HP-45 clock circuit repiar
Message #1 Posted by albert wambecq on 13 May 2005, 4:24 p.m.
My almost 30 year old HP45 failed to function some weeks ago. (It is one of the first HP45's, so this one has still some HP35 circuitry and chips in it)
I found a lot of usefull information on this website. Thanks for this.
Now, after connecting scope to various signals,
I suspect the 855 MOS clock driver on the logic PCB is faulty. (Phi-1 in and Phi-2 seem to be correct in amplitude and timing, and Phi-2 out seems to be correct in amplitude between Vss and Vgg, and timing. However, Phi-1 out seems only to pick-up some spurious leftovers from phi-2 out, so neither its amplitude, nor its timing is correct)
Anyone has ideas on how to either replace the 855 chip, or generate the Phi1-out signal in another way?
Thanks in advance for your efforts.
Kind regards.
A. Wambecq
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