Monday, November 27, 2017

Replace an HP 16047A Test Fixture with a BK TL89F1

A year or two ago I picked up an inexpensive HP 4274A LCR meter at the De Anza swapmeet in Cupertino, California.

Unfortunately, it did not have a test fixture into which one could plug a component to test, so I needed to scrounge one up.

Hmmm...could I make my own?

Maybe, but the text fixture must have four male BNC connectors to mate with the four female BNC jacks on the LCR meter.

I could probably cobble something together, but why not first look for an HP adapter?

HP made a number of different 4-BNC adapters, and the one which shipped with an HP 4274A was the HP 16047A.  (For other adapters, please refer to:

HP 16047A Test Fixture:

I happened to find an HP 16047D on eBay -- it is similar to the HP16047A, except its frequency rating is to 40 MHz instead of 13 MHz.

But the HP 16047D only came with one set of component-lead clips.  There are actually 3 different types of clips (as seen in the photo for an HP 16047A, above), and it would be nice to not have to bend leads to fit my sole set of clips.

I could hunt for more clips, but they typically came with test fixtures, and these fixtures, with clips, usually cost in the hundreds of dollars on eBay.

Somehow I happened to stumble across a picture of a BK TL89F1 test fixture, and I was immediately struck by how similar it looked to the HP 16047A.  Given its sub-100 dollar price, it looked like it could be an inexpensive "connector-for-connector" compatible replacement for a 16047A, and it included all 3 styles of component clips.

BK TL89F1 Test Fixture:

How do specifications compare?


(Click on image to enlarge)

(From: Accessories Selection Guide For Impedance Measurements, Agilent Technologies, April, 2005.)


Model TL89F1
Test fixture for convenient testing of axial and radial leaded type components.
  • Frequency: DC to 10MHz
  • DC Bias:+/- 40V peak max (AC+DC)
  • Operating Temperature: 0 to 40 degrees C
  • Terminal Connection: BNC to 4 terminal insertion slots (radial or axial)

Specifications were close enough for me (especially given the fact that the HP 4274A is a 100 KHz instruments), so I ordered one.  Here is the test fixture and its various adapters, as received:

And its size, compared to an HP 16047D fixture:

Doing a quick test to compare HP and BK test fixtures...

1.  A 1000 pF dipped-mica capacitor, tested with my HP 16047D test fixture:

2.  And now, the same capacitor, but tested on my BK TL89F1 test fixture:

Not much difference!

There is one physical difference between the two fixtures:  the HP 16047A has a plastic piece to ensure that the bias switch is forced into its lowest positions -- the BK fixture has no such block.  Unless this feature is important to you, I believe the BK TL89F1 would be a satisfactory (and inexpensive) replacement for an HP 16047A.  (But, of course, do your own research to verify!)

Additional Notes:

For testing SMD components, the BK TL89S1 could probably be used in lieu of an HP 16034E:

Standard Caveat:

As always, I might have made a mistake in my equations, assumptions, drawings, or interpretations.  If you see anything you believe to be in error or if anything is confusing, please feel free to contact me or comment below.

And finally, I should add -- this design and any associated information is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

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