Problems with IBM 5150 Power

On 27 Jul 2009 at 19:03, Joe Giliberti wrote: I assume you're re-seated all of the socketed chips and probed a bit with a scope or logic probe to see that the processor is at least ticking over--and you've checked your display switch settings. There are inexpensive POST cards that can display any POST error codes, but if you're not even getting a beep, that doesn't sound good. It's not unknown for the old mask-programmed 8Kx8 ROMs to develop bit rot. If you suspect this, you can either use a 2764-type 28-pin EPROM and rig up an adapter to fit the 24-pin socket or pick up some Motorola 68764 EPROMs and program them and use them directly. Amazingly, during the 5150's heyday, they were near unobtainum, but I've seen them offered NOS for something like $6 the each lately. --Chuck