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
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