Test Equipment

I read a message somewhere from a guy who collected test equipment. I was both envious and frightened; envious that he was doing it because I could easily see myself doing it too, and frightened because I could easily see myself doing it too.

One of the problems with trying to support the radio hobby is acquiring the tools. I could very easily end up with a bunch of things I kinda/sorta need but don't really have to have, like a frequency counter. But where to put it??? I'm already hard-pressed for room as it is.

So I've been trying to make intelligent acquisitions, just picking up things that I must have or couldn't pass up.

Cen-Tech P77772 Digital Multimeter (DMM)

Yes, I do have a few things made after I was born.

This was a gift from my father for the intro-to-electronics class. They had lab equipment but it was nice to be able to do some of the labs on my own at home, and to do almost anything you need a meter. I already had two cheapies, a little analog that says IBM on it (which means IBM whores out its name for anything) and one of those digitals that Harbor Freight sells for around $5. They're good for testing batteries and little things, but neither inspire confidence. It's like taking an introductory photography class with an old Kodak Tourist.

This is a nice one; I remember digitals from the 80s and 90s and they were murderously slow; waiting for them to update was like waiting for a bus—it always seemed to take 30 seconds between updates, and God forbid you had a poor connection because the thing would never settle. This one's much nicer—the display updates much more rapidly. It's got a big display so I can read it even before I got bifocals; and it's got a rocking display so you can set it at a nice angle even when it's lying flat on the bench. It's got a couple of hooks on the rubberized cradle to hold the probes (though it doesn't do anything about the cables). Fluke has nothing to worry about, but it's a nice unit.

I didn't realize this until I was writing it up—this is the bigger brother to the $5 Harbor Freight (also a Cen-Tech) that's rattling around in my car tool box.

Hewlett-Packard 410B and Hewlett-Packard 512A Vacuum-tube voltmeters (VTVM)

I was taking the electronics class and reading on various subjects, and for some reason I decided that the big void in my life was shaped like a VTVM. So I started looking for one of my own. The great part is that there plenty; the bad part was trying to figure out which.

My father has an RCA Senior VoltOhmyst, and I was leaning toward buying one of those, though it seemed odd to have two of the same thing; why not get something else, figuring one might be strong where another is weak? Or something like that.

Then a funny coincidence occurred: I was on a website reading about the virtues of someone's Hewlett-Packard 410B, when this pair of HP meters showed up for sale; I bought them (cost me more in shipping than I paid for the meters) and was happily surprised to find that they worked. So I lucked out. Plus you can get the manuals for free on the BAMA website (I subsquently found a hardcopy for the 512A at a used bookstore), so it worked out great all the way around.

One of the things I find most interesting about them both is the multiple probes. In my vast experience, every meter I'd ever seen had two probes: one black, one red. These have a bundle and I have to tie them up with rubber bands. The 410B's black and red probes have little claws and nuts to pinch the probe needles, so you can remove and replace them if you need to (which works against me here—one of the nuts and needle is missing, and I'll have to figure out a replacement).

Of course, as with most things I buy from thrift shops, there are problems. The 410 has a sneak short, as I found out when I blew the house circuit, the AC meter is unpredictable and it seems like there was some other problem as well. Plus I really don't like having four probes. It would be great if you could plug/unplug them as you need them, but they're hard-wired in. The result is a perpetual tangle. The 512A also has some issues—it's been so long since I've messed with it that I don't recall what's wrong. It's on my list of things to do (but fairly far down...).

B+K Precision 1525 Oscilloscope

My father was an electronics tech at work; at home he dabbled with projects but most didn't require a scope. When I was growing up he had an old Dumont that I thought was great, but it was also very limited. That was given away, and eventually replaced with three or four B+K's a friend gave him. Those slowly disappeared until he was left with this one, which was given to me when I took the intro-to-electronics class. It was "take it and don't bring it back!" It freed up space on his bench for more useful things for what he did, and he could still borrow it back from me if he needed it.

It's a nice scope. By modern standards I'd call it middle-tier. It's analog and everything new is digital. At school we used a Tektronix which was very, very similar but a bit newer, and I don't think it had any additional features that I needed.

