[vcf-midatlantic] Last workshop report

Jeffrey Brace jeffrey at vcfed.org
Sun Feb 9 22:47:27 EST 2020


Thanks for your detailed report. I appreciate all the work that you are
doing for VCF!

On Fri, Feb 7, 2020 at 10:20 PM David Gesswein via vcf-midatlantic <
vcf-midatlantic at lists.vcfed.org> wrote:

>    Executive summary: I checked out the two 3B1's in the museum. One had
> hardware mods to allow more and larger disks and is functional though the
> drive doesn't want to reliably spin up. The second has a motherboard fault.
> I also updated the image on the 3B1 in the Museum and added a USB cable
> hidden behind the center expansion board cover to allow easier updates to
> the
> disk image.  Due to the rain and the filler work running long the Xerox
> 8010
> didn't get that much work done. It appears to have a hardware fault though
> was running some. Fault may just be with the control panel. The hard drive
> wouldn't spin properly, likely loose belt. The second Xerox was not
> investigated at all.
>    The plan was to mostly work on the Xerox 8010 Star/Dandelion but we
> decided to not try to move it in the heavy rains Saturday so I did more
> 3B1 work. I checked out the two 3B1's in the warehouse and removed the
> batteries from both.
>    The first one with sticker NCR SN 02233914 on the side was interesting.
> The motherboard had been modifed to the P5.1 motherboard configuration.
> This change was under development when AT&T killed the UNIX PC line. The
> last software supported it but the updated motherboard was not shipped.
> P5.1 increases the number of heads supported from 8 to 16.
>    The hard disk controller chip was also changed to the WD2010 which
> allows
> the number of cylinders to be increased from 1024. The chip supports 2048
> but
> the operating system limit is 1400.
>    It also had the modification to support a second hard drive. You can
> see
> the grill for one of the fans had been cut down to allow the cables for
> the
> second drive to exit the case for an external drive at some point. The fan
> was reinstalled and no cables are present for the external drive.
> Currently
> it is configured with a single DEC RD54 hard drive. The drive capacity is
> 152 MB vs the standard configuration of 67 MB.
>    I removed the RD54 to backup with my reader. It initially didn't
> want to spin up but with some light hits to spin it around the spindle
> axes it spun up and I was able to read the drive. The MSB for the head
> was put in the sector number byte since the WD2010 only supports 8 heads.
> I hadn't run across a machine with the P5.1 mods so had to fix my 3B1
> decoding
> to match.  The drive label had 42 defects listed. I found 7 sectors with
> read
> errors, the first 5 matching sectors in the defect list.
>    The machine has 2 MB on the motherboard and a 2 MB memory expansion
> board
> so has the maximum amount of memory supported.
>    It also has a floppy tape drive expansion board and cable with it. I
> forgot
> to dig around on the shelf rack to see if the drive was around. May be
> good to
> see if the drive is around so it can be kept together with the computer.
>    This machine had the battery holder installed. I removed the BR2325
> battery.
> You likely can install a BR2330 to get a little longer life. BR2330 is the
> battery I have in the museum 3B1.
>    After I put everything back together the computer was running but the
> hard
> drive wasn't spinning up. Likely the drive is unhappy. I didn't open it
> back
> up to check that I got the power plug fully seated. I also did not test the
> floppy drive. This machine is more tricked out than the one in the museum
> except for not having the DOS expansion board.
>    I haven't looked that much at the disk image. It does have some things
> I haven't seem before, a CAD program and an office suite Smart Software
> System with wordprocessor, database, spreadsheet, and spellchecker.
> It had noticable usage by one user and a couple other accounts.
> A few pictures here http://www.pdp8online.com/3b1/vcf-p5.1/pics.shtml
>    The second 3B1 is labeled 370429065 on the bottom. I was able to read
> the
> drive but it had 50 bad sectors and got worse with further read attempts.
> The drive didn't sound too bad. It's possible that the drive is useable
> with a reformat. The system files were similar to the previous machine and
> it only had one user account with no significant content so I didn't try
> harder to recover the bad sectors.
>    This machine does not complete its power on diagnostics. It has one
> green
> LED lit which indicates that the video ram failed its test. I did not
> try to fix the fault. This machine still had the soldered in battery so I
> cut it out. It was a CR2430.
>    It has a dual serial port expansion board installed without memory
> installed so only has the 2 MB on the motherboard.
>    I opened the museum 3B1 and ran a USB cable from the emulator with the
> end
> tucked above the center expansion slot memory board. It can be accessed
> by removing the center slot cover. It is a USB-C connector. I updated the
> image with some more demo software. Some of the additions are it has BASIC,
> Logo, gcc, Microsoft Word & Multiplan, simple hello world in C, BASIC, and
> Logo, a ~10 line Logo program which draws a tree and the software to use
> the
> DOS coprocessor board. I need to write up a description of how to use the
> stuff installed. I demoed at the workday.
>    Connor was working on a VAX which didn't want to boot. We used my mfm
> board
> to verify that the RD54 drive wasn't going ready. Comparing to the 3B1 RD54
> it sounded like the heads were stuck. He opened the drive and it had a
> deteriorating rubber stop for the heads that was likely preventing them
> from moving. It was a blue rubber ring on the bottom plate of the drive
> and reasonably accessible. He removed as much of it as he could and the
> heads properly went through the startup sequence.
>    I tried to read the drive with my mfm board and it had an excessive
> number
> of read errors to be useful. I did verify it was a VMS disk. It appears to
> have the problem commonly seen where the head stack is out of alignment.
> Some of the heads are so far out of alignment you read the data from the
> next cylinder. Drive may be recoverable with methods like this.
> http://www.pdp8online.com/mfm/head_servo/
>    Connor pulled 2 more RD54's from warehouse machines to try to get a
> good
> image for the emulator in case we can't get one formatted by the VAX. One
> drive
> wouldn't work, I think stuck heads again. The other was readable. It was
> from a PDP-11, possibly a 73. It is RT-11 with KASTLE SYSTEMS building
> monitoring software.
>    Only a few hours were left when I got to the Xerox 8010. I pulled the
> boards
> and power to the hard drive and verified the power supply voltages were
> within specification. I also inspected for anything suspicious. For some
> reason
> the floppy drive power and data cables were disconnected.
>    I released the spindle and head shipping locks on the hard drive and
> verified the spindle would turn.  I hooked up my mfm board and tried to
> read
> the drive. The drive barely spun. I think the belt is slipping. I didn't
> have time to remove the drive from the machine to work on further.
>    We installed the cards and powered on the machine after Connor found the
> power button hiding behind a cover. As previously reported
> the diagnostic display counted from 0 to 10 repeatedly. If I understand the
> documentation, the machine is supposed to cycle through these codes when
> the
> alt boot button is pressed and you release it when the code matches the
> operation you wish to perform. I played with the button but it still
> always
> went though the 0-10 sequence. It is reading the button as always
> depressed.
> The reset button next to it did function.
>    The hard drive power is currently disabled and the shipping locks
> installed.
> The floppy power and data cables were reconnected.
>    The machine is missing its castors. They need to be replaced. It still
> needs cleaning. The one I was working on one of the side panels is broken
> at the bootom. I think the other machine had a good side panel. Their is
> some
> rust but the machine looks in reasonable condition.
>    I did not do any testing on the second machine.

Jeff Brace
Vice President & Board Member, VCF East Showrunner
Vintage Computer Federation
jeffrey at vcfed.org

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