[time-nuts] OT: Question on dead HP34401

[paul swed]

Look at the interrupt lines going to the micro. They are always a good clue.
If you see a repeating interrupt at the same rate that may give you
guidance.

On Tue, Dec 18, 2012 at 4:27 AM, Ulrich Bangert <df6jb at ulrich-bangert.de>wrote:

> > You tie the reset through a 1 K r to vcc and you still see
> > the reset signal?
>
> Yes!
>
> > And you do not see the 7 Khz coming from
> > the switching regulator??
>
> No, it is clearly the line that has its source in the LM2925 5V regulator.
> Note however it MAY BE that an active reset behind the lowpass is an
> allowed
> condition even if it does not originate from the LM2925. The 1 K may be
> kind
> of "decoupling" allowing the micro to reset itself AND U501 on its own, say
> watchdog or, without being "shorted" by the LM2925. So the fact that there
> are reset pulses not coming from the LM2925 are not as spectacular as the
> question WHY they are there.
>
> Best regards
> Ulrich Bangert
>
> > -----Ursprungliche Nachricht-----
> > Von: time-nuts-bounces at febo.com
> > [mailto:time-nuts-bounces at febo.com] Im Auftrag von paul swed
> > Gesendet: Montag, 17. Dezember 2012 15:12
> > An: Discussion of precise time and frequency measurement
> > Betreff: Re: [time-nuts] OT: Question on dead HP34401
> >
> >
> > So we are on the same page
> > You tie the reset through a 1 K r to vcc and you still see
> > the reset signal? And you do not see the 7 Khz coming from
> > the switching regulator?? Thanks
> >
> > On Mon, Dec 17, 2012 at 2:57 AM, Ulrich Bangert
> > <df6jb at ulrich-bangert.de>wrote:
> >
> > > Gentlemem,
> > >
> > > pardon for the delayed answer, I had some extreme busy days
> > the last
> > > week.
> > >
> > > > The floating logic is reset by the LM2925 5V regulator
> > reset output.
> > > > There is no connection to this reset line aprt from the
> > Gate array
> > > > reset input and the micro (80196) reset input.
> > >
> > > Yes, U553 on page 9-15 has this reset output which is
> > called XPONRST.
> > > After it has passed the lowpass R503/C504 on page 9-13
> > (upper left) it
> > > enters U500 and U501. I observe this 7 kHz reset signal
> > RIGHT from the
> > > lowpass even if I
> > > lift up the voltage regulator's reset output pin.
> > >
> > > Best regards
> > > Ulrich Bangert
> > >
> > > > -----Ursprungliche Nachricht-----
> > > > Von: time-nuts-bounces at febo.com
> > [mailto:time-nuts-bounces at febo.com]
> > > > Im Auftrag von Bruce Griffiths
> > > > Gesendet: Dienstag, 11. Dezember 2012 22:46
> > > > An: Discussion of precise time and frequency measurement
> > > > Betreff: Re: [time-nuts] OT: Question on dead HP34401
> > > >
> > > >
> > > > It only resets the earth referenced micro (8051) on power up and
> > > > when pulses on the optocoupler output arent present. There is no
> > > > other connection to the reset pin of this micro.
> > > >
> > > > The floating logic is reset by the LM2925 5V regulator
> > reset output.
> > > > There is no connection to this reset line aprt from the
> > Gate array
> > > > reset input and the micro (80196) reset input.
> > > >
> > > > The relay drivers are reset by a 80196 output pin.
> > > >
> > > > The display logic is reset by another 90196 output pin.
> > > >
> > > > Bruce
> > > >
> > > > paul swed wrote:
> > > > > OK but why would it tie to the reset line?
> > > > >
> > > > > On Tue, Dec 11, 2012 at 3:48 PM, Marco IK1ODO
> > > > -2<ik1odo at spin-it.com>
> > > > > wrote:
> > > > >
> > > > >
> > > > >> At 21:40 11/12/2012, you wrote:
> > > > >>
> > > > >>
> > > > >>> Two comments the manuals available on agilent
> > > > >>> What on earth is a crossguard?
> > > > >>>
> > > > >>>
> > > > >> Data exchange between a floating, guarded circuit and a ground
> > > > >> referenced one?
> > > > >>
> > > > >> Marco IK1ODO
> > > > >>
> > > > >>
> > > > >>
> > > > >>
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