I should mention one other thing.? To make the inboard power supplies more possible, and to remove heat from the module, TEK put in a general purpose PNP power transistor and a general purpose NPN power transistor in the frame.? They put in one per slot.? The general idea was to use them for the pass transistors for an on-board regulated positive supply, and an on board regulated negative supply.? The regulator controllers were on the board, the pass transistors were on a nice metal frame that got rid of a lot of heat easily.? These need to be tested.? Your average module tester needs to make sure that the AC windings are properly phased and connected, the DC supplies are within spec (they're all bulk supplies with the exception of the TM5000 low voltage supply: regulated).? The last item is to make sure that the pass transistors are isolated from the frame, and are operational.? Plugins needing more 5 volts or so than could be well built may have a switching supply from 11.5 volts.? Other supplies needed may have 3 terminal regulators or not, but a power supply design for any module generally had to do something.? 11.5 volts unregulated with a 3 volt minimum drop across a 7805 drops down to 8.5 volts, and the regulator is good for an amp or so, so about 7.5 watts/amp drawn, and the case could be the heatsink IF the NPN transistor were not used.
Harvey
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On 1/1/2021 8:09 PM, Harvey White wrote: Ok, perhaps I can clear up a bit of this.
Remember that in the 70's to 90's (roughly) there were no (to speak of) FPGA IC's so digital design was lots of 14, 16, 20, and maybe 40 pin chips, depending on the design.? The more (and perhaps most) complicated chips were 8 bit microprocessors, 64K address space, etc.? If you don't know exactly how this maps out, consider that the processor in your smart phone is a genius, and the processors of that time were, if at all, clever chimpanzees (with apologies to Ham and Bonzo).
So we have designs with a lot of chips, lots of discrete parts, and so on.? Tektronix was doing well in oscilloscopes, but had no share (much) in the test equipment market.? You'd need pulse generators, sine wave generators, function generators, meters, power supplies, and others.
So Tektronix looked at the market for test equipment, and likely noticed several things:? 1) a lot of test equipment setups needed a function generator, meters, power supplies and other goodies. 2) they weren't making any of them, 3) these things were expensive and they were fairly large in size.? 4) a small size test setup, rack mount, desk top, or even portable (look up TM515), well, that could be useful., and 5) if they could figure out a way to sell bits 'n' pieces, and allow people to just buy what they needed, well, maybe there's a market there.
Enter the TM500 series.? Very few have microprocessors, having been designed before the widespread use of such (now, if it DOESN'T have one, it's worthy of note).
Most are discrete circuitry, some have ICs, some have some complex digital circuitry (a counter is not absolutely a simple design..... especially period and time measurements).
So what Tek did is to design a standard sized frame (same width as the 7000 series), same height as the 7000 series, but more shallow.? (saved manufacturing costs).? They provided three DC supplies, a + 11, a +35 and a -35.? Once regulated down, each bulk supply could be used for a number of projects.? They also supplied, *per plugin slot*, three AC windings which could be connected and used to make isolated power supplies in each module (and you need this for meters, for instance).? The DC supplies were all pretty much referenced to a common ground.? In addition, the connector (per module) had a LOT of unused pins.? Those pins could connect to individual circuits in the module, and would allow the backplane to be wired in such a way that the front panel connections would be duplicated on the backplane.? This would allow dedicating slots to a particular configuration, and minimizing front panel connections.? An example would be wiring the output of a power supply to a DMM, or? wiring the output of a frequency source to a counter.? All done under the table.
For power supplies, there are 1,2,3,4,5 and 6? slot frames.? The 5 slot frame is in a luggage style sealed enclosure, and was designed to be able to be shipped on an aircraft, so you could take your test equipment with you.? Tektronix also had oscilloscope modules ranging from small, low bandwidth modules, to storage, to 80 Mhz dual channel scope plugins (double width).
Modules evolved in capability as time went on, so you have 3.5 digit DMMS without autoranging, 3.5 digit DMMs with autoranging, simplified lower cost DMMS, and the like.? Pulse generators went from general purpose to 250 Mhz generators to a specialized 70+ volt output generator with variable rise times.? Function generators were sine, square wave, triangle wave, ramp, pulse, etc.... All depended on which one.? Some had built in frequency modulators and could do (to an extent) pulse trains.
There were power supplies, single, dual, and triple outputs, oscilloscope modules, function generators, pulse generators, meters, frequency counters, digital delays, logic analyzers, and so on (check the TEKWIKI for a good idea, or look in the catalogs).
One problem (at least one) was the development of ATE (hereinafter known as Automatic Test Equipment), in other words, run by a computer.? Tek brought out the TM5000 series, with a slightly different design, but including two very specific extras, a microprocessor controlling everything, and an IEE-488 (GPIB/HPIB) interface.? This allowed the test equipment to make measurements, set up conditions, and such under computer control. They had computer controlled switches and digital input/output modules.
Other modules would include such specialized things as optical (fiber optics) measurements, and the like (don't have any of them!)
So in short:? A modular equipment system consisting of a rack, and plugin modules designed to be used in test equipment setups, very capable of being customized.? Need a rack with 5 DMMS?? go for it.? Rack with 3 counters and 3 signal generators?? Easy. Next setup?? unplug the modules, put them back in stock, get the new modules out, plug them in, and you've reconfigured the whole thing.
WIthin the limits of the equipment and the technology of the time, it was a very good idea.
Harvey
On 1/1/2021 6:52 PM, Lawrance A. Schneider wrote:
TM500 - Ok, it fits a very large set of modules.? Why?? Are there modules that do things that can only be done using a particular module?? Yes, I could read the specs for dozens and dozens of the modules, but that would confuse my unwashed brain even further.? Is this admirable project useful in a way that my R&S RTB2000 and my Tek2465b would find it useful?
I do not want to in any way diminish the project.? I looks to be a true work of art and engineering.? But I have no 'modules' and certainly no power supply for same.? My oldest scope is my pride and joy: 2465BDM.? Why would I accumulate these modules?
I hope no-one hammers me into the ground.? I'm simply TOTALLY IGNORANT of these modules and the power supply for same.
Thank you,??????????? larry
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