XMAS time for precision project at xDevs.com

Last four xDevs.com ultra-stable reference PCBs for LTZ will find their brains soon.

These are no usual LTZ1000CH’s, I warn you :) Perhaps one can get a hint from a date codes, which is 15 week 1990. These references are well conditioned and aged already, so it will be very interesting to see how these perform compared to my barely aged LTZs, bought from LT in 2014 and 2015.

One interesting thing, these old chips don’t have gold flash on bottom package can, unlike all recent ones. Perhaps packaging was changed, as LTZ1000ACH in HP 3458A A9 PCBA, made in 1993 is with gold-plated bottom already.
Why that’s important? Well, that was one of reasons how we recognized fake LTZs from china before. Old genuine can be without golden plating as well, as it turns out ;)

Pair of National Semi’s LM399 1994 and 1997 to juice it up a bit as well… Aged and ready to go…

And that’s just warming up…

100K precision wire-wounds and Vishay Precision Group VHA518 100K 50ppm 0.2ppm/K foil resistor ? :). Few other values WW as well.

SFERNICE’s 30K 1%, 120R 1%, pair of 40.9600K 0.005% S102C in plastic mold packages.

More wirewounds, 10R, 100R, 300R, 354R, 2K, 1.5K, 20K, pair of 10Ks. They are beautiful, in black shiny epoxy. I wish to have some of that epoxy to encapsulate some of Fluke wirewounds I have….

This is great collection for some tempco testing and comparison experiments I’m working on. But hold on, tempco testing? How can one measure temperature coefficient without good temperature sensor?
Here you have it, YSI 44031 precision thermistor network:

If you click on bigger photo, you will see whole label, which warns you to heatsink leads when soldering. That’s a usual rule for sensitive precision resistors, to avoid hysteresis and shock to element during assembly!

And to couple all this precision gear with your DMMs, make sure to use good pure copper terminals, just like these heavy stuff.
Require bit of cleaning, but that’s no problems. Bigger ones are really heavy-duty, would be great for some decent amps.

I dig out my non-precision weight and compared them together:

There is cheapie brass plated terminal with 35.5 grams as well… Golden spade lug with 14 grams is actually local Taiwan shop one, but it’s real copper with gold plating.

Also I will have one of PCBs for LTZ assembled with this nice beryllium copper gold plated TE AUGAT socket. It clamps pins really tight. Will be a good test to see if quality sockets make any difference on stability or tempco ;)

Have few others as well..

And last , but not least – L&N 12-position rotary switch, just similar to ones used in my recently received 4-decade resistor box

All contacts silver plated, with just 1 mOhm contact resistance and 1pF of capacitance. Will be a great switch for muxing reference outputs.

So thanks for Santa, feeling like a child with big nice candy!

Author: Illya Tsemenko
Published: Dec. 22, 2015, 12:55 a.m.
Modified: Dec. 22, 2015, 1:07 a.m.

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