Cheap auction lot brings nice surprise from the 1960s (Patreon)

You guessed it, I won yet another auction lot. The "reason" I got this was for the Bird Wattmeter (that is, if there ever was any reasoning in this of course). But it turned out the juicy stuff was elsewhere.

Let's start with the Bird Model 43 Thruline Wattmeter. It's a meter to measure the directional RF power traveling through a coax line, usually for measuring transmitted radio power to an antenna. That's a fine example of a product that was designed so correctly in the 1950s that it never got redesigned. Hefty metal case, no plastic in sight, round analog meter. Classic. Indestructible. Mine showed up in very good cosmetic condition once it was relieved from various stickers, scotch tape and sharpie markings that covered most of its surface. But it also came with a little surprise: a scary red tag, artfully hidden in the auction picture of course.

Said "returned unserviced". But there is nothing to service or go bad inside this indestructible wattmeter, it's all passive coax connections. They looked all in good shape, everything was clean and connected as it should inside. All the magic is in the load that you plug in the front and determine the sensitivity and RF band of the instrument (which varies by orders of magnitude depending on the load element), and this one had no load. A used load element is many times the $45 I paid for this, but this was expected. So far, par for the course. 

But like all lots that have red tags to hide, it came dressed up with a whole bunch of generic crap obstructing the view from the correct angles. Most of it was actually not that bad after cleanup. And in there were some unexpected finds. 

First it had 4 Tek scope probes, and to my surprise, two of them were the valuable 500 MHz rated ones. A single used one is worth more than what I paid for the lot, so that's a nice bonus.  The slide-on grabbers were also in the lot, so they were complete. They will rejoin my two Tek 500MHz 7A19 scope plugins that were missing their original, full-bandwidth Tek probes.

Next was a generic looking power supply module. 

It turns out this is a beefy 1.5 kW power supply, 48V 31.2A. You can only get the full 1.5 kW when powering it from 230V AC, but it also accepts 115V AC and will then generate 800W.  By the way you can power it up with just about anything: 400Hz AC if you want, or 300V DC if you feel creative. A quick peek inside showed that is was complete and probably new. 

I hooked it up, plugged it in, and it made the jet engine sound you'd expect from a powerful supply in such a small form factor. And it came right up, 48V on the dot! That could come in handy for powering space or telco equipment. I looked them up on eBay (look for "PFC Mini Power Supply“). There were a few, all over the place from $70 to $500, available in a whole bunch of configs. They look like great affordable industrial supplies when you need some oomph, that's a nice discovery.

But there was still more. This plasticky looking thing from B&K Precision was a bit grungy and covered with metal filings outside, and filled with them inside. Must have been sitting below a mill or something. It looked quite presentable after a good vacuuming and isopropanol cleaning. B&K Precision specializes in mid-range, moderately priced portable instruments. I have their LCR meter, and although not Chinese cheap, it's a solid instrument and a great value for what it is. This B&K 3003 signal generator is $225 on DigiKey, so that would be another nice score if it works at all. Let's give it a try. 

By some miracle there were no batteries inside, so no corrosion. Put the battery in, turn it on, and a beautiful sine wave at approximately the right frequency shows up! How precise you ask? Conveniently, my frequency meter was still on the bench from the HP 9825 clock video. Here is the result:

It won't win you any awards, and there is no way to fine adjust this (come on folks, how hard is it to design a quartz oscillator with an adjustable cap in it?). My lowly 1970's HP clock module got 3 more correct digits than this! Nevertheless, it is within the claimed 0.02% precision spec. I guess the many dials help with setting the very large frequency range (0.1Hz to 10 MHz) with a lot of resolution, but not with outright precision. Definitely a keeper for when you urgently need a random frequency signal at the bench.

And there was one more bonus. While I picked up my lot at the warehouse (this is the great advantage of local auctions - no shipping cost), I looked at the side bench where they take boards apart and sort out components for recycling. In the big messy heap, I spotted a squarish looking assembly which I immediately recognized as a core memory block from the 1960's. 

Was it destined for the trash pile I asked? Yes they said. Can I have it? No they said. I said oh, OK, but went on to explain that this item was really cool, pretty old, magnetic core memory from the 1960's, and that I work at the computer history museum where we make such items work again. The two techs looked at each other with a blank stare. What is it again, they asked? And they just gave it to me :-). Now that was the best find of them all.

I think this is an almost complete 1 KWords 16 bit core stack (so 2 KBytes in modern units) . The magnetic stack itself is complete with all of its bit planes, and it still has one of its address end board with the pulse transformers and the steering diodes at the bottom of the stack. A few diodes were banged up, but nothing that can't be repaired.

Unfortunately, they had already ripped off the top board (one board is for the 32 X addresses, and the other for the 32 Y addresses), so it's missing at the top and there are a whole bunch of wires dangling, which is a bit sad. 

It's branded TMC, which stands for The Measurement Corporation. It may come from this instrument, the CAT 400, built by their subsidiary Mnemotron. CAT stands for "Computer of Average Transients". Actually you probably own a Mnemotron without knowing it! This is the first digital storage scope, so Mnemotron=digital scope=modern o’smell-o-scope. It was of course glacially slow, so it was sold as an averaging measurement "computer", for averaging slow and noisy signals like heart beats, brain waves and other slow and repetitive phenomena (manual here).

Team member Bob Rosenbloom has several of these in his amazing collection . Perhaps we should try to revive one of his!

Saving that memory block made my day. Maybe I'll donate it to Bob. Who says auctions are a waste of time and money. Wait. They are. But it's so much fun.

As always, thanks for your support, much appreciated.

Marc