Re: Apple //c Sporadically Crashing into the Monitor

[sean weintz <strap@hanh-ct.org>]

My experience is that random crashes into the system monitor on any apple II is usually caused by an intermittently bad ram chip.

As I recall, the ram on a iic logic board is soldered. Best bet is splurge $50 bucks or so and buy another on ebay.

Stephen Adams wrote:

> Hi folks.
>
> What would cause an Apple //c to sporadically crash into the Monitor? It 
> happens at sporadic times; sometimes waiting until after I've been 
> working a few minutes or crashing immediately after turning the computer 
> on without a disk in the drive. While the Monitor is dumping memory 
> register contents to the screen, the disk drive light will occasionally 
> come on for varying lengths of time.
>
> Sometimes I can clear this garbage with the usual Monitor exit of 
> CTRL-C; other times, only a power recycle will do. If I let the Monitor 
> have at it for long enough, it'll display an entire screen full of 
> alternating lines of inverse "@" signs and half-toned blocks (with the 
> odd inverse/flashing/normal characters scattered randomly about the 
> display).
>
> My //c has a 5.25" drive inbuilt, and when I first bought it, the 
> motherboard was upgraded so that it would work with the UniDisk 3.5" 
> drives. Externally, I have one UniDisk drive and one Laser 5.25" drive, 
> although the computer will crash into the Monitor without those connected.
>
> At one time, I had an Applied Engineering Z-RAM Ultra 3 memory 
> expansion/Z80A co processor board installed, but that has since been 
> removed. This expansion board, when installed, required the CPU and MMU 
> chips to be displaced from the motherboard to itself (as the Z-RAM used 
> those chip sockets on the motherboard as its data pathway). Upon removal 
> of the expansion board, I thought that perhaps I didn't reseat the chips 
> back into their proper motherboard sockets correctly, but reseating them 
> didn't help.
>
> Could either of the CPU or MMU chips be bad? Could the UniDisk upgrade 
> be causing this? Is this a thermal issue (though the problem happens 
> even after the top of the case was removed)? Could this be caused by a 
> failing power brick?
>
> I would appreciate any insights into this problem. I was given 
> approximately 150~200 "Software of the Month" diskettes that I'd like to 
> explore. Perhaps, copyrights willing, I could even turn them into disk 
> images and upload them to a suitable repository. But I can't if my 
> beloved //c is acting up.
>
> Thanks in advance.
>
> Regards,
>
> Steve Adams