[time-nuts] OT: Question on dead HP34401

Ulrich Bangert df6jb at ulrich-bangert.de
Mon Dec 17 07:57:28 UTC 2012


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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