[sebhc] H89 diskette drive

Carroll Waddell carrollwaddell at sc.rr.com
Mon May 14 12:38:23 CDT 2007

The blown caps were obvious. (Pieces of the cap everywhere). After 
replacing the board was still dead. Using a scope I checked for a clock 
pulse going to the Z80 CPU chip. I was getting a clock input, but no 
outputs from the Z80. Replacing the Z80 got the output lines going. I 
removed all the memory chips, and starting checking 16K at a time, 
starting at the lowest address. Got 16K to work, then removed them, and 
tried the next group of 8 chips. Found a couple of bad ones. That is 
basically all I have done up to this point. Right now, still trying to 
get a diskette to boot.
I give a lot of credit to Lee Hart who told me how to physically locate 
the CPU board so I could use a scope on it. I was going nuts trying to 
scope the board while it was installed (so close) to the CRT high voltage.
Hope this helps.
Happy computing.
ziloo ... wrote:

> */Carroll Waddell <carrollwaddell at sc.rr.com>/* wrote:
>     I got my H89 CPU board repaired and working. ...
>     Carroll,
>     Would you please explain what was wrong with the system and how
>     you fixed it?
>     It would be very educational!
>     ziloo
> ------------------------------------------------------------------------
> Now that's room service! Choose from over 150,000 hotels
> in 45,000 destinations on Yahoo! Travel 
> <http://travel.yahoo.com/hotelsearchpage;_ylc=X3oDMTFtaTIzNXVjBF9TAzk3NDA3NTg5BF9zAzI3MTk0ODEEcG9zAzIEc2VjA21haWx0YWdsaW5lBHNsawNxMS0wNw--> 
> to find your fit. 

Delivered by the SEBHC Mailing List

More information about the Sebhc mailing list