Sunday, October 18, 2020

TL-21 Kelvin clip test lead upgrade for DER EE E-5000 LCR meter

There's no shortage of blog posts and videos describing TL-21 probe upgrade for the extremely popular DER EE E-5000 LCR meter. With that said, this post will is somewhat repetitive, but hey, I already took the pictures, so why not share.

For impatient readers, this is what the finished job looks like:

The DER EE E-5000 (manufacturer website) is an inductance (L), capacitance (C), and resistance (R) meter very popular with hobbyists. At a retail price of ~$100 (that's 100 yankee bucks for you EEVblog fans), the device is very affordable for its specifications and performance. Everything would be great if only the device didn't ship with test leads about as long as a chipmunk's tail.

This is the photo of the leads de-soldered from the E-5000's TL-21 attachment, next to a tape measure and a standard Kelvin clip for comparison. The entire thing, part of which is hidden in the probe enclosure, is just over 4 inches:

Thankfully, one can fix that little problem with a new set of test leads and a simple soldering job.

Here's the TL-21 attachment opened up, with original wiring still attached:

I noticed that the negative side didn't have its shielding soldered down:

There was also insulation damage on one of the positive wires:

Here's the board after desoldering all the wires. I took out all of the original solder since I wanted to re-use the through-holes for securing new wires during soldering, and it's always a good practice to avoid mixing old and new solder.

For desoldering, I use the Chem-Wik Desoldering Braid from Chemtronics. This thing sucks!

I used the "Atoplee 1 Set Kelvin Alligator Clips with 4 BNC Test Lead Set for LCR Meter" (Amazon link, no commission) as a replacement for the original wires and clips. These are the most recommended leads for the job since they're cheap (~$20), relatively well-build, and shielded. You need shielding for frequency-sensitive testing with your LCR meter.

The Atoplee leads come with BNC connectors, which you can cut off or desolder them if you'd like to keep a nice set of all-metal connectors with spring strain reliefs:

Here's the board with the positive side soldered down. I added some solder to the shielding strand to keep it from untangling:

A few wires later, the probe finally looks like it's got some usable length:

The new leads successfully passe the open/short calibration, and correctly show zero resistance when shorted:

That's it, thanks for reading!

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