If, like me, you have a Hickok tube tester where on a 12AX7 you have to dial up one cluster of settings to test triode "A" and another to test triode "B"…you know this is a PITA, frankly. If you have a big pile of 12A_7, and I do, often, since I buy surplus gear for these tubes and sometimes get half a dozen..or fifty....what are you supposed to do....test all the triode "A"'s then come back and test all the triode "B"'s? Or flip the knobs back and forth twice per tube? Or, go A > B on tube 1, B > A on tube 2, A > B on tube #3? Recipe for error, IMHO. And lots of wear on the tube tester switches which I would REALLY PREFER not to have to replace.
EVER. So, I decided to build a silly little switchbox with a 9-pin socket and a 3PDT switch so that a 12AX7 can be plugged in and you can rapidly compare/test the two halves without going through the rigamarole of changing 4 or 5 switches. On the end of the cable is a 9-pin "plug" which goes into the tube tester. Nothing fancy. Use good wire, there's volts in there and you're gonna flex them many times.
I had several of these little boxes from a junked radio which turned out to be perfect little enclosures for the remote mini-chassis. Thus I made separate deals for the 12AX7 and Compactrons. I haven't finished the Compactron one yet, but the 12AX7 is working just fine. Of course, one could combine the dual-12AX7 switcher and the Compactron switcher into one box. The switching could get a tad complicated. There's no electronics in the extension box, just a tube socket and a switch.
Likewise, if one wanted to build such a thingy to compare two **individual** 12AX7s, for example, for use in any particular section of a two channel stereo, another DPDT switch and another tube socket, properly connected, could compare tube #1, section A, with tube #2, section A, and tube #1 section B with tube #2 section B with only a few toggle-switch flips. Not bad.
I also built one with a rotary, 3-position switch to test 6C10's which I ran into a pile of. The tester, on its own, has no Compactron socket. Same concept. This way, I am just testing a triple 12AX7 in one bottle...flip, flip, flip.
Junkbox parts, the whole thing, except for the 9-pin plugs, and since I wanted a "socket-saver" or two for the tube tester, I bot 4 of them at the same time. $3 each. The 3PDT switch is actually a 4PDT and I have separated the plate-switch section from the grid and the cathode sections. Left a blank switch-section betwixt the P and G+K. Since this is a little switch, the type that mounts in a 1/4" hole, who knows what the voltage rating actually is? I am *probably* exceeding it.
The “socket saver” thingys are available from a guy on ebay who sells useful tube stuff. I of course wanted to buy the Compactron socket at the same place. His seller name is gobble75 and he can be searched, by seller.
Important with regard to the socket saver thingys: These are VERY TRICKY and VERY DELICATE to take apart and put back together, thus I STRONGLY SUGGEST you buy an extra one for a whopping $3 in case you accidentally destroy it. I did. You'll note, if you look carefully, that I cracked open the base of the socket saver...no problem...I stuck the spare I bought on the bottom and I will wrap the cracked one with electrical tape. So much for trying to achieve a neat job. But it works. HINT: When you take the thing apart, get a junk 9-pin socket, hopefully an old wafer one, and place the ends of the pins into that socket as you solder your wires onto the long pins, to preserve the spacing. If those get out of sync....you'll have trouble re-assembling the "socket saver". NOT ALL socket saver thingys can be taken apart! The ones this guy sells, they can.
(I asked him!)
Hint #2: For the entry wires into the socket-saver, DO NOT try to drill a hole into the side of the overall enclosure. These are made from brittle black plastic and you'll likely split or break the thing. Take the thing apart and grind or file away a "mouse hole" about 3/16" wide and 1/2" long to let the wires in. Obviously, you are going to grind away in the space formed between pin 1 and pin 9.
Hint #3: When soldering to the socket-saver, solder your wires onto the pins of the top socket, as you would normally; do NOT solder to the stiff wires already soldered to said socket. *Any* solder dripped or carried onto those long extension wires will cause you grief when you go to re-assemble the bottom "cup" onto the assembly.
Topic: (Not so) Silly Project (Read 4136 times)