iceNINE Tech

- The Tektronix R116 Programmable Pulse Generator -


Here's one that you probably haven't seen before. A perusal of all the usual online Tek haunts led to not one of these very interesting devices being located in captivity. Thus:

The R116 is featured in my 1971 Tek catalog as being a component of their ATE (automated test equipment) system. Pre-GPIB, this system was intended to be used for production testing of semiconductors and other electronics. It goes along with the 568 scope, the 230 Readout Unit, 240/241 Programmers, 250 Aux Program Unit, R1140 Programmable Power Supply, R1340 Data Coupler (for computer interfacing), R293 Programmable Pulse Generator/Power Supply, and some others too.

I saw it at the MIT Swapfest in April of 2007, with a very small price written on it, and was told that it 'didn't power up'. Turned out that the fan was temporarily frozen and was blowing one of (the many) line fuses. A little percussive maintenance, and it spun right up. Now it needs some cal and a little TLC - a knob is missing, some of the larger plastic knobs have seperated from their inserts, and the 0.5V amplitude relay is stuck a lot of the time.

As bought, it is pretty dirty. I want to get it completely working before I clean up the front panel. This picture showcases all the dirt very well - it looks like it was in a decomissioned missile silo or something for the last 30 years. Really though, there is a CDC (Control Data Corporation, which ceased to use that name sometime in the late 80's) property sticker on it, as well as one from a "Computer Peripherals Inc.". The last 'stickered' cal date was in 1980.

(all images can be clicked for larger versions)

It appears in the 1969 catalog (and certainly earlier), is still in the 1971, but is gone by 1975. I don't have any other catalogs to use for reference. There were two major versions of this unit, 'Early' and 'Late'. I have a late one (SN 001425 - no 'B', and circa 1969 based on component date codes), so all my information will be based on that one. BAMA has both manuals (amazing!), but I have lots more to do than compare them for differences. They seem significant, though.

Here's the interior, and an 'action shot':

Now, it's not completely obvious, but if you look closely you can see that the nine PC cards there are socketed into a bus. The connectors used are actually the same ones used on the 5000's, 7000's, 11000's, 26000's, TM500's, and TM5000's (did I miss any?). Tek must have gotten a serious volume buy. So my homebrew TM500 extenders will work for servicing this, once I cut another slot in their boards.

Oh, and there's one of those silvery hour meters, with the bar completely filled, way past the 1000 hour mark. I assume these were supposed to be changed out at every cal or something? It would be silly to have to reverse them and run them backwards for a few weeks in the cal lab...

Spec Sheet Regurgitation

Up to 10Mhz

+/- 400mV to +/- 10V output (50 ohm), with +/- 5V offset

All manner of independantly adjustable period, rep. rate, delay, etc.

Rise- and fall-times independantly adjustable from 10nS to 110uS

<= 3% pulse abberations

Supplemental outputs for several kinds of sync

Inputs for trigger and gating


Here's the 'magic'. In the days before cheap microcontrollers, GPIB, ADCs and DACs on ICs, or other now-common control methods, programming the R116 was a simple proposition. The rear panel has a Centronics connector on it with many lines. Some are digital bits, others analog lines. Each major function has several of each type of pin (usually) allocated to it. The digital bits program the coarse range, while the analog lines fine tune the value. Each front-panel control has a "Remote Program" position, which, whcn selected, allows the rear connector to control that specific function. Any control not so set can sill be otherwise controlled from the front panel.

For example, to program the amplitude output, several digital pins are used to select the base value - 0.2V, 0.5V, or 1.0V. A resistor connected to the analog line sets the 2-10 multiplier. Simple but effective. You'd need to get a DAC unit for your PDP-8, though, if you wanted to vary those resistors!

Also, the manual contains schematics for a very simple 'programmer' designed to exercise the control system for calibration purposes.

Last updated April 18, 2007
Original content copyright © Christian Weagle unless otherwise indicated.