Since the video logic appears to be working, I would suspect the system ROMs. If you have already swapped them out, the next thing to look at would be the 2 74LS244 bus drivers for the ROMs. If you have access to a multichannel triggered oscilloscope, you can check them in circuit. Otherwise, you would have to replace them just to check the possibility. They seldom survive being unsoldered. On Fri, 1 Nov 2013, Ville Laustela wrote: > > Hello all. > > I posted the following thrue http://cbm-hackers.2304266.n4.nabble.com -site but that didn't seem to work (message shows on the website but apparently not in the mailing list itself) so I'll repost this now here. Sorry if this gets double-posted. > > -- > I had my PET-2001 with me at SAKU (Finnish Amiga Users group) 2013 meeting some weeks ago (photos here: http://koti.kapsi.fi/~myrjola/photos/digital/saku_2013/index.php) running a small BASIC- demo I made. After being running several hours without any problems, suddenly the machine halted. > > Since that all the machine gives out is a reversed ?- mark on screen (see here: https://www.dropbox.com/sh/90jl2zx2qi8lc27/uZUFNHoDJT). This appears identical in every boot. If I reset the machine (by quickly turning mains switch off and back on) I can see screen filled with random characters, then it blanks (like during normal reset) but goes to the ?-mark screen again. As you can see in the photo, most of the bigger chips have small heatsinks installed and all electrolytic caps on the board were replaced earlier. > > I have tried re-seating all socketed chips but still no go. Only chips running more than warm are the two MOS MPS 2114 chips (warm to touch but not as hot as fe. shorted RAMs I replaced in a 64C once). > > Any ideas how to proceed from here? I have a working CBM 8032 from where I can borrow chips for testing. > -- > > Best regards, > Ville > > > Message was sent through the cbm-hackers mailing list > > firstname.lastname@example.org SDF Public Access UNIX System - http://sdf.lonestar.org Message was sent through the cbm-hackers mailing listReceived on 2013-11-02 06:00:08
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