[vcf-midatlantic] H89 for museum; gotek?
hjohnson at retrotechnology.info
Sun May 16 17:42:34 UTC 2021
The subject of the Museum's H89 and the May workshop continues. I'm not
discussing the GoTek.
In short summary, it works but there's some problems. It is not ready
for Museum operation. I did not have time, to work on the companion
external floppy drive, but I am aware of certain problems with it. I
counted the H89's in the Warehouse, there are several which I did not
examine closely. I will follow up in due course.
Thanks to Jeff Saltzman, he provided assistance and tools some bootable
diskettes from the H89 he successfully was able to operate. Thanks to
CDL for their tools and workspace. Thanks to the VCFed staff for their
assistance and borrowing the Radio Club's Variac, and conducting me to
the Warehouse to assess the H89's there.
By "works", I mean I could boot a HDOS 40 track hard-sectored diskette
to the HDOS prompt. But
1) two characters on the keyboard, I and K and J, produce odd results.
So it's hard to operate the H89 if you can't "type" I or J or K. The H89
has a CPU/computer board and a seperate terminal board, they are
connected by a serial link. so the problem is more likely on the
2) The drive and controller are single-sided 40 track and hard sectored.
So only HDOS and CP/M disks for the Heath H89 in that format can be
used. The drive initially did not spin disks well because the hub mech
was gummed up. I disassembled, cleaned, relubricated that mech.
3) There's tantalum caps on the CPU board of the system which are
running just at rated voltage (20 volts). From my experience, they are
at risk of shorting and catching fire. They could be replaced with
higher voltage ratings, or possibly the DC voltage can be reduced, or
the H89 can be run at reduced AC voltage (below 120VAC which is
at-the-outlet at InfoAge). These are known issues with known solutions.
(Readers: there's no need to go nuts about diagnosing these problems.
They are known to any H89 owner who does repairs. I'm not stumped. I'm
just sayin', these are the results of a day's work. )
The H89 as displayed, has a companion disk drive in cabinet. The drive
in it matches the drive described in the H89. It has at least the same
gummy-spindle problem. I did not power it up or work on it Saturday, I
won't be there Sunday.
In the warehouse are about six H89's, condition undetermined. Rumor is,
some were provided as with issues. I did not assess their operating
condition, I just counted them, they are stored where they should be.
I emailed some details to Jeff Brace today, and put paper notes on the
units for the Museum staff. I'll publish details on my Web site in due
course. I may be able to work further on these items, to be determined.
Regards, Herb Johnson
Herbert R. Johnson, New Jersey in the USA
http://www.retrotechnology.com OR .net
preserve, recover, restore 1970's computing
email: hjohnson AT retrotechnology DOT com
or try later herbjohnson AT comcast DOT net
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