Another Hewlett-Packard Loot in L.A. (Patreon)

There was (and still is) an ongoing auction in Los Angeles from the former Max Sands test instrument rental company. Which has tons of very, very antiquated instruments (how could they still possibly rent them?). I could have bought my entire collection in one fell swoop. Instead I went looking for odd instruments that would help us in restoring Apollo communications equipment (in the 2GHz S-band). And got quite a few more while I was at it ;-). On the table are also three gifts from viewers, some rather major. As usual there were a some great buys, fortunately just one major dud, although more than compensated by very nice unexpected surprises that came along with the large lots. 

A lot of the stuff did not work when I got it, and I wanted to go through the pile quickly. When I don't film, I can clean, test and repair one or sometimes two a day. If I do film, it's more like one a week... So I did not film! Most of the pile is repaired now. One is un-repairable. The few left over are just too involved and too good not to film, so I kept them for later videos.

The "Apollo S-Band" stuff first. Here is a HP 8364A mixer-in-a-box. Very wideband (2GHz-18GHz), super easy to use. Here I feed it with a modulated signal at 2106.4 MHz, which would be the frequency used by the Apollo Command Module.

It gets mixed with the 2360 MHz local oscillator sitting above, and out comes the mixed-down IF signal at 250 MHz on the spectrum analyzer. I could even bring it all the way down to 10 MHz and feed it to a HF ham radio if I wanted to. This instrument worked right off the bat.

But what if you need more pah-wer? You need a microwave amplifier! Like the HP 11975A, another wideband amp, 2 to 8GHz. It has auto-leveling, so it appears flat as a pancake on the VNA trace. Got three for a fraction of the price of one. Two worked right off the bat, the third one needed a day of work (weird problem in the auto-level circuitry). I don't need 3, but I just can't stand to toss one of these beauties.

Also, by complete accident, I got some random microwave antennas mixed in the instrument lots. I got 4! By sheer luck, 3 of them cover the Apollo S-Band. My favorite is the cone head / clown hat antenna below, of which I got 2. 

I looked them up, and they are apparently highly sought after and very valuable. Like in above $500 each. That would pay for the whole auction and then some! These are spiral cone log antennas, also very wide band: 1 to 10 GHz. For circular polarization I presume, which is what Apollo would have used.

The dud of the bunch was the HP 8981A vector modulation analyzer, which is the main instrument that drew me to the auction. Looked good from the outside, powered  up, but nothing came on the screen and buttons were unresponsive. That would have been a tough one to repair no matter what (schematics were not published), but a quick look inside revealed that it had been raided for parts. 

The top board of the HP 1345 vector display is missing. And it's a modified 1345, so you can't even borrow a board from another lesser instrument.

And 3 of the boards are missing at the back, a RAM board and two AUX boards. 

Nothing I can do to save this, except sell or give away the parts to others that have more complete instruments in need of a new board. I didn't pay much for it, but it always makes me sad to see butchered instruments.

As you can see, I also got a ton of power supplies: we could always use more when the full team is in the lab. I was after the HP 6226s and 6220s. Small, accurate, powerful, go up to 50V. A subscriber gave me my first one (it's the one with the slightly yellowed dial on top of the 8981A in the family photo), and I just loved it, using it all the time. Much easier to set and wider voltage than the digital ones. Don't you love the predictable 10 turn pots instead of the turn-for-ever/connected-to-nothing digital ones! So I got a large lot that had three more, and then some. None of them working at first, but all repaired now.

I even got a surprise non-HP interloper. Look at the spectacular double-double dials! Looks like it has 4 digits of resolution. It's a Power Designs Model 2005, from the 1960s. It is entirely made of 1960s (germanium?) transistors, and the sensitive parts are in a temperature stabilized oven. Dave at the EEVblog has a teardown of one ( https://youtu.be/xc2HKX6XwiA ). Mine also gave far-off voltages, also on the high side, at first. But it only needed lots of DeOxit on the rotary dials and a recalibration, and voila. 4.321V you ask, 4.321V you get. OK, I cheated a bit on the photo, I gave it a 450 μV correction on the vernier and waited that the voltmeter digits passed through 00 (the two last digits fluctuate a little bit). But still, I was amazed!

And from the same lot, here is the equivalent HP 6114A I was after, doing the same trick:

The HP is about 50 times more stable though, only the very last digit moves, and then just a little bit. I still had to help it with 1 graduation of fine adjustment for the photo, but I have not re-calibrated it yet. It worked like this right off the bat.

I also got a whole pile of what I thought were high voltage supplies. They actually are high voltage leakage testers used for certification, or "hipots" as they are called. They only output some voltage when you press the test button.  Here is 2 kV for you, works all the way to 4 kV. Should be usable as a HV power supply by replacing the test button with an on/off switch and moving the tripping point all the way to the max 10 mA. Maybe. I don't know how well regulated they are.

I also got a series of rare collectible Tektronix plug-ins for my Tek 7854 scope, also famously expensive at the time. I had been looking for these for a while, but even now they are always far too expensive. You can see them in the center of the family photo: the 2.5 GHz and the 18 GHz Spectrum Analyzer plug in, the dual channel 1GHz sampler, and the logic analyzer plug-in in particular. None of them anywhere close to what the equivalent HP instrument could do, but the engineering to shrink them to this ridiculously small form factor is mind-blowing. If just one of these worked, it would be worth many times what I paid for the whole lot. And two seemed to work, at least a little bit!

Here is the Logic Analyzer, displaying its glorious screen of 1's and 0's. Don't know if it really works as the probes are still on their way (courtesy of eBay), but this is very encouraging. 

And here is the 1.8 GHz Spectrum Analyzer displaying a signal peak about where it should be. Not all the bandwidth filters seem to select as they should, this should be a great repair.

The 18 GHz SA and the 1GHz sampler did not work at all. They will be very interesting and challenging repairs, it's crammed with boards and very complicated in there.

Back to the HP stuff. One of my favorites of the bunch is the HP 7132A dual pen chart recorder. I had wanted one for a long time. But these are very fragile and very hard to get in good condition, and likely to get ruined in an eBay shipping. It's a very "open" design. The bits that stick out and get banged, and rust and dust gets the better of the inside. But not this one. Look, it wiggles! It was repaired in a single day, with just 5 rather minor mechanical problems. It still had paper in it and a pen that almost works!

Last but not least, the donations. From subscriber Jim Gallagher, this superb 6 digit Nixie digital voltmeter from the 1960s. It powers up, lights all of its Nixies, then goes straight to overload. It measures 1200V with nothing hooked up! But this is a fascinating instrument, using Voltage to Frequency conversion, and with zero ICs inside. All the logic is with discrete transistors. Crammed with boards everywhere. This is going to be an epic repair.

And from viewer Kees Van der Pool, who was the manufacturer of the critical part of HP optical spectrum analyzers, this monster HP 608D VHF generator. All vacuum tubes of course. This is one of the most famous early HP instruments, and spawned the whole line of superlative HP RF instruments. Also going to be an epic restoration, outside of my transistorized comfort zone.

Phew. That was quite a bit, and I skipped a lot. With that huge backlog out of the way, I can hopefully get to the mechanical Soyuz clock next.

Cheers!

Marc