Electronics > Repair
Series defect on agilent 167xx boards?
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fpgaarcade:
Does anybody know the characteristic impedance of the agilent cables? I can attempt to measure it when I'm back at work.

For reference, the samtec 50R cable I'm considering a play with https://suddendocs.samtec.com/notesandwhitepapers/tcf-3650f-xx-txx_datasheet.pdf

Once we know more about the cable used I can ask around some of my China contacts for lossy micro coax - but full custom gets expensive quite quickly.
MarkL:
If this is just a one-off project...

You could salvage the lossy coax from 40-pin probe cables (ribbon, not woven).  The ribbons peel apart easily if you want to get down to individual or smaller groups of coax.

If you want regular coax (not lossy), the newer 90-pin probe cables could be salvaged and also peel apart easily.  I've measured the coax impedance to be 93R (+/- an ohm or two).
fpgaarcade:
Thanks for the impedance info, that's higher than I expected.

I have sourced some cables now for personal use.  I'm concerned if I make an FPGA board available for others, the demand for these rare cables would increase even more.
If we could find a reasonably priced modern solution which worked (nearly) as well it would help.

I've taken this thread off topic, sorry. I'll start a new one when I have more info.
Cheers,
Mike.
fisafisa:
hi.
Was trying to fix a 16720a for a long time.
it came without cables. Was planning to make my own.

When i saw that a jumper could make the card working, I couldn't believe it.
I had been reverse engineering the card recently and spent many hours  producing a kicad schematic and testing the card on a bus extension.
The main issue I was seeing is that no read clock was arriving to the serial ram.

I tried the fix and immediately it was clear that things were different.
some of the failing tests now simply hung, some passed.

I then tested the card functionally and it worked!

Something is still wrong, as the self test does not pass, but functionally I could not find a problem yet.

 Many thanks
MarkL:

--- Quote from: fisafisa on May 09, 2023, 07:34:23 am ---...
I had been reverse engineering the card recently and spent many hours  producing a kicad schematic and testing the card on a bus extension.

--- End quote ---
Can you post your schematics?  There's so little documentation on these cards that every little bit helps.  Thanks!
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