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View Full Version : I need some repair help with a Heathkit H89A



Gribnitz
March 6th, 2015, 06:46 PM
I picked up a Heathkit H89A for $10. The store had it marked "AS IS do not turn on - smokes", so it obviously is going to have issues. I can't figure out how to crack this thing open to even take a look. Does anyone have a PDF of the schematics, or the assembly instructions? I think these used CP/M correct?

krebizfan
March 6th, 2015, 07:09 PM
Opening the case is easy. Tabs on each side of the case need to be pushed back and the top will rotate up. Usual disclaimers since I don't have one here and it has been years since I last opened one.

Manuals you could try http://sebhc.lesbird.com/documentation.html#HZ-888990

OS: There was a choice between a CP/M variation and Heathkit's own HDOS.

smp
March 7th, 2015, 11:30 AM
You really want to link up with the SEBHC Google Group:

https://groups.google.com/forum/#!forum/sebhc

The folks there are very active, and H89s are a primary interest.

Good luck!

smp

mgarlanger
March 7th, 2015, 03:10 PM
Opening, is fairly simple. On my site, I have diagram showing how to open: http://heathkit.garlanger.com/howto/

I second the recommendation for sebhc. I've been on there forever and people are really good with providing help.

Gribnitz
March 10th, 2015, 04:37 PM
Thanks for the pointers! I did manage to get it open and found that 2 of the small 2.2uf capacitors had blown. I ordered some to replace them and hope all goes well. I need to locate some software for it as well. This is my only CP/M machine (with the exception of a QX-10 I need to sell).

SGTSQUID
March 14th, 2015, 07:58 PM
I have an H-89 that I will get to working on soon. The floppy drive clicks but doesn't spin, so I thing something is just frozen in there. I have a bunch of software so I can get you some copies if you're interested.

MicrocomputerSolutions
April 12th, 2015, 11:08 PM
I have an H-89 that I will get to working on soon. The floppy drive clicks but doesn't spin, so I thing something is just frozen in there. I have a bunch of software so I can get you some copies if you're interested.



You want to check the voltage outputs from the power supply before you blow any more caps on the terminal or computer boards. The early H-89s power supplies didn't include heatsinks on the voltage regulators, or the larger diodes on the power supply boards that the later models got and have a tendency to blow diodes.

I also recommend replacing the Tandon or Wang full height 5.25" drives with two half-height Panasonic 5.25" drives. The Panasonic drives are much more reliable than the Tandon or Wang drives. If you can get one, or have one of the external drive enclosures you will eliminate a lot of heat from the case. Get the highest output fan that will fit on the fan bracket on the cover that fits.

If you have/get soft sector controller you can get a lot more capacity out of the mini-floppy drives. I prefer the CDR controller over the Heath or Magnolia controllers.

I worked in the LA Heathkit store back in the early 1980s (worked as the Assistant Manager and ran the Repair Department among my other duties), and still have the CDR controller software and program to generate CDR compatible versions of CPM for use with the CDR controller.