[vcf-midatlantic] H89 for museum; gotek?

[Herb Johnson]

Preserving continuity of thread-subject; item below was posted in the 
May Repair thread. - Herb

> [vcf-midatlantic] May Repair workshop
> jsalzman at gmail.com jsalzman at gmail.com
> Tue May 18 12:35:40 UTC 2021
>  
> 
> I did more work with my own recently acquired H89 that I brought. Herb was
> eminently helpful in figuring out what I had available, and was able to get
> it booted with the disks that came with the acquisition. I spent most of
> the weekend working out some of its little issues after it had been sitting
> for over 30 years.
> 
> [other matters deleted]
> 
> One of the last things I did before leaving the event was to take a closer
> look at the Museum's H-89 that Herb was working on. I pulled the drive
> controller card and found a great amount of green rot on the main
> controller IC's socket and pins. There was no noticeable damage to the
> board.  I replaced the socket and cleaned up the pins of the IC. That
> didn't change the behavior of the drive controller, but it was certainly a
> needed fix. The rest of the board is all 74XX TTL logic. The board could be
> refurbished easily if the primary controller chip is still good. There were
> a couple TTL chips that had similar rot on them, but not nearly as bad. It
> was running late for me, so I didn't repair/replace those sockets at that
> time.
> 
> Jeff Salzman

Jeff, thanks for the Sunday follow up on the Museum's H89. If I can work 
on it again, I will contact Jeff Brace accordingly to set a date. I see 
mid-June is a workshop, but I could stop by when the Museum is open.

On Saturday, the H89 was working, booting HDOS, but had some issues. I 
saw some socket and chip corrosion, probably due to some local moisture; 
I took no action, Jeff Salzman did his follow up, thanks for working on 
that floppy controller. I don't believe I saw problems with the floppy 
controller.

The problems I found were: some keyboard keys did not produce the right 
ASCII code (garbage); cause undetermined. There's a 20V DC issue 
(details previously in this thread) which I haven't decided on a fix 
for, it is not "broken" just too high for known reasons.

Also I did not restore the H89 external drive's gummy spindle; I did 
restore the H89 internal drive's spindle, same brand/model of drive. So 
the same fix is needed. If I'm smart, I'll bring a working drive of the 
same brand and model if I have one in my stock: save myself on-site 
time. Or I will rob one from another H89 in VCFed Inventory. (If people 
are curious, I'll identify the drive at some point.)

Plan B, would be to restore another H89 from the VCFed Inventory. A 
backup unit is also a good Plan B for the Museum. I'll inspect the 
inventory of H89's if time permits or parts are needed.

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
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