*IF* the pods are the same as the basic 166x, 16500x, 16600x, etc then you can look for the following:
the input impedance of the logic analyzer is 10K.? In the pods is a resistor network of 7pf in parallel with 90.9K.? This network is available from HP to be put into a board.? This network should be in the squid adaptor, and this network should be in the pod adaptor (20 pin to LA)
The cables are, if woven, made from nichrome wire having a series resistance of 200 ohms, probably a reason why a straight wire cable from the LA (40 pins) to the adaptors (40 to 20,? etc) may not work as well.
That resistor network forms a 10:1 divider with frequency compensation.
Some of the LA modules have stimulus/digital pattern generators. Those can be TTL, or ECL.? It is possible that what you saw was an output driver if it were differential.? The 16500 modules were 16520, 16521, and 16522.
The intended connection scheme was a squid adaptor to dip clips; use a pod adaptor to a 20 pin socket installed on the board (I do....), or a direct connection with the compensation network on the board (I don't).? There are more expensive connection schemes involving mictor high density connectos.? Those I have decided are too expensive.
Harvey
toggle quoted message
Show quoted text
On 4/16/2023 5:00 PM, Dave_G0WBX via groups.io wrote:
The last time I looked inside a digital pod, (for a different make of logic analyzer, it was mechanically damaged...)
There were some ceramic hybrid electronics.? Not 100% sure, but High Speed, High Z input to balanced output drivers I think, for the twisted pair (per bit) cable to the instrument.? (So the loading on the digital system that you are investigating is minimal.)
I don't know the 54622D, but I'd expect a service (or even the user) manual to have some clues to the exact nature of the logic pod..
Regards.
Dave G8KBV.
