[time-nuts] 5370A vs 5370B

[Demian Martin]

Being naïve I didn't know the HP custom chip would be difficult to
substitute. Since it was blown and not available I went searching and found
a Maxim chip (MAX9691 I think) that would work on paper. It is surface mount
and I managed to find a header that fit the HP socket and some careful
wiring from the legs of the chip to the pins on the header got it up and
running. I'm not sure my eyes are still up to this task. It seems it would
be a simple task to create the header with chip. I don't know if the 5370B
would be as easy to substitute.
              -Demian






Date: Wed, 10 Mar 2010 00:03:04 +0000
From: Mark Sims <holrum at hotmail.com>
Subject: [time-nuts] 5370A vs 5370B
To: <time-nuts at febo.com>
Message-ID: <BLU125-W25460FAFB6BA00B5258F2CE330 at phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"


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.

----------------------------------------------------------------------------
-----------------------------------

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).