[vcf-midatlantic] Xerox Status

[Jeffrey Brace]

Wow! David thanks so much for working on this machine and for giving such a
detailed report. It will be helpful for future reference.

On Thu, Aug 20, 2020 at 10:06 PM David Gesswein via vcf-midatlantic <
vcf-midatlantic at lists.vcfed.org> wrote:

> As previously reported I worked on the Xerox at this workshop.
>
> Short summary: One of the two machines hardware seems ok. Was able to boot
> it. Second machine has a hardware fault. Major issue before machine is
> usable
> is to make a replacement for the missing mouse.
>
> Poor picture of what was a nice looking display booting the Interlisp-D
> that was on the hard drive.
> http://www.pdp8online.com/misc/xerox-screen.jpg
>
> The TL;DR to document what we did. People continuing work should at least
> read the remaining issues at the bottom.
>
> VCF has two Xerox 1108 Dandelion AI machines made in 1985. This model
> was introduced in 1981 if you trust online sources. The hardware is
> identical
> to the 8010 Star Information System except possibly it should have a three
> button mouse instead of a two button mouse. The AI machines shipped with
> Interlisp-D and the Star with office software.  I'm not an expert on the
> somewhat confusing models, operating systems, and names.
>
> The machine I started with last time still had the problem of the
> diagnostic
> screen cycling through the boot options. This is supposed to happen when
> you
> push a button on the control panel. Swapping the control panel did not fix
> it.
>
> I then pulled the cards to disconnect them on the second machine and
> verified
> the power supply was ok. Plugged the cards in and diagnostic display seemed
> to behave. I had tried to make a diagnostic boot floppy from image online
> but I didn't think it was good. The machine also didn't like it.
>
> From the previous workshop the hard drive didn't want to spin up. I pulled
> it
> from the machine to work on. The motor seemed fine but the spindle was very
> stiff. I put some oil on the outer spindle bearing under the pulley and let
> it sit for a while hoping some got in. It started to spin but the belt
> popped
> off as it started to get up in speed. By holding down the belt was able to
> get
> the drive to spin up and it quieted down after a little running. Made
> intermittent noise but nothing horrible. Heads wouldn't move. I opened
> the warranty void stickers to get access to a hole in the cover that lets
> you
> poke the heads to free them. There is a rubber stop for the head that had
> become gummy in these drives (Quantum 2040). With the heads free it did its
> calibrate sequence and I was able to read the drive with my MFM reader
> emulator tool. Drive was serial number c133708 and only had one bad
> sector.
>
> I also repeated this with the second drive. Its pretty quiet but also has
> the bad stop. It required some fiddling with the reader to read which
> I haven't investigated why. Drive was serial number 102842 and only
> had two bad sectors. This drive from the working machine had the nice
> background picture when I booted the image.
>
> When we first booted the machine it looked like it worked but nothing
> was displayed on the monitor and no evidence that the monitor was alive.
> Ian opened it up and we found the board was off the CRT pins. Nothing
> looked
> damaged. When we tried again we got a dim picture. With time it got
> somewhat
> brighter and some adjusting of pots we got a good looking display. After
> we put it back together one of the diagnostics showed it was a little
> offset
> to the right but don't think it matters.
>
> Due to the bad head stop which is likely to restick the heads Jeff and I
> decided to use an emulator for the drive. This will also allow switching
> which
> operating environment is running if we wish to show the various options.
> Unclear if the bearings will be ok with running or will get worse.
> The rubber bumper is on the down side so shouldn't ooze onto the platters.
> Unknown if it is outgassing anything bad. The stop should be able to be
> replaced but would either require arthroscopic surgery or removing the
> platter cover.
> Some info on my previous successful and not so sucessful working on
> these drives.
> http://www.pdp8online.com/q2040/q2040.shtml
>
> Ian Primus was leading the mouse effort. He tried to make an adapter
> for a Xerox mouse from a later machine. Either it doesn't operate how we
> think or the chip is bad. He made an adapter for a Amiga mouse which the
> Xerox responded to the buttons and the cursor jittered around but couldn't
> move properly. He found further information on the interface and it was
