May 13, 1999

Well, having had to say these things many times but not having any pictures--until now--to illustrate them, here are a few things you WILL need to mess around with your newly acquired vacuum tube nightmare (or dream machine--as applicable). So, here is a small collection of decent but serviceable test equipment that I consider essential to enjoying the hobby and getting the most out of your gear.

First up? A Variac--this is a biggie. OK, you get this old equipment that has been who-knows-where for who-knows-how-long, and is in who-knows-what condition, and what do you do? Here's what you DON'T do--plug it into the wall socket and see what happens. Instead, you pay the piper (and the piper costs somewhere around $180 or maybe more) for a new Staco 10-Amp Variac--or equivalent--as the one seen here (my pride and joy). Those of you that like to dredge hamfests for these things--I've looked and Good Luck. What you'll find are hefty mothers that are either three-phase, have no mounting arrangement, no doubt present a major shock hazard, have discontinuous or otherwise damaged and/or dirty windings, no knob, no switching facility, no fusing, and no three-wire line cord. Get the picture? Spend the money--Newark Electornics has them (too much money), but I got this one at Kass Electronics in Phila., PA for a decent price. It's well worth it and I'd do it again.

Next up, the Tube Tester. Here's a venereable TV-7D/U that I got for $145 and promptly had shipped to Dan Nelson in Phoenix, AZ, who for the flat rate of $45 repairs and calibrates them, and sells complete depot-level service manuals, Compactron adapters and tube test data revision sheets. He ought to run for President--I'd vote for him. He installs socket savers if they don't already have them and he even replaces the meter if it needs it--mine did--all for the same $45 flat rate. Dan also sells used tubes that he tests on his, well, you get the picture. This thing has saved me many, many problems. It catches bad tubes when I buy them--even NEW tubes that I've bought that have tested WAY under acceptable. I send them back and get credit and have never had the results of this unit challenged. How are you going to fix tube gear if you don't know what condition the tubes are in, huh? Tell me--I need to know. This unit alone broke the dam of backed-up broken stuff around here and opened up a whole new avenue of (personal) equipment restoration and repair for me. I now use it in tandem with the next little piece of essential test equipment to characterize octal power tubes, and the two together are a powerful combination.

What's this? It's the dual-analog plug-in plate current meter from Alessandro High End Guitar Products in Southampton, PA (215-355-6424), and merely the most useful tool in your vacuum tube equipment rebuilding and restoration and/or modification toolkit. Why doesn't everybody have one of these? I could use two of them, actually, and I may pony up another $99 (shipped) to get a second. (UPDATE--I believe there has been a not-so-insignificant price increase recently.) Apart from its obvious use as an in-line, real-time plate current meter for use with standard octal power tubes--5881's, 6L6GC's, 7591A's. 7027A's, 6550's, KT-88's, etc., I now use it plugged into the TV-7D/U and take current readings of tubes under test and match them up channel-for-channel that way. The deal is, with this piece between your amp and your tubes, you can swap tubes around until you get a good match, both at idle and under load, you can set your bias to any value you want, watching the plate current--not the cathode current--while you do it. And guess what, you're reading ACTUAL plate current, not some voltage across some resistor in the cathode circuit whose exact value you don't know and furthermore, who varies from channel to channel, or even tube to tube depending on the design of the amp--if it even has bias measurement resistors in it to begin with (the AA-100 doesn't)! This is the nuts, folks.

What's next? Oh, a bank of test equipment almost as important as the other stuff, though you MIGHT be able to do without some of it, but not likely. Here are a Tripplet VOM (that can measure up to 5KV dc!), a Heathkit VTVM (vacuum tube voltmeter--Model AC-13?), a B&K 10+ MHz sweep/function generator, and a Tektronix Model 2215 60MHz dual channel oscilloscope. The 33-volt battery in the Tripplet is shot by now, but it's my backup anyway. Not shown is the meter I use the most--a DVM with capacitance capability and a transistor junction test, and which I depend on for almost everything I do. I forgot to get a picture of that one, but you get the idea. With this stuff you can just about align an FM receiver (a multiplex generator would be nice, though), align a shortwave receiver, repair and modify most any tube and solid-state audio gear, and pretty much anything else you can think of (except TV high-voltage--I don't have a super-HV probe). I'm embarrassed to say I'm still trying to remember how to get some functions to work (like sweeping the bandpass of an IF strip), but it's been a long time since I was a paid bench tech. Anyway, when it's time to be sure, this is what you have to use--your ears can tell you something is wrong, but test equipment will verify it and trace it down its location. My problem is that sometimes I'd rather solder than think.

So that's it--the basic tools you need to get around. Next time spend some money on the infrastructure instead of another piece of gear you barely get to enjoy before you sell it and get another. Maybe there was something simple wrong with it--hey, better yet, call me. I'll give you something for it (cheap).

Next up: books you need--and there are a ton.

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