Is it possible to get a either a part number, or recommended specs for the input protection / TVS diodes D2 & D3?
I was checking out an SMU and damaged my Joulescope. I didn’t think the SMU ranges were at any risk for the Joulescope, but during one check, I did smell magic smoke, and the D2 / D3 area showed evidence of part overheating - it’s possible the voltage went negative while in current mode, though shouldn’t have gone more than 15V negative.
I’d like to try replacing those parts as it seems to be OK otherwise (measurements are still accurate), but I don’t want to run it with damaged or non-functional protection.
Hi @Jeremy
Components D2 and D3 on the JS110 are ST ESDLIN03-1BWY. Components D200 and D1 on the JS220 are ST ESDCAN03-2BWY.
The next components that often get damaged on excessive current & voltage are the shunt resistor selection MOSFETs. A common failure mode is increased gate-source current resulting in measurement offset error. I recommend manually selecting each current range and ensuring that the offset is within spec. Here are the JS110 offset specs:
Use care when replacing these components and try not to disturb the MOSFETs and sense resistors on the other side of the J8 connector. Be sure to remove all solder flux. Small amounts of flux can increase leakage currents.
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Thank you very much!
Agreed on the flux, it has been working with Joulescope that sensitized me to the leakage current from having any residue on boards.
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