Hello David,
the 3458A is not offered any more by the usual distributors here in
Germany, like datatec or Meilhouse.
That's due to EU:RoHS directive , i.e. leadfree soldering is required,
and the last exemption for 'measuring and displaying devices' ran out as
of July 2017.
So KS found a way to export that lead containg 3458A directly from the
U.S., but I do not remember the special judicial trick for that... only
that this very same instrument is now called EU3458A.
KS up to now had no chance at all to redesign this instrument to
lead-free, because many special components were either terminated
already, or were custom specific parts, which never had an updated
lead-free equivalent, or were through-hole components with no proper SMD
variant. Just look at that badly designed LTZ1000A reference inside the
34470A, that's nearly a 1:1 copy, but with lower-grade SMD chip
resistors, instead of the original Vishay bmf through-hole ones.
Other examples are the fast comparators EL2018, the A/D hybrid, probably
many of the FETs, and the TaN resistor arrays.
Btw.: In the schematics, sheet 2/5 of the analogue board, current
shunts, there is a strange series arrangement of 'blind' vias.
These solder joints probably serve as thermocouple balancing for the
current resistors, to achieve low thermal voltages.
That's not so easy to be replaced in lead-free technology, either.
The only board agilent did redesign, very probably lead-free, and in a
compatible / plug-in replacement manner, was the µP board.
Up to then, it was easy to buy and insert four 62256 SRAMs and get the
01 option for maybe 30€.
I've done that directly in 1989, for my first 3458A @ university, later
in 2009 for my own hp3458A (2001 vintage), and these RAMs are still
available today, if you have an elder unit.
The new µP board has the memory inside the new ASIC, and that has to be
enabled by a 8 pin IC, maybe a PAL or such.
For the sake of tradition, KS still takes a lot of money for that
option, but you might order this PAL for about 30$, if I remember right,
and get this option for a reasonable price.. but that's not 'official',
and maybe KS meanwhile has shut down this loophole.
Please visit TiNs exceptional website (xdevs.com) for further details
Frank
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