PBOURKE%IRLEARN.BITNET@cunyvm.cuny.edu (P Bourke) (02/07/89)
I have an A2000 (not B2000) which has the following problem: When I power off and then on again the machine freezes with the power light dim, if if I unplug the keyboard the system starts up as normal, it also does so with no keyboad present. I have tried another keyboard and the same problem happens. Therefore I assume some component has gone on the motherboard - any suggestions? Also on the subject of A2000's. What PRECISELY am (will) I missing out by not having a B2000? i.e. will the CBM 68020 board function correctly, the RAM board and also the new 1MB chipset Thanks in advance for any help
daveh@cbmvax.UUCP (Dave Haynie) (02/08/89)
in article <8108@louie.udel.EDU>, PBOURKE%IRLEARN.BITNET@cunyvm.cuny.edu (P Bourke) says: > I have an A2000 (not B2000) which has the following problem: When I power > off and then on again the machine freezes with the power light dim, if > if I unplug the keyboard the system starts up as normal, it also does so > with no keyboad present. > I have tried another keyboard and the same problem happens. Therefore I > assume some component has gone on the motherboard - any suggestions? The chip that's responsible for reset is an LM2901 on the A2000 motherboard, at U20. If that chip is going bad, you might see some kind of similar reset problem. The only other IC that's involved at all is the 8520 CIA chip that actually drives the keyboard; this is U10 on the PCB. Once you've removed the power supply/disk assembly, you can easily swap the two 8520s (the other is U11). This would at least rule out an 8520 problem is it doesn't fix the condition. The synchronous serial port that drives the keyboard isn't normally used in the other CIA, so you'd be able to run your system just fine with that port bad in one chip. > Also on the subject of A2000's. What PRECISELY am (will) I missing out by > not having a B2000? i.e. will the CBM 68020 board function correctly, Yes, but you won't be able to boot up with the 68000 in charge -- the 68000 must be removed from the "A" board to use the A2620. > the RAM board Shouldn't be any difference in the 100 pin bus. > and also the new 1MB chipset You can't use the ECS chip set in the "A" board, that's the main disadvantage. Also, flickerFixer and similar devices won't work in the smaller "A" board video slot. > Thanks in advance for any help -- Dave Haynie "The 32 Bit Guy" Commodore-Amiga "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: D-DAVE H BIX: hazy Amiga -- It's not just a job, it's an obsession