Author Topic: Old HP 1651B Logic Analyzer cable question  (Read 585 times)

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Offline Squiddaddy

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Old HP 1651B Logic Analyzer cable question
« on: November 20, 2020, 06:57:57 pm »
I bought an HP 1651B Logic Analyzer a while back, and have been working on getting it running.
It was missing every accessory, so I began my scavenger hunt. But it was $10, so I wasn't complaining.
I got a working boot disk, and can boot the unit fine. Was able to make spares.
I also got both of the jumper pods.
But I cannot locate the cables to connect the pods to the unit.
These are different than the ones you find on Ebay.
Those are dual connectors, Pod1/2, Pod 3/4, etc.
My unit only uses the single cables, one for Pod 1 and one for Pod 2.
In a pinch, could I use the 40 pin IDE computer cables, or will that introduce too much noise?
Or does anyone have any sources for the correct cables?
Thanks!
 

Offline oPossum

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Re: Old HP 1651B Logic Analyzer cable question
« Reply #1 on: November 21, 2020, 06:29:36 am »
If you make your own cables then you must use the compensation network shown on page 74. The HP/Agilent cables have this in each probe lead. Using ordinary ribbon cable can work but the cable used by HP/Agilent was quite special and works better.

https://www.keysight.com/us/en/assets/7018-06707/data-sheets/5968-4632.pdf


 

Offline Squiddaddy

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Re: Old HP 1651B Logic Analyzer cable question
« Reply #2 on: November 22, 2020, 02:52:54 am »
Thanks for that reply.
I have both of the pods and all the grabbers.
I'm just missing the ribbon cables that connect the pod to the unit.
It looks like a 40 pin ribbon.
 

Offline tautech

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Re: Old HP 1651B Logic Analyzer cable question
« Reply #3 on: November 22, 2020, 02:57:44 am »
An 80 conductor 40 pin IDE cable could be what you're looking for for better noise specs.
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Offline alm

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Re: Old HP 1651B Logic Analyzer cable question
« Reply #4 on: November 22, 2020, 04:04:14 am »
The originals were either twisted pairs (the early woven cable) or tiny coaxial leads. In either case, the cables were lossy (resistive) similar to the wire used for passive oscilloscope probes

I'm not sure if a 80 conductor ATA cable would be much better than a plain 40 conductor cable, since every other pin is a ground anyway. I would expect inferior signal integrity (noise immunity, crosstalk, emitted EMI, ringing) from using standard ribbon cables. Whether it's enough to cause trouble would be for you to decide.
 

Offline james_s

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Re: Old HP 1651B Logic Analyzer cable question
« Reply #5 on: November 22, 2020, 04:07:46 am »
It's unlikely that any damage will occur either way. Try it and see what happens, even if it's less than ideal it will probably work fine at lower frequencies.
 

Offline oPossum

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Re: Old HP 1651B Logic Analyzer cable question
« Reply #6 on: November 22, 2020, 08:45:46 am »
The old HP woven cables have ground and signal side-by-side. The resistance of both is essentially zero ohms.

 

Offline alm

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Re: Old HP 1651B Logic Analyzer cable question
« Reply #7 on: November 22, 2020, 11:33:28 am »
Is the almost zero resistance for the signal leads, or for the ground or power lines near the edge? What cable is that? I and others have measured cables from several generations of HP logic analyzers using those 40-pin pods, and all had resistive signal leads of about 170-180 Ohm. See for example these posts.
 

Offline Squiddaddy

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Re: Old HP 1651B Logic Analyzer cable question
« Reply #8 on: November 22, 2020, 11:04:48 pm »
Thanks for the feedback guys.
I may try the ide cable to test the unit.
But i will keep a lookout for the correct cables.
 


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