board is finally repaired but now the power supply has failed so now I have to fix that too.

The other board also has a black screen that I will be repairing soon. However that problem came from a power feedback through the floppy drive and a gotek drive that blew out while using it that I had connected externally. It blew the pico fuses and fed into the floppy drive itself. The machine again black screen. Even after I replaced the pico fuses, the machine refused to move from a black screen... UNTIL I unhooked the floppy drive. Once I unhooked it, the machine powered up again properly.

So the problem could be a myriad of issues and you need to think outside the box with Amiga systems. I am slowly getting back to my level of knowledge from 30 years ago, which helps greatly being I was a Commodore Technical Engineer back then. But even I make mistakes and am still re-learning much of what I knew 30 years ago.

I would start from scratch. Test the power supply and go from there.