Heath Zenith H-89 boards

This Web page last updated Feb 15 2024. This Web page lists and documents Heath Zenith H-88 H-89 Z-89 accessory boards. I show more H89 stuff on my Heath and H89 linked Web page. This page is preliminary and work in progess. Thanks to Lee Hart for explanations and corrections. Further information is appreciated. To email me, see see my ordering Web page for my email addresses. - Herb Johnson

In May 2020, I was looking around the Web for more information on Heath-Zenith H-89 serial and serial/parallel boards. I didn't find much! And I know where to look. So I got annoyed and started up this little Web page. I'll display various H-89 add-on boards, primarily Heath's, and try to point to or provide docs. Of course, there's many Web pages about H-89's and some have the usual Heath or Zenith manuals on the H89 terminal and CPU boards, power, CRT, etc. I won't add that information here, it's available already.

Boards

Here's the Heath HA-88-3 3-port serial card, 85-2217-1. The photo is of an early model; the HA-88-3A has sets of inductors and capacitors (LC filters) at the serial connectors for RFI filtering. The board has three serial channels using the 8250 UARTs, each with 1488/1489 EIA interface IC's. Interrupts are available. Otherwised documented in later-model H89 manuals.

The Heath Z-89-11 multipurpose I/O card has two serial ports and one parallel port. There's one 8250 UART (same as the 3-port serial board) U604, one 2661 UART/USART (U605, the 26-pin chip, like the Z-100), and one 8255 U606? for the parallel port. Here's a schematic for the Z-89-11 board.Lee Hart added a drawing, of a Centronics parallel cable he built, to run an old-skool printer with Centronics connector, from this Heath board.

This board's serial and parallel chips, have support in the Heath CP/M 2.204 BIOS, to allow for example a parallel (IBM PC style) printer to be used, or a serial printer. However, the DB25 cable Heath supplied to Heath's parallel DB-25 connector, has a *different pinout* than IBM's pinout for their DB-25 "parallel port" connector. One can move around the Heath's cable wires to fix that. Or one can wire a male/female DB25 pair to move signals around. [Notes & schematic provided by Lee Hart; photos by Ted Minchev.]

This is an alternative serial-parallel I/O card. This board was produced by H & H Enterprises, model 703-552-0599 (or that's their phone number?). It has two 8250 serial UARTS (like the Heath 88-3) and one 8255 parallel PIO for use with "Centronics" parallel printers.

Here's the Heath WH-88-16 16K RAM card 85-2731-1. It fills the hole left on the CPU board's 48K of DRAM. Unlike the I/O cards it installs on a memory slot. Documented with the H89 CPU boards.

Here's the Heath cassette card 85-2218-1. On the H88 this was for data storage on audio cassettes.

On the left is the Heath H88-1 85-2219-1 hard-sectored "DISK IO" card. This uses an AMI S2350 USART to format, read and write data onto hard-sectored diskettes. On the right is the Heath 85-2601-1 card, also DISK IO. Same function and much the same chips.

Here's the Heath H47 8-inch drive interface card 85-2442-1. This card interfaced to the Remex brand "smart drives" in the huge H47 box, with its two full-height 8" drives and linear power supply.

Here's the Heath H37 soft-sectored floppy disk controller card 85-2597-1. It was copied by a few small companies. The FD1797 FDC chip does some of the work, the WD1691 and WD2143 chips perform data encoding and decoding. The Heath H-37 manual documents this card.

Photos of two C.D.R. Systems Inc. model FDC-880H" 8"/5.25" soft-sector floppy disk controller. CDR also produced a hard drive controller and memory expansion board. Check this linked Web page for more CDR H89 boards.

For more H89 documentation and stuff

the SEBHC Society of Eight-Bit Heathkit Computerists. H8 and H89 and Z-100 and related Zenith/Heath computers.

"Marcus" HAD some H89 documents among the Z-100 Heath/Zenith documents. Also he has some CDR documents. THis link is dead as of the 2020's. Can anyone remind me, where this archive went to?

The Pestingers Web site has some Heath H89 & Z-100 documents including FDC8800, the CDR brand floppy controller for the H89.