[time-nuts] 5370A vs 5370B

[paul swed]

Bob how long has it been on
I think it needs to be stable like about 30 minutes

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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