[sebhc] H89 BOOT

Christian R. Fandt cfandt at netsync.net
Tue May 15 21:07:48 CDT 2007

Well Carroll, let's first consider what major things are different betwixt 
the 8 and 89 . . .

Disk drives:  Is the floppy drive in the H89 the same model or otherwise 
interchangeable with the H8? If so, try to swap the known good drive from 
the H8 to the 89 and see what happens. I'm thinking either drive head 
alignment and/or analog calibration out of whack or just a plain old 
hardware failure of the H89 drive.

How about drive cables? I can't recall if my H89 and H8 have the same cable 
connectors at each end, and cannot check without major bulldozing of the 
archive area in this house :-/ , but swap them if they are swapable. If 
you've got a known good spare cable check with that too.

Next, is the RAM size:  Is it the same between the two machines (asking 
this with CP/M's dependency upon RAM size in mind)? It may be okay as one 
of the other fellows here mentioned something about it several days ago and 
you probably already addressed that. Good to do a sanity check anyway.

Voltages? Check +5V and +12V right at the drive on the PC board, while 
drive is commanded to access a floppy disk (+5 & +12 under load), to see if 
the power cable connector pins are okay or not. Loose connections between 
the male/female pins or bad crimp of one or more pins onto their respective 
wires can cause enough of a resistive drop in voltage to affect operation.

Can't swap controller boards between the machines, obviously, so that idea 
is out. Sounds like patient signal tracing if nothing here works.

Good luck and keep at it Carroll. You'll get the problem smoked out 
eventually I'm sure.

Regards,  Chris F.


Upon the date 07:24 PM 5/15/2007, Carroll Waddell said something like:
>If a diskette is bootable (BOTH HDOS AND CP/M) on my H8, should it be 
>bootable on an H89?
>I've tried everything suggested, and everything I can think of, and it 
>still won't boot.
>I had one H89 CPU board with MTR-90 so I tried that in the one I'm working 
>on. Still won't boot.
>Delivered by the SEBHC Mailing List

Christian Fandt,    Electronic/Electrical Historian
Jamestown, NY  USA      cfandt at netsync.net
         Member of Antique Wireless Association
         URL: http://www.antiquewireless.org/ 

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