Amiga 2000 Rev 4.3 - Only 0,5MB ram visible (0MB other RAM)

General hardware issues and troubleshooting etc

Moderators: terriblefire, Terriblefire Moderator

Post Reply
snifferman
Posts: 13
Joined: Wed Jun 03, 2020 9:57 am

Amiga 2000 Rev 4.3 - Only 0,5MB ram visible (0MB other RAM)

Post by snifferman » Sat Nov 07, 2020 4:22 pm

Hello,
I got A2000 after baterry lekage. I replaced CPU socket, ROM socket,RTC chip, fixed 2 traces near CPU. Amiga works now, but only 0,5MB chip is visible in DIAGROM or AmigaTestKit(no slow ram/other ram). J101 on position 1-2, J102-closed, J500-closed.

I swaped Agnus to 8372A(was 8371). J101 on position 2-3, J102-open, J500-open. Still only 0,5MB chip is visible. No other ram.
I have tested U540,U541,U103,U104,U105,U106,U900,U603 on my TL866 programer. All ok.
I swaped chips from A500 (2xCIA,PAULA,DENISE,AGNUS,GARY,CPU). No change

Amiga works. I have installed TF536 on it and started Frontier and Setllers form SD card. Works fine.
Why i can`t get 1MB CHIP or 0,5MB CHIP+ 0,5MB SLOW?

EDIT:
Forgot to say, that i tested with KICK1.3, Kick3.1

mobo.jpg
mobo.jpg (384.12 KiB) Viewed 326 times
bat and cpu.jpg
bat and cpu.jpg (454.38 KiB) Viewed 326 times
BAT region.jpg
BAT region.jpg (378.61 KiB) Viewed 326 times

Maximilian
Posts: 164
Joined: Thu Feb 28, 2019 5:02 pm

Re: Amiga 2000 Rev 4.3 - Only 0,5MB ram visible (0MB other RAM)

Post by Maximilian » Sat Nov 07, 2020 9:38 pm

That should work.

First question, did you have 0,5 MB chip and 0,5MB fast (ranger) ram to start with?
If yes, then please post closeups of the jumper areas
Make sure to measure the cuts you made to the jumper pads.

Have a look at this for the correct changes:
https://www.nightfallcrew.com/30/09/201 ... m-upgrade/

Only the 68000, Gary, Agnus and the ram are involved, changing anythig else is futile IMHO.

p.s. those are Sanyo LM33256G-15 chips?
(please look at them closely)

snifferman
Posts: 13
Joined: Wed Jun 03, 2020 9:57 am

Re: Amiga 2000 Rev 4.3 - Only 0,5MB ram visible (0MB other RAM)

Post by snifferman » Sun Nov 08, 2020 2:00 am

Thank You for replay.

I have the same board revision as on this movie and there is a ranger RAM visible and 1MB of chip after mod.


I can se only 0,5MB of chip. Before the mod and after.
I checked the jumper pads with multimeter after cutting and they are separated.
I traced J500 to GARY and after cutting _EXRAM is +5v. 0V if bridged so it works correctly
Memory chips are SANYO LM33256G-15

Someone has schematic for REV 4.3? I found only one for REV6 and there RAM is in different chips.
How Ram is Detected on AMIGA 2000? Maybe some traces are still bad and preventing detection of other 512KB?

a3.jpg
a3.jpg (169.57 KiB) Viewed 268 times
a2.jpg
a2.jpg (88.6 KiB) Viewed 268 times
a1.jpg
a1.jpg (139.08 KiB) Viewed 268 times

Maximilian
Posts: 164
Joined: Thu Feb 28, 2019 5:02 pm

Re: Amiga 2000 Rev 4.3 - Only 0,5MB ram visible (0MB other RAM)

Post by Maximilian » Sun Nov 08, 2020 1:39 pm

Take a look at this one for the schema:
http://tele-work.hu/Vas/Amiga%20500%20T ... erence.pdf

snifferman
Posts: 13
Joined: Wed Jun 03, 2020 9:57 am

Re: Amiga 2000 Rev 4.3 - Only 0,5MB ram visible (0MB other RAM)

Post by snifferman » Wed Nov 18, 2020 3:47 pm

One of the RAM chips was bad.

after replacing it, 1MB chip is visible and no errors in memory test.

Thx for help.

Maximilian
Posts: 164
Joined: Thu Feb 28, 2019 5:02 pm

Re: Amiga 2000 Rev 4.3 - Only 0,5MB ram visible (0MB other RAM)

Post by Maximilian » Wed Nov 18, 2020 8:24 pm

Nice find!
Thanks for letting us know :)

Post Reply

Return to “AMIGA HARDWARE HELP”