HP Logic analyser module: 16754a repair - Page 1
Forum section: electronics / testgear

author: fisafisa
author_rank: Regular Contributor
timestamp: June 28, 2016, 09:46:00 am
content: https://www.dropbox.com/sh/x3w2zxnsuapjvs5/AAD399H5pZ1OH89jYjWRYWnra?dl=0HiI just bought a defective 16754A. It is a card for the 1670x or 1690x logical analyser system.When it arrived I was shocked to discover the (adjective?) repair job done on the top and the extensive corrosion on the bottom.The memory chips all had salt crystal between pins (need a lens to see them but you can see that they are not shiny as they should)My biggest problem is the fact that some components are obviously missing. (probably same capacitors as the neighbouring ones)and some are probably missing (2 fairly big pads near large chips - probably inductors as the one mounted in symmetric position)To start my repair job, it would be very useful to have some close-ups of same (or similar cards 16753/54/55/56 & 16950)My plan is to clean the oxidation from the chips using a tooth-brush first dry then wetted with distilled water.Then I plan to replace all oxidised passive components (caps and inductors)Then I will test the card again.After that I will remove all the transparent plastic protection sleighs and check for corrosion underneath.Final job is to remove flying leads on the top and to reestablish correct path for supply to FPGA. As soon as I understand why this was done.Any suggestions on how to proceed would be very appreciated!Thanks

author: fisafisa
author_rank: Regular Contributor
timestamp: June 28, 2016, 10:08:59 pm
content: I have added comments to the pictures.The main mistery is the modification to the circuits.It appears that there are at least two cards, modified in the same haphazard way coming from the same source.Other cards, as far as was able to see from the poor images on the web, do not have this mod.The mod takes the supply to the 2 big chips from the lt1580 which in turns takes the power from the inverter circuit (negative boost/buck) which was in fact blown: the diode was shorted thus feeding ac to the circuits instead of 2.5V (my guess from the fact it feeds the DRAM MT46V16M16)..An hipothesis is that the modification overloaded this circuit which eventually blew...If somebody can shed a light on this....

author: fisafisa
author_rank: Regular Contributor
timestamp: June 28, 2016, 10:35:39 pm
content: Maybe some light on the mistery.I have just seen a 16756 with the same mod and the same arrangement of the plastic protection sleighs on the bottom.So two versions of these cards, one with the mod and one without.It means that I need to keep the mod.....

author: gslick
author_rank: Frequent Contributor
timestamp: June 28, 2016, 11:12:17 pm
content: If the 16754A module was fully functional, how would you actually use it? The 90-pin flying lead sets such as the E5382A are crazy expensive, the typical asking price each is higher than the typical asking price for the 16754A module. You could use something like an E5380A 90-pin to Mictor cable, but those aren't cheap either, and then you would need to attach the Mictor connector to the target system somehow.Or would you attach some sort of adapter of your own to the 90-pin module cables?

author: fisafisa
author_rank: Regular Contributor
timestamp: June 29, 2016, 07:11:40 am
content: HiI am interested in the differential capability.So I will develop adapter for a few channels

author: fisafisa
author_rank: Regular Contributor
timestamp: August 13, 2016, 10:04:49 pm
content: The card is repaired. at least 95%Passes all tests but complains on a comparator calibration on a pod...Cleaning... replacing oxidised caps and changing a power diode part of an inverting switching circuit...two use the -5V to supply some +3? railNow the problem is that I have not found yet the pin-out of the 90-pin connectorI know now that there are two i2c channels and and pin dedicated to recognise the pod.It is probably sufficient to provide 20kohm series resistor to have a basic working probe, but somehow I need to make the sw recognise the probe I guess...I need to play a little more to find out.In the mean time if anyone had a pin-out of that 90 pin connector..... that would really help.Ciao

author: TAMHAN
author_rank: Frequent Contributor
timestamp: August 14, 2016, 01:53:52 am
content: fisafisa, sorry - my 16700 did not arrive yet. So I can absolutely not be of help.HOWEVER: I know that there is an "owners guild" of sorts, for old HP stuff. They meet at a Yahoo Group - maybe hitting them up could work!Tam