Elenco FG-500k Function Generator kit

Another electronics class acquisition—I wanted to be able to do some of the labs at home. Plus I enjoy building kits. Elenco has a few, and this function generator looked both interesting and useful. I was very happy with it; it's fairly easy to build (I was able to do it), the instructions were clear, and ultimately I had something I could use for experiments. I checked its output on the scope and the wave forms (it puts out sine, triangle and square) all looked great; the square is rounded off at the top speed (1 Mhz) but still perfectly food for what I was doing. Also gave me some practice for my marginal soldering skills.

Heath SM-118A Frequency Counter

Purchased mainly so I could calibrate the RCA signal generator. So far it's been a PITA. I got it on eBay so there's a very good chance it doesn't work (it doesn't), so I also got the owner's manual and service docs. It's from the early 70s so it's still from an era when you could fix things. The parts are all off-the-shelf (i.e. everything is standard stuff you can find in an NTE/ECG catalog. Garden-variety transistors, standard 74xxx ICs, etc. Nothing unusual). So we can fix it—right?

Hell no. Worked three days on this thing and never got it right. It appears that I have a variation—earlier or later, I don't know—which doesn't conform to the schematic I bought. Since neither of us are very good with digital electronics (the Old Man is so-so. My ability is nil), circuit tracing hasn't been working out very well. We replaced a bunch of dubiously faulty parts before we got to the point where we determined we could literally replace every component on the board and still not solve the problem. So it sits in limbo.

Hewlett-Packard 5308A Frequency Counter

Purchased because it was cheap ($30) and it was looking like the Heath freak meter above was never going to be rehabilitated.

This one works, though like most things I seem to get it is not quite right. The HP system here is actually two halves married together: the upper half (display) is a 5300A Measuring System, and the lower half is the 5308A freq counter. So after scouring the net, I finally found some documentation on this thing, and the first thing I read is the 5308A only works with the 5300B measuring system.

Oh, great. So that's why it was cheap. Stung by eBay again. But it arrived and I fired it up anyway, hoping whomever owned it was able to use it with the older 5300A top, and it wasn't just slapped together to sell.

It does work. the 5300A has a six-place readout, and the 5300B has eight places. In various modes the left-most digits get truncated on this thing. So the trick is that instead of using the auto-ranging feature, you set the time base manually and you can keep it within the 6-digit range. At least I've been able to do that so far.

In case anyone cares about the specs, it's 75MHz. Two inputs and you can do ratios and comparisons between the two. It's a counter and a timer, so you can do a variety of things with it that I know zip about.

Funny—if it didn't say HP on it, I'd swear it was a mate to my B&K scope. They definitely have the same look and feel.

RCA WR-49A Signal Generator

Another item I bought for convoluted reasons. I wanted to learn how to work on and align old tube radios. You don't need a lot of stuff for that, but you need a few things like a vtvm and a signal generator (and maybe a tube tester). My dad has a signal generator but he's 400 miles away, so I wanted my own. A local friend has a tube-tester than I can borrow (that's another story).

So I began looking around for something I could afford. My dad has a Hickok 288X which he loves; I thought about getting one but it seemed pointless to have two of them in the family, so I thought I'd look for something else (plus the only 288X I found was too pricey for me). There are lots of Heaths and Eicos out there, but I'm always extra leary of kits that other people built, unless the prices were wonderful and they weren't. Eventually I came across this RCA and thought it fit the bill.

Simpson 260 VOM

Kind of like the B&K scope, it was a "take it and don't bring it back" deal, though really I think he was taking pity on me because I had two analog meters and they were both dogs; one was a super cheapy, and the other was the wonky HP 410 above. This doesn't have the full advantages of a Vacuum-tube model, and ammeter feature doesn't work (hence the masking tape note). But it works fine as a DC volt/ohm meter, and for some things that's exactly what you need.

On the other hand, my Old Man still has at least a half-dozen meters of various kinds and quality salted away, so one fewer won't make much of a difference.