Amiga 2000 / A2091

[acadiel]

I have an Amiga 2000 that I inherited that I'm cleaning out to make it ready to donate to some Amiga user.

It has an A2091 inside (fully populated with DRAMs).  However, when the 2MB setting on the A2091 is set, I get a yellow screen on boot, and the red light flashed bright/dim.  If I move it down to 0MB, the system uses the onboard 512KB chip/512KB fast RAM and does boot from the 2091's hard drive.

Any way to troubleshoot this?  Do any vendors still sell these things to swap them out?  Any way to test them?

Thanks!

[amiman99]

I would try to check RAM chips 512KB at a time, maybe one of your RAM chips are bad. Set the jumper to 512KB, start the computer and see it it works, if it does then try 1MB, you can try with the chips inserted or remove them all and try 512KB at a time.
Also, do you have any other RAM board installed?

[acadiel]

I would try to check RAM chips 512KB at a time, maybe one of your RAM chips are bad. Set the jumper to 512KB, start the computer and see it it works, if it does then try 1MB, you can try with the chips inserted or remove them all and try 512KB at a time.
Also, do you have any other RAM board installed?

Yep, did that... it did the same thing at 512K, and 1MB.  The only jumper that apparently works is 0MB.

No other add on cards; it's a stock A2000 with just the A2091.

I had three A2000's given to me, and I've been working through them to get some workable systems.  So far, I have:

A2000 (stock 512K chip/512K fast) with A2091, unknown (haven't checked) SCSI drive, WB 2.04.  One floppy drive; inoperative.  Front cover has three screw stands broken on it; I need to see if I can epoxy them back.  Someone hacked the PSU and cut off one of the Molex connectors.  Has an additional SCSI drive that came with it, but it wasn't hooked up.  Haven't tried it yet.  No keyboard/mouse.

A2000 (has 2MB chip ram mod) with GVP 68030 (33mhz?) accelerator/SCSI and 16MB RAM card installed with 3.5" SCSI hard drive in bottom bay.  Two floppy drives; both inoperative.  PSU good, case is good, need to get additional screws for it.  Cleaned up the case (scrubbed it real good), so the only real problem with this one is it needs new floppies and some screws.  Keyboard and mouse.

A2000 (has 2MB chip ram mod) with 68040/25 accelerator/SCSI and a crapload of RAM (haven't done an avail on it yet) with attached 3.5" SCSI hard drive on the back of the accelerator.  Has flicker fixer in video slot with VGA connector.  Also has a PVR card (records video, encodes with JPG/MPG?).  PSU good, case is good, have all the screws.  Cleaned up the case.  One floppy drive, seems to work OK, but was touchy until I cleaned it.  Keyboard with Toaster stickers on it and mouse.  Intermittently booted up with green screen, but I reseated Agnus and the pin that went to Gary (I think) and it is happy again.

Also have six TBC cards, five with passthroughs, and a Video Toaster 2000.

I probably will keep the 68040 system but the rest will be fair game.  If I six the floppy drive issues by getting refurbs from Software Hut, I'll just tack it onto the price (one I'm probably giving away, the other two likely will be sold), or let whomever is going to be getting this buy the replacement and swap it out.  I hooked an external floppy up to make sure the floppy controller was working on all three.

There was lots of dirt, grime, cigarette smoke, etc, on these, so it's been a labor of love fixing them up.

[acadiel]

Still no luck with the A2091, but got all the defective floppy drives replaced!

http://eab.abime.net/showpost.php?p=808023&postcount=198

[acadiel]

Still no luck with the A2091, but got all the defective floppy drives replaced!

http://eab.abime.net/showpost.php?p=808023&postcount=198

Hey guys -

Are these the drams I need to buy to try and get this working?

http://www.arcadecomponents.com/catalog/item/2251646/1691189.htm

[amiman99]

Hey guys -

Are these the drams I need to buy to try and get this working?

http://www.arcadecomponents.com/catalog/item/2251646/1691189.htm

Looks like they are the correct ones, BUT I don't think that ALL your DRAMs are bad, it could be the board. I have one of those A2091s and it has the same problem, it doesn't recognize the RAM.

[Zac67]

Don't think all RAMs got bad at the same time either... Try removing everything but four RAM chips & set the jumper to 512K. If that doesn't work, replace the RAMs with another set of four. If both sets don't work at all, it's probably the 2091 that's faulty. But my guess is on the first 512K being bad (i.e. one of the chips in the first set).

[Methuselas]

Yeah, try swapping it to another Zorro slot too and see if it works. I used to have a rev 4.3 mobo that was flaky as hell. Wouldn't use an accelerator to save it's life and only certain cards would work in certain slots. I ended up stripping my derringer from my old a500, and throwing it in my 2000, 'cos it was the only way I could get it accelerated.

[shaf]

The accelerator problem on the A2000 Rev 4.3 can be solved by adding a 3.3K Ohm resistor between pins 11 and 20 on U605 (74LS245) located beside connector CN 600 9 - 86 Pin expansion connector).

[Methuselas]

The accelerator problem on the A2000 Rev 4.3 can be solved by adding a 3.3K Ohm resistor between pins 11 and 20 on U605 (74LS245) located beside connector CN 600 9 - 86 Pin expansion connector).

That would have helped me back in 1997..... ;P

[acadiel]

Looks like they are the correct ones, BUT I don't think that ALL your DRAMs are bad, it could be the board. I have one of those A2091s and it has the same problem, it doesn't recognize the RAM.

Well, I know the SCSI part works.  

So, if I try this and it still doesn't like the RAM, any ideas which ICs I might try and replace? :-)

http://www.amiga-hardware.com/download_photos/a2091_2_big.jpg