[sebhc] H89 docs

Barry Watzman Watzman at neo.rr.com
Fri May 20 03:58:08 CDT 2005

Lee, it is the FCC class B that is the stricter standard.  And my
recollection is that there are only two versions, that the Heath and Zenith
"A" products are identical, and both meet class B.  The FCC made a ruling
that all PCs had to meet class B, the tighter standard, regardless of the
intended use or market.

I would not suggest cutting the schematics apart.  The solution is a large
format scanner.  Kinko's has these, but they charge $25 just to scan one
page.  Richard Pestinger had University Library access to one of these and
scanned the Z-100 schematics, perhaps he can do the same for the Z89
schematics if he still has such access.

Barry Watzman

-----Original Message-----
From: sebhc-bounces at sebhc.org [mailto:sebhc-bounces at sebhc.org] On Behalf Of
Lee Hart
Sent: Friday, May 20, 2005 1:46 AM
To: sebhc at sebhc.org
Subject: Re: [sebhc] H89 docs

steve shumaker wrote:
> What constitutes "late model" H89? (I recently acquired what I
> think is a complete set of H89 docs). Model is 89A and the docs
> are dated 1981.

There are basically 3 versions: The original H89 (kit or assembled), the
H89A (kit version), and the Z90A (assembled unit). Within each version,
there were many variations, depending on what options were installed
(which disk controllers, memory size, I/O boards, etc.).

The original H89 (and H19 terminal) are recognizable by having 10-pin
power connectors at the top left corner of the CPU and TLB boards (the
large 11" x 10" boards at the back of the case containing most of the

The H89A (and H19A terminal) are functionally identical, but have added
shielding and filtering to pass FCC class A and B EMI standards. They
can be recognized by having 11-pin power connectors (10 pins with one
pin cut off) at the top left corner of the CPU and TLB boards.

The Heathkit H89A and H19A versions have more shielding than the Zenith
Z19A and Z90A versions, to pass the stricter FCC class A standards. The
most obvious differences are large sheet metal plates bolted to the
backs of the TLB and CPU boards in the Heath versions.

If anyone need them, I have schematic and manuals for all of these. I
would hesitate to have them cut apart for scanning, though they could
probably be copied intact, as they lay flat when opened.
If you would not be forgotten
When your body's dead and rotten
Then write of great deeds worth the reading
Or do the great deeds worth repeating
	-- Ben Franklin, Poor Richard's Almanac
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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