Taking a break from scopes for a change, I decided to examine a piece I picked up a while back.  Behold the Model 1519 Pulse Counter, by Transistor Specialties.

I really can’t find much of anything useful about this product or company, though it looks like they produced a handful of counters during their seemingly brief life.

A side note: A quick search yielded this gem of a site – americanradiohistory.com which has scans of a number of old electronics magazines.  A trove of geeky goodness, I’ve just downloaded a heap of old ‘Electronics World’ issues from the 60’s for my upcoming 9 hour flight.

Underneath the hood reveals what you’d expect from an counting instrument of this era.

Two beautiful hand-wired looms connect the tube sockets to to the cards, one for each channel.

On the rear are some connections to allow each channel to be started, stopped, or reset remotely, as well as two honking 40 pin Cannon connectors I’ve never seen before.  I’m assuming they convey the current count somehow.  Maybe BCD?

There are 16 identically sized cards.  the first two are identical, the third one is unique, and the remaining 14 are identical pairs – I’m guessing a dual counter & dual driver for each of the 7 digits. Here’s one of the counter(?) cards removed.  This thing is 100% discrete logic; nothing but resistors, caps, diodes & transistors to be found in here.

Note the card connectors, they meet with identical conductors on the ‘backplane’ connectors, which are rotated 90°.  They are similar in appearance, size & operation as the center contact on 125Ω GR-874 connectors.

Update 6/9:  Kurt pointed out that these are the same connectors found on the cards of the 6R1, the digital readout plug-in for the Tektronix 567.  Do check out that 6R1 page, it’s exquisitely documented.

This is a closeup of one of the two input cards, notice the thermally bonded transistors.

These are all single-sided boards, with hand drawn layouts, and somewhat ham-fisted soldering.

This line filter appears to have been added much later.  Because the line cord had been cut, I tacked on an edison tail I had lying around.
Needless Disclaimer: this is temporary wiring for testing purposes.  Do not lick.

Lets fire ‘er up on a variac.  Around 60v, it starts to come to life. 

At full line voltage, it’s stable.

Hitting the reset button zeros out the displays.

I couldn’t get this to trigger on any signal, sine or pulse, from the dozens of hertz to hundreds of kilohertz.  I started metering around on the input board, and there was gobs of 60 cycle that the incoming signal was getting lost in, so I started checking the caps with my trusty Heath IT-28 (which is really deserved of it’s own post).

The big-ass 10,000 uf cap on the low voltage supply proved to be faulty.  Though it passed a leakage test, it exhibited a very low power factor (which equates to a high equivalent series resistance).

A smaller replacement was en route when I just so happed to spy a beautiful 15,000 uf cap of the same form factor at the HOSARC ham fest.  $8?  sure.

I’m still getting some 60 cycle when I poke around, but it’s now where near as bad as it was. Still no worky, the signal seems to die somewhere in the input card. I haven’t decided how much I care about getting that part of it working; I’m more interested in figuring out how to get it to display a number, and if there was a way I could do that without having to send the requisite number of pulses, that’d be swell.

installing and removing the input cards while running causes the numbers to increase, so presumably something is counting.  I still haven’t figured out what that shorter card in the middle does, but removing an inserting that has similar effects.

I’m assuming that each card pair is a decade counter and display driver respectively.  I might suck it up and try to draw out a pair.  I have some readings from the backplane, but I think I’ll pick up with that on the next post.

One more thing: as I was reading Kurt’s post on the 6R1, I realized that the circuit is probably very similar to the counter cads in the 6R1.