Benchtop Multimeter Repair: ebay Bargain Hunt

I picked up a broken Agilent U3402A Digital Multimeter on ebay for a good price, taking a gamble that I’d be able to fix it.  I put together a video where I tear the meter down, diagnose the problem, and come up with a working hack to fix it, all in “real time.”  It’s a bit long, but I thought it would be good to share the process in hopes that someone will learn from it.  I was inspired to make this type of candid repair video by Shahriar from The Signal Path Blog.  If you’ve an electrical engineering geek and have never seen his videos, find some time to watch through his videos!

Here is the video:

For the “too long; didn’t watch” crowd, the problem ended up being a damaged winding on the primary side of the power transformer.  I was able to rewire the transformer in a clever way to revive the instrument.  Good thing, because the transformer does not appear to be an available replacement part through Agilent.  The diagram below shows the transformer wiring, and how I rewired it.

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