[time-nuts] OT: Question on dead HP34401

paul swed paulswedb at gmail.com
Tue Dec 11 14:19:57 UTC 2012

Yes indeed modern stuff is tough. I believe what you are seeing is a dead
man timer. The system is not booting correctly, times out and resets and
the process keeps going.
Typically a good place to look is at the interrupt lines to see what is
triggering the behavior.
If neither of these are then you are really stuck with tracing down what
device is asserting the reset. If it is an ASIC then you are blind.
The other thing that could cause this to happen is corrupted uproc eproms.
Hard to believe since this is a fairly new device.

On Tue, Dec 11, 2012 at 8:52 AM, Ulrich Bangert <df6jb at ulrich-bangert.de>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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