[time-nuts] OT: Question on dead HP34401

[Bruce Griffiths]

Ulrich Bangert wrote:
> Gentlemen,
>
> I own a dead HP34401. On switching it on the display stays dark. It will
> however react on pressing the SHIFT key.
>
> By changing pcbs against a working one the display board has shown to be ok.
> There must be a problem with the main board. Without knowing whats inside
> the ASICs make trapping the problem difficult. One strange thing that I see
> is that there is a 7 kHz repeating reset signal on the reset line that does
> NOT come from the voltage regulator's reset output but must be generated by
> the processor or an ASIC. Anyone having an idea to that?
>
> Best regards and TIA for your answers
>
> Ulrich Bangert
> www.ulrich-bangert.de
> Ortholzer Weg 1
> 27243 Gross Ippener
>
>
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>    
Which reset?
Assuming the circuit is the same as mine (Setember 1991 -October 1991)
The Floating logic reset, the Earth referenced resets: 8051 reset 
(generated by absence of crossguard comms) or the 9914 reset?
The only ASICS are U101(analog switch array), U102(resistor array) and 
U501 (gate array), none of which generate a reset.

Bruce

Bruce