Z80 / Z84C Swap (Doh!)

Jules Richardson jules.richardson99 at gmail.com
Mon Aug 17 15:22:48 CDT 2015

On 08/16/2015 09:48 PM, drlegendre . wrote:
> I placed a disk in Drive A and upon pressing RETURN the display immediately
> stabilized and went into a loop printing "BOOT ERROR" on successive lines,
> eventually scrolling the original boot message off the top of the display.


I dug out that machine's 'twin', and it does the same there (just to verify 
that there's nothing odd about that behavior).

> It did not seem to even attempt seeking the disk - and it behaves the same
> way, whether or not a disk is in Drive A. Tried this routine several times,
> with minor alterations, and always the same - straight to the BOOT ERROR
> scroll and no other activity in the drive.
> Drive LED was on in all cases.

OK... behavior on mine (with no disk present) is that the drives spin, the 
heads step in and out repeatedly, and the LED stays on.

Do you hear the drives spin at all? If not, perhaps check for 12V at the 
PSU. I don't have schematics for the system handy, but it wouldn't surprise 
me if it doesn't use +12V for the drive motors (spindle and head) and maybe 
some of the auxiliary logic (e.g. modem and RS232), but not for the 'core' 
logic - so a lack of 12V might give the symptoms you're seeing.

If it does have +12V, make sure it's getting to the drives - my memory's 
hazy, but I think there's a little power distribution harness/board in 
these systems, so there's some potential there for faults (broken wires, 
dirty connectors etc.)



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