Barrie Gilbert RIP

[ppppenguin]

I've got both the RCA originals and the National LM3080. All genuine NOS.

[Kalee20]

Just picked up this thread. RIP Barrie Gilbert.

The last true analogue semiconductor 'great.' But I didn't know he developed the readout text on analogue Tek 'scopes! Great for when using a camera!

[Craig]

Tek were planning to use a fibre optic readout on a panel next to the screen - like the 576 curve tracer. Gilbert was horrified that what he saw a kludge was going to be adopted. So he built an on-screen readout, skunk works style, out of regular TTL and analogue bits. It was clearly the right solution and Tek committed to custom silicon, which is what is used to generate the on-screen readout.

What is left of the fibre method was on every 7000-series plugin - the little extension on the top of the moulding with four holes in it. Tek had committed to the tooling already, and were not about to change it.

They eventually made use of it with one plugin - the 7A21N direct access plugin. It carries signals directly to the deflection plates through connectors fitted in the four holes. But it is the only plugin that does.

[ppppenguin]

These days when on-screen readout is an inherent part of digital scopes it's hard to imagine the days when you had to read all the information off the knobs and graticule. My main scope is a 2465B which, like all the Tek 2400 series, has on-screen readout. Yes there are artefacts because the time taken for drawing the readout is "stolen" from the main display but it's well worth it. Very occasionally I turn off the readout to get a better view if the artefacts are bad.

Anyone can do an on-screen readout with cheap processing power and programmable logic. It took the genius of Gilbert to even dream to do it with standard parts.

[Mike Watterson]

I refurbished a Tek transistor curve tracer with an unusual arrangement. A column of digital displays beside the CRT so a photo (Polaroid?) would show the settings. Each dot is a fibre. Additional switches and box with lamps and electronics is on each of the controls. It must have been (a) expensive to make, (b) difficult to assemble. Before that I thought the old valve sets with a map and light pipes from lamps driven by tuning were mad (I think an Austrian make and a Baltic copy).

Gilbert was certainly brilliant, but didn't invent the Gilbert cell at all. Early versions used valves. The 7630 was used for similar circuits.

[ppppenguin]

In my original post I stated that Gilbert didn't invent his eponymous cell. However it depends how you define the invention. The basic modulator, as embodied in the 1496, certainly predates Gilbert. In the valve era there were beam switching tubes and other balanced modulators but I don't think anyone used a topology that was equivalent to the 1496. Gilbert has a more solid claim to the linearising of the 4 transistor cell which is probably the one that should bear his name. See the 2nd and 3rd images in https://en.wikipedia.org/wiki/Gilbert_cell