[time-nuts] 5370A vs 5370B

[John Miles]

It should be good to go right away, if working properly.

If it were measuring an independent 10 MHz source at 99.998xxx MHz I would
suspect the thermal fuse in the 10811.. but if it's measuring its own
reference, I'm not immediately sure what would be up with that.  It would be
time to start going through the manual at that point.

-- john, KE5FX

> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
> Behalf Of paul swed
> Sent: Tuesday, March 09, 2010 5:50 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] 5370A vs 5370B
>
>
> I think it has to warm up for about 30 minutes
> Seem to recall interpolators maybe not just seems like that
>
> On Tue, Mar 9, 2010 at 8:37 PM, Bob Camp <lists at rtty.us> wrote:
>
> > Hi
> >
> > Ok, the trigger level pots are bent but functional. The one
> that was stuck
> > works after a bit of readjustment of the knob.
> >
> > All three inputs (ext arm,  and the two channels) blink when I
> put the 10
> > MHz into them. The two with the working pots behave as expected
> as the pot
> > is turned (trigger in the middle, no trigger on both ends).
> >
> > For what ever reason it seems to think that the period of it's 10 MHz
> > standard is 99.5 ns. In frequency mode it thinks the standard
> is at 9.998xxx
> > MHz. Obviously it's a little confused ....
> >
> > Sounds like it's worth working on, unless the 99.5 ns thing
> indicates some
> > sort of massive failure.
> >
> > Bob
> >
> >
> > On Mar 9, 2010, at 7:03 PM, Mark Sims wrote:
> >
> > >
> > > I've had the "pleasure" of fixing way too many 5370A and 5370B front
> > panels.  It's been a while so these musings may be clouded...
> also beware
> > of the two or three different front panel designs.  Also there
> are "hybrid"
> > 5370A's out there with 5370B front ends.
> > >
> > > There are 4 pots on the front panel:  the 470K display update rate,  a
> > 10K or 200 ohm arming level (200 ohm on 5370B and later
> 5370A's),  and two
> > 5K trigger level.  All are linear taper,  all have switches,
> all are small
> > pots with (1/4"? bushings).   Finding pots with proper switches
> ain't easy.
> > >
> > > I have never had to do the trigger level pots.  They have metal shafts
> > and seldom break.  Their switches are what you would expect
> (closed when the
> > pot is turned clockwise).  In the far CCW direction the switch
> is open and
> > selects the 0V trigger level.
> > >
> > > The other two pots are an exceedingly crappy hp design.  They have
> > fragile plastic shafts and really poor quality switches.  The
> switches need
> > to be closed when the switch is counterclockwise. HP's pots have both
> > normally open and normally closed contacts.   Frankly these
> pots are seldom
> > used and you can use a switchless pot and just hardwire those pads.
> > >
> > > The display rate pots is particularly useless.  You can just
> hardwire it
> > to max.
> > >
> > > The biggest bugaboo in buying a 5370 is the state of the HP
> custom input
> > amplifier chips.  They can be damaged by overloading the input.
>   Blow one
> > and you are screwed.  Buy a 5370 with a blown input amp and you
> are screwed.
> >   The 5370A and 5370B used different chips.  The 5345A counter
> is a source
> > of input amp chips.
> > >
> > > It would be VERY nice if some clever person built  drop in replacement
> > "chips" built of modern SMD parts on a DIP header.  Those input
> amp chips
> > are socketed.  They are little more than a comparator.
> > >
> > > Quick check of the 5370A inputs is to set the unit to
> "SEParate" inputs
> > and connect the back panel 10 MHz ref signal to each of the inputs.  The
> > signal level LED should flash.  A steady LED means that input
> is toast (or
> > the input PCB slide switches are full of navel lint and need cleaning).
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