[sebhc] H89 diskette drive

[Carroll Waddell]

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.
Carroll
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
>
>
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