How to Open the H19 or H89 Case

Both the H19 and H89 uses the same case, so this applies to both of them. (And any of the different configurations such as the Z19, H88, Z89, and Z90). Use a flat-head screwdriver to slide the latches on each side of the  case (near the front) to release the top. For most systems, you will slide the latch forward, slightly push that side up and repeat on the other side. I have ran across some H89s where I needed to slide the latch backward. Typically, the latches are spring-loaded, but I also have some systems where the latch does not have a spring.

This graphic came from a Magnolia Microsystems manual. Click on the picture for a bigger view.

How to Ship an H89

Care must be used to when shipping these 30 year old systems. Over time, the mounts for the CRT can became brittle and with rough handling, the CRT can break loose and cause damage to both the tube and circuit boards inside the H89.

Here is a short document by Chris Elmquist, describing a method of packing the H89 for shipping that has been successful. As always, depending on how rough the box is handled by the shipping company, damage may still occur to the computer. But this should help increase the chance that the system arrives safely.

Patching HDOS to be Y2K Compliant.

HDOS is not Y2K compliant. It has a 6-bit date field that is used as an offset from 1970. So, although the 6-bits could get us to 2033, it validates years to be less than or equal to 99. Luckily, there is a reserved bit in the date format. This allows us to extend the year field to 7 bits and encode all values between 00 to 99. It no longer uses the 1970 offset. Stanley K. Webb created and documented his patch to make HDOS Y2K compliant.

Here is a screen shot from my emulator with the Y2K patch applied:


CP/M compression and archiving basics

CP/M support several types of compression and archiving, the CP/M Compression and Archiving page describes some of these programs.

How to first power a computer after many years in storage

Coming soon...

How to repair an H89

Coming soon...

How to boot a disk

Coming soon..

Other topics coming soon.


Last Modified: Sunday, 25-Feb-2024 22:38:53 PST

Contact Details

Mark Garlanger

Email: heathkit [at] garlanger [dot] com

If you email me, PLEASE check your spam filter for any responses.




This site is dedicated to preserving the history of the original Heathkit computers. They were initially release in 1977 and included the 8-bit H-8 and 16-bit H-11 systems. The H89 was released in 1979.