> using
> a special encoding, not quadrature that the Amiga generates. Ian and other
> were discussing how to make a functional mouse. I'll let them fill in the
> plan
> if they desire.
>
> I tried the viewpoint image for the Darkstar emulator that I converted to
> the MFM emulator format. It generated error codes 0002 and 0322 which is
> Ethernet faults. I put on a AUI to 10-base-T transceiver and plugged in
> a crossover cable to my laptop but it still generates the fault. Holding
> down
> the button until 1 is displayed to bypass the diagnostic allowed it to
> boot.
> It got to the login prompt. Without a functional mouse we couldn't get
> further.
>
> Discussing with Jeff we decided that Viewpoint would be the best operating
> system to use for the museum display. I left the emulator configured to
> boot Viewpoint.
>
> This page give information on running Viewpoint. You can also use the
> emulator to practice with it.
>
> https://livingcomputers.org/Blog/Introducing-Darkstar-A-Xerox-Star-Emulator.aspx
>
> I cleaned up the monitor, keyboard, and plastic skins on the computer. Some
> of the skins were damaged so I cleaned the best looking. On putting them
> back
> on in the warehouse I couldn't get them to fit properly. Either it was just
> too dark or they aren't interchangeable. If so you may need to clean the
> other skins. We didn't mark with machine they came from.
>
> I also put on casters. We didn't try to match the missing originals, they
> are what Home Depot had. Jeff Brace picked them up for me.
>
> During this I also checked the power supply under load. All were ok except
> 5.2 was low at the test connector on the front of the machine. It was
> around
> 4.8 volts. It was around 5.1 at the supply. Poking around to try to
> determine
> where the voltage drop was it improved to about 5V at the test connector so
> likely high resistance connection that improved with moving wires. 5.02
> is the lower limit according to the manual. I didn't see a ripple
> specification and didn't check ripple. I though about looking for a tweak
> pot to raise it .1V but decided not to spend the time. Both machines were
> similar for 5.2 volt output including improving with poking at wires.
>
> This is where time was up. Another workshop should get it ready to use.
> Ian will be leading that effort. I will not be able to make the next
> couple.
>
> I was not able to run full diagnostics. Also have not verified if the
> floppy
> drive is functional.
>
> *** Remaining issues I know of. ***
>
> 1) Make suitable mouse.
>
> 2) Emulator needs to be mounted in the machine. Currently its in an
> antistatic
> bag above the power supply. Two options:
>   a) Remove the hard drive and mount it in its place. Their is a #8 coarse
> thread hole which could be used to attach the emulator if a suitable
> bracket is made. I can make one if people like this route. The disadvantage
> is the hard drive will need to be removed from the computer.
>   b) Make longer cables and mount it above the power supply. Longer 50,
> 20 pin, and power cables cables would need to be made and suitable mounting
> method made. Possibly just some plastic shields so it can short to anything
> is sufficient. Longer cables should work but can't be sure until tried.
>
> 3) Check power supply 5.2V on front connector to see if it is still around
> 5V. Page 6-10, 95 in PDF of this manual has the test connector information.
>
> http://www.bitsavers.org/pdf/xerox/8010_dandelion/service/600P84227_8000_Processor_Service_Manual_to_pg_6-73_Nov84.pdf
>
> 4) The foam in the computer is deteriorating. Its currently at the does
> not spring back stage. Does not seem to be crumbling or generating
> corrosive
> gasses. One of these will likely happen with more time so should be
> addressed
> at some point. Most of it is just for sound deadening so can be removed
> with
> the machine being somewhat louder.  I like to replace it on my
> restorations.
> There was a bigger piece on the front skin that looks like they put it in
> for some purpose that we may not want to just remove.
>
> 5) Check if skins I cleaned fit properly.
>
> 6) There are various scuff marks I didn't bring strong enough cleaner to
> remove on the skins. Does not need to be addressed but will make it look
> nicer. I've had good results on plastic with scuffs using soft scrub.
>
> 7) May want to try to understand the Ethernet error though its easy to
> work around.
>
>

-- 
=========================================
Jeff Brace
Vice President & Board Member
Vintage Computer Festival East Show-runner
Vintage Computer Federation is a 501c3 charity
http://www.vcfed.org/
jeffrey at vcfed.org
cell: 732-759-1783