H89 repairs, CDR items

This Web page last updated JUne 15 2020. copyright Herb Johnson (C) 2020. . IN 2016 and following, I repaired and configured some H- 89's to make use of them. I also have some CDR brand boards for the H-89. I"ve worked on H-89's before and other Heath/Zenith computers: Check my Heath Zenith computer Web page. - Herb

- Herb Johnson

CDR-brand cards, H89's in hand and in progress

In May 2016, I obtained some CDR brand cards for the H-89. Hoping to check the CDR boards out and for use, I went through some of the H89's I have. Some of those H89's needed repairs, and some needed MORE repairs. I've worked on these H-89's since late May 2016. I have two H-89's that are (or were) stable and working, in various configurations. Plus, I have a few H89's or H19's that needed work or provided me with parts. This Web page points to my work on all these H89 systems, as I put them to use and repair their problems along the way. I havent' got to the CDR boards yet, but at least I describe them. - Herb

CDR cards

Details forthcoming, but here's a list of the H-89 supporting CDR items I have.

CDR floppy controllers as recieved May 2016. I have software and manuals for these boards, also ROMs.

CRD Super 89 memory expansionas recieved May 2016.
CDR S-89 top card, top
CDR S-89 top card, back
CDR S-89 under card, top
CDR S-89 under card, back
CDR S-89 cable to Z80
CDR ROM sets for either floppy or memory.

The CDR Super 89, is a RAM disk, a time-of-day clock with battery, and a SCSI controller. The SCSI controller chip is the NCR5380, popular for that purpose in the era. I have CDR software and a manual for this board, the manual has been PDF'ed, text portions OCR'ed.

Other H-89 boards

As I was annoyed by the lack of documentation for less-common H89 boards, I started a Web page in May 2020 of H-89 accessory boards.

complete and rebuilt H-89s

I first worked on some of my H-89's, at this Vintage Computing workshop in June 2009. I later reworked these in 2011, and then again in 2016 with two more H89's as described below.

Hard sectored 40 track


This is a working H89, 2376 terminal board, 2208 CPU board, with a hard-sectored controller, and a 40?-track floppy drive. It has some other upgrades, courtesy of Lee Hart many years ago. I worked on this H89 in 2009 and 2011. This ran OK in June 2016, over many days of intermittant use.

On June 9th 2016 it blew an AC fuse on power-up. What could it be? I looked in the cabinet and saw no obvious damage, smelled no smoke. So I replace the 1.5A fuse and power it with a variac at 30VAC. Look for hot components (something smelled odd), checked DC voltages. I found some hot diodes by inspection. Turns out, one of the diodes for the 65-volt supply shorted and ran hot. Replaced it with a 200V rated diode. That seemed to solve the problem, system came up OK.

Hard & soft sectored 40 track


this is a working H89, 2650 terminal board, 2549 CPU board, with a hard-sectored and a soft-sectored controller, a 3-port serial card, and a 40-track floppy drive. I worked on this in 2009, and again in 2011. But I had to do more repairs in 2016. Follow this Web link for further repair details.

Among other problems I encountered on this system, were a bunch of failing 20V tantalum caps. In the long term, they fail with age or overvoltage by shorting out. That's a serious problem on high-current DC lines. Shorts will cook and open up PC board traces, ignite the tantalum and plastic cap - literally fire. The solution I chose, was modern ceramic 2.2uF 50V capacitors. Follow this Web link for read the beginning of that Web page, for repair details.


However, I did not test the H89 to boot...until Nov 9th 2016. When I wanted to prepare for some soft-sectored copying, I tried to boot up the hard-sectored controller side; and could not do so. After testing some floppy drives and CP/M diskettes on my "development system", and verifying a good drive and disk there, I tried again - and failed with a good drive and a good CP/M boot disk. I replaced the hard-sectored controller - and got a boot! CRC tests on the files were also good. Whew!

Then in mid-Nov 2016, I wanted to use this system with soft-sectored disks. But the H37 soft-sector controller failed! I hadda fix that controller too. I had three available: a TMSI model that was dead; the Zenith model that wouldn't work; and a 3rd from another recently-obtained H89. Fortunately, the third one worked, and with it I fixed the Heath controller. Follow this Web link and read the second half of the Web page, for further details.

a "rebuilt" H-89


In late May 2016, I pulled a third H-89 from my inventory which needed work, so I could use it for the CDR boards, without disturbing the setups on my two active and working H89's. I describe on another Web page, the work I did on rebuilding this system. But I discovered the AC power transformer on this system was too small to run a set of H89 boards - it was sized for an H19 terminal. I discuss the details on that Web page. Rather than replace the transformer, I chose to use the working CPU board from this "rebuilt" system, and also its voltage regulator board & heatsink, to repair a "fourth" H-89 that needed both. With the smaller regulator set obtained from the system below, I will eventually repair this former system into an H19 terminal.

a "fourth" H-89


In early June 2016, I pulled a "fourth" H89 from my inventory, which also needed work. This system has the larger H-89 AC transformer, as discussed above. See the linked Web page for work done. After repairs to the video card, I swapped in the CPU board and a better voltage regulator board-set from the "rebuilt" system. I'll likely use this system, with more AC power and DC regulation power, for the CDR boards.

More Input!

In the meantime, I wanted more programs for the H89's, and some file transfer capability to and from modern computers. It's modern computers which can Internet access archives of disks (as disk images, I'll explain) Besides, only Heath systems can read Heath hard-sectored diskettes; only Heath 89 owners can create disks for me. So first, I had to sort out how to transfer files to the H89 hard-sectored disks. Then I could transfer between H89's or to and from modern computers.

Next, I wanted to use the H89 program archives at SEBHC. But they were all bit-image files of whole HDOS or CP/M distribution disks - 40 track single-sided single-density hard-sectored. While they offer some software to use those disk images - go to the site and see for yourself - I decided I needed some simple disk-image to file programs. I found an example and rewrote it for use, in Aug-Sept 2016. - Herb

How do you create a disk if you have NO disks? Of course - find someone to send you some bootable disks so you can read and format and write other disks, and run programs to process those disk-images. But there's ways to load software into your H89 which can also receive (by serial) image-file data and create disks. I'm working on one means to get started with such loading software. Again refer to the resources referenced above.

- Herb

Copyright © 2017 Herb Johnson

Herb Johnson
New Jersey, USA
to email @ me follow this link