Mod to 3200S to give output to DMM.

[jvthorsley]

After some years of fixing various problems on my ProTrack + Scanner but still giving intermittent  inconsistent results usually with urgent jobs decided it was time to upgrade.
I was lucky to find the the U.K. distributor over here, CTS Combined Test Solutions had a demo 3200S available for sale. And at an affordable price.
But still needed to connect the Tracker to my DMM (Agilent 34410A)  using Workstation 4.3.
The photo below shows an example of high resistance shorts developing between pins under the connector housing.
This particular PCB is used on a Combine Harvester. 12 V.D.C. system with lots of available current that can cause a major burn-up when shorts as shown develop. Caused by a mixture of humidity & dust.
These shorts don't always show up when just relying on the 100 K Ohm range on the Tracker.
The 3200S has all the usual stuff as a ProTrack + Scanner but no output from the Scanner to connect to my DMM.
The connections on the back of the 3200S are designed for Huntron Probers.
I removed the top off the 3200S and worked out the necessary mods to achieve what I needed.
First cut the two outer wires going to Ch. A & B BNC connections on the rear panel from on Plug J4 on the logic PCB behind front panel V & A switches. But kept the centre lead on J4 going to COM BNC plug on the rear.
Then took a lead from the red wire on J7 (near to PSU) to BNC plug formally Ch. A connection and now labelled "Output to Tracker / DMM".
Next took lead from red wire on J6 (Behind ESC, up & down switches). This red wire goes through a transient suppressor choke mounted above J6. Then took the red wire to BNC plug formally Ch. B connection and labelled this "Input to Tracker".
And when using the 3200S in "normal" mode linked the two former A & B BNC connections with a short BNC lead as shown on photos here.
For measurements with my DMM removed BNC linking cable on rear and took one lead from DMM to "Output to Tracker / DMM. and other lead to an adaptor board using IDC ribbon cable from front panel IDC plug on the 3200S. Whichever pin is used on the adaptor board determines the connection to reference to for resistance measurements.
This mod enables me to make measurements to the first 64 pins on the front panel IDC connector.
I have mentioned previously on this Forum details of the adaptor to make measurements on my ProTrack +Scanner. The same method applies here.
And after doing this run the Alignment tests with the top back on the 3200S & BNC cable linking the two connections on the rear side.

[Al1234]

Nice, congrats on you new toy.
when you say hi resistance short. what is the resistance you get on that short. I think, I am dealing with a hi resistance short that is why I am asking. but the short I am working on seems to be between the layers, I think, but yet to be confirmed. 

[jvthorsley]

Shorts in the M Ohms range show breakdown of insulation between connector pins under the connector housing.
I have attached a few examples of problems found under connector housings.

[Al1234]

I am having a resistance of about 740 ohms when red lead is on VCC,  black on Vss, and about 525 ohms when leads are swapped on several ICs and across several bypass capacitors. Huntron ProTrack shows it as a shorted diode between this + & - supply rail. I think this is a short, since there is a blown fuse here connected to this rail. but that remains to be proven. I been removing component off the board. it does not seem to be any of the component on the board causing this low resistance between + & - IC supply voltages. when components are removed their input voltage supply pins measures in M ohms.  scanned the board with thermal camera and voltage input, nothing. The board seems to be several layers. with the polar 950, the short indicator tone changes tone when pressing on the board and minimally whopping it, indicating more or less resistance. I wish I had a good board of the same, but they are expensive. any input would be greatly appreciated.

[jvthorsley]

Hi AI1234
So you have a multilayer PCB there with a short.
Excellent piece of equipment the Polar 950.
Although Polar no longer manufacture the Tone Ohm 950, last time I enquired they could still supply the test probes.
Sorry Huntron its better than the one you manufactured.
Have you tried the "Plane stimulus connection" shorts detection method on this PCB.
That is with four plane stimulus leads at the four corners of the PCB?
A company over here telfordelectronics@btinternet.can  supply the operator manual for this piece of equipment that Polar no longer manufacture.