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Agilent 16720A (and 16522A) Pattern Generator Pod Schematics
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DogP:
Hey,

I recently picked up an Agilent 16702B Logic Analyzer, which included the 16720A pattern generator.  Fortunately, it had cables, but unfortunately, no pods.  The direct outputs from the card are MECL compatible, which isn't very useful by itself, but then you connect pods, which translate the MECL to whatever level you need.  There's a separate clock output, which needs its own clock pod as well.

Some pods are fairly cheap on ebay, others quite expensive.  If you need a whole set of them (like me), it can get pretty expensive.  You can grab NOS MECL translator chips for cheap, and custom PCBs are cheap these days, so I plan to build some of my own pods (some custom pods, and maybe a couple clones of simple pods).

Anyway, I picked up an original 10466A pod, which is a 3-State TTL/3.3V Data Pod.  Since I plan to build my own pods, I decided to start by drawing up schematics of the OEM pod.  These pods are readily available on ebay for $20-$30, so given the cost of components + time, it's probably not worth simply cloning these.  But I figured it's nice to have these schematics as reference (or repairs, or just curiosity).

The schematics, and pics of the 10466A board are attached.  I think they're are correct (and they make sense), though I haven't built a clone from these schematics, so there could be errors... trust, but verify I guess.  I also plan to post whatever other pods and 16702B related stuff I make on Github here: https://github.com/pdaderko/16702B .


For completeness, I had also come across a couple good related resources... this thread discussed building custom pods, and I think the conclusion of using a SN65LVDS33 is a solid choice: https://www.eevblog.com/forum/projects/translating-differential-nonstandard-ecl-signal-to-single-ended-3-3v/

This page has internal pictures of a few different pods: http://www.bitsavers.org/test_equipment/hp/logic_analyzer_pattern_generators/16522A_-_16720A_Pattern_Generator_PODs/

Also, the manuals for the 16720A and 16522A describe the pods (termination, output chips used, etc), so it's worth checking those out as well.

Anyway, not sure how popular these pattern generators are, but hopefully this helps someone in the future.

DogP
inaxeon:
Good work man. I've been on the hunt for a pattern generator several times and finding one with a complete set of pods is always what's put me off.

Very interesting.
DogP:
Thanks... yes, the pattern generator cards always seem to be pretty uncommon, and finding then with a set of cables, and especially a set of cables and pods is never easy.  This has been going on for years - when I bought my 16500A ~20 years ago, it was cheaper to buy an entire analyzer with the set of cards that you wanted, than simply buying the card alone.

On the topic of cables... as I noted in the schematics, the cable is 1:1, so the pinout at the header on the 16720A card is the same as at the end of the cable.  Which means if you're missing the cables and don't care about very high speeds or long cable runs, you could make your own pods that plug directly into the card and have TTL or whatever logic level you want directly out the back.  Or, the cables themselves are simply 10 twisted pairs, so you could probably make your own from cheap CAT5 cable, or even make an adapter from the headers on the board to RJ45 connectors and use ready-made Ethernet cables.

DogP
inaxeon:
Would certainly be interested to see them once they're made up...

fisafisa:
Hi
I have just finished assembling 2 very similar pods.
But I think I have spotted an error in your schematic.
The input termination in my understanding is in fact one 100 ohm resistor in parallel.
Not two in series. In series, if I am not mistaken, should be only 2x50 ohm resistors.
From your pictures you can see that.
For a second I thought I was mistaken..

F
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