Macintosh Plus - error 01204E

[drg]

Hi,

I got Macintosh Plus with broken floppy disk (currently it's disconnected). Unfortunately after powering on I got 01204E error. The keyboard is not connected (I should have tomorrow one). I tried to boot from BlueSCSI, but still the same error occurred (Macintosh SE FDHD and Classic booted from BlueSCSI just fine). Can somebody drop mi a hint?

Best regards,
Pawel

 

[drg]

I found some info, that it could be due ROM problems, I ordered new chips and will try to flash new ROM next week.

 

[VERAULT]

keep us posted.

 

[drg]

Success! That was it.

I ordered two of W27C512-45Z, unfortunately one of them had broken leg. However I dumped two original ROMs and then downloaded 3 version of ROMs for Macintosh Plus. Next I split those ROMs into HI and LO parts and then I calculated MD5 sums for all halves. As I suspected, one original ROM (actually half of ROM) matched to one version of downloaded ROM (the newest one). The second halves had other MD5 sums, so I knew which half I had to program and replace (of course, if I had 2 working W27C512-45Zs I wouldn't be doing these comparison and just burn the newest rom to new chips). After replacing mismatched half of the ROM, the Macintosh Plus came to life.

The next step is to make keyboard cable. Unfortunately, at first I connected normal RJ9/RJ10 telephone cable which is not crossed, so +5v from the computer went to GND on keyboard side and vice versa. I hope it didn't kill the keyboard, I will make the proper cable this week, probably.