It's an 8 digit 35 MHz counter with an additional 10 MHz 'B' input that can do frequency, period and count on the 'A' input, as well as interval A-B and ratio A/B. Based on the date codes on various components, it looks to be late 1971 vintage - a glance shows codes ranging between late 1969 and mid-late 1971.
It does power up, and lights the nixies, but that's about as far as things go at the moment. The biggest issue at the start is the opaque display filter - it is crazed to the point of reducing the nixies to indistinct orange glows.
The crazing at first glance was confusing me a bit, as both the front and rear of the window are smooth and shiny. The first task at hand was to get it out for a closer examination. This is proved to be a challenge as it wasn't exactly designed for easy extraction. (Though in GR's defense, I doubt they expected that some nutcase would be trying to fix it 50+ years (
- I remember 1971 - there's no way it's been 50 years since then!!!) later.) As with HP and Fluke stuff of that era, it's very well made.The window appeared to be retained by the thin silkscreened faceplate, which is affixed to the front bulkhead of the counter. The wraparound faceplate can be seen at the bottom of this image, folded back and covering the edge of the raw aluminum bulkhead:
Now for the fun part - getting it apart. There are handles, knobs, switches and BNC jacks holding it on:
Once I got into taking it apart, it proved to be a bit easier than I'd first anticipated - it was just a matter of taking things off in the correct order, as various bits overlap/block access to others, so the sequence was important to some extent. I haven't played much with GR stuff up till now, so it took some cogitation. Turns out that the knobs pull straight off - they are multi-part and consist of a central piece that attaches to the shaft; the knob then fits over it and is retained by a small clip inside that bears on a groove in the center part, which also has flatted sides to align the knob cover. The aluminum center section is on the switch shaft, and the knob resting atop the unit. The retaining clip is at 9:00 in the ID of the knob:
The right side (pictured above) was pretty easy control-wise - once the knob cover was off, the panel would fit over the remaining piece, and the switch was mounted to the bulkhead leaving the front panel cover free.
The left side was a bit more difficult - I hoped the rotary switches would be similar to those on the right, but the power and input coupling toggle switches would need to have their nuts removed, and the BNCs would need to be desoldered and removed as they were front loaded and held from the rear:
Polarity/attenuator & threshold controls were the same as the range switch on the right - once the knob covers were pulled the panel was free from them. The display time was not quite as friendly; it's nutted to the front panel. Knob cover and inner spool had to come off to permit the nut to be removed and the panel be freed.
I made sure to scribe an alignment mark across the shaft face and spool before removing it (once in a while I think of such things in time!)
Now comes the 'order' part - the rack handles have to come off, but their screws are blocked by the side covers that are held in place by screws behind the rack handles and nuts on the back side. Thankfully, GR was thoughtful enough to put holes in the handle faces to permit a screwdriver to pass through and engage the screws. (It would have been simple enough to use a wrench to remove the nuts on the back side, but was far easier to simply hold them still with my fingers and use a screwdriver to remove the screws:
