Zenith MinisPort laptop memory issue?

[Bill Degnan]

Paul,
Worst case you can borrow my copy of that laptop, swap parts until you find
the bad component that way.
Bill

On Tue, Jun 30, 2020 at 8:55 AM Paul Rickards via cctalk <
cctalk at classiccmp.org> wrote:

> Hi All,
>
> I'm restoring a Zenith MinisPort laptop, an 8088 based laptop with a
> monochrome screen and 2" floppy drive.
>
> I have a Twitter thread of the restoration so far with pics:
> https://twitter.com/paulrickards/status/1272280795529519105
>
> I recapped the internal power supply board which seems to be working well
> now.
>
> The next issue appears to be memory. The unit won't store the BIOS settings
> properly, even with new lithium batteries or warm restart. In the BIOS
> menu, setting the clock with a "0" changes to "32". Same with the date, if
> you set the day or month, it adds 32 to it.
>
> The internal memory test reported a memory error at B800:0000 bit 5. This
> seems to coincide with the BIOS "0" turning into 32 on screen.
>
> When it eventually boots from the internal MS-DOS 3.3 ROM, it looks fine
> until the screen starts to scroll. The character case of all text on the
> screen changes from lower to upper case.
>
> Anyone know how to map a bit 5 error to a component on the motherboard?
> Would a memory map help here?
>
> Longshot: anyone have a service manual for the Zenith MinisPort ZL-1 (or
> ZL-2)?
>
> Thanks,
> Paul Rickards
> biosrhythm.com
>