HP 5221B Electronic Counter

It is a snow day here, so let's take a break from projects and look at an old Hewlett-Packard frequency counter. I purchased this 5221B electronic counter last year in San Diego from a military surplus store. It is accurate within its limited resolution, the nixie tubes all work, and overall it is in fine shape.

The display on the counter reading out 3.885 MHz.

Who doesn't love nixie tubes and the smell of vintage HP test gear?

The 5221B sitting on top of a Racal-Dana 1992.

I wonder who put the 5 Megacycles sticker on there. It fit the look of the counter so I left it.

The internal 1 MHz timebase of the counter is well within spec:

less than 1ppm out and I have never trimmed it.

It is hard to do nixie tubes justice in a picture. You just have to see them in

person to appreciate the depth and complexity of each digit in the display.

The form factor of the counter is compact and well executed.

(It is also very hard to photograph.)

I would love to see the "Digital Recorder" that attached to this!

Gold-plated pins on the ICs and point-to-point wiring.

Definitely an instrument from another era.

I'll have to get in there one day and check the Sprague capacitors.

I have had bad luck with those in the past.

One thing that cannot be experienced from these pictures is the unit's smell. As it warms up it fills the room with the scent of test gear from days gone by.

Thanks for reading!

- Dan W.