How do I fab a "tube tester?"

[kf6pqt]

My old Heathkit TC-1 (nor that junky Hickock in the garage) has sockets to test the ratty looking 4-400a's I scored off of ebay CHEEEEP, nor will it do my sovietsky gi-7bt's. 

So, aside from the basic checks with a meter, that there are no shorts, and that the filament lights, how does one "test" tubes that one has not yet constructed an amp/tx to run them with?

Thanks and 73,
Jason kf6pqt

[W3SLK]

Jason, see if you can locate some of the old GE Ham notes. I had a fellow ham send me the plans for making a jig just for Xmtr tubes. I believe it came from the ham notes. If I (ever) find them I'll send you the a copy of the plans.

[WA1GFZ]

I scored a box of 4CX3000As once and had the same problem. I was told 2 were almost new and the rest of the pairs were in different age groups. It was pretty easy to spot the newest tubes by the tarnish on the plates. They had been removed from a big vibration test machine.
First I lit them up and measured the primary current into the transformer. this was before I had tube specs so ran them at 5 volts. I quickly learned the newest tubes drew the highest primary current,
Next I had to see what they did with plate current. I mounted a socket in a chassis with a blower. I put all grids to ground and put plate voltage on them. Again the best tubes had the highest resting current matching the heater test. I then built a final around the tube knowing at least one was good.
the rest is strap history.....and a fellow pickeled egg plant lover has my collection of 4-1000As spares.

[kf6pqt]

Ok... so, pardon my lacking basic basic knowledge of tubes...

So with a functioning tube you light it up, ground the grids, and current will be drawn... and its being drawn from the plate to the cathode? or vice versa...? Where does the plate current "go," in a test jig? just dissipated as heat? (then, obviously, raising the grids above ground potential would begin to block the current, that part I understand...)

Once I figure this out, the test jig will be easy.

They both have coffee stains... one with a little green sticker, one with a red, go figure! But I got the pair for thirty-some bucks shipped, so even if one is about shot its all good.

I potentially have 3 different amps/transmiters in the design phase... I'm trying to do proper dilligence in my research, but don't be shocked if i ask a whole bunch of questions about load impedance and output-network design pretty soon!

Thanks and 73,
Jason kf6pqt

[WA1GFZ]

The tube is acting like a variable resistor. Raise the grids above ground and you will draw a lot of current. I would thing a 4-400 in GG with 3 kv on the plate should draw about 60 ma. Center tap of the fil transformer goes to high voltage return (-).

[Steve - WB3HUZ]

I potentially have 3 different amps/transmiters in the design phase... I'm trying to do proper dilligence in my research, but don't be shocked if i ask a whole bunch of questions about load impedance and output-network design pretty soon!

I'd be careful going any further with the design until you get a handle on how tubes work. Suggest you get a ARRL or Radio Engineers handbook (anyone published from the 1940 through the 1960) and read it heavily, especially the chapters on RF amp design and tube operation. You'll get more coherent info than you ever could aksing questions here. Once you've read that material, if questions remain, ask here.

And the cool thing about getting that handbook is that you will use it again and again. It will be money and time well spent.

[k7yoo]

There is an article on a universal xmting tube tester in one of my old tube handbooks--I think RCA. I will take a look for you.
W0WG built one and has a universal socket panel set up for a a variety of high power tubes.
Skip

[kf6pqt]

I've got a stack of arrl handbooks from the mid-fifties, and one worthless one from '98. Got a couple of tube manuals, but from Late '60s, but mainly dealing with smaller tubes. Just won a Bill Orr Radio Handbook from late '60's off of ebay, heard good things about that one.

oh, and dozens of tube data sheet .pdfs!

I have been doing a lot of reading, but presently I'm just confused a couple things, likely I've understood something incorrectly and its thrown me off track.

Some new material ould be great, if anyone's got an extra copy of the Radio Engineers book, or an ebay link to one, it would be greatly appreciated!

Thanks and 73,
Jason kf6pqt

[WA1GFZ]

Or be crazy like the rest of and just keep your left hand in your pocket when you fire stuff up and learn by the school of hard knocks hoping you don't kill yourself first.

[W1RKW]

Ah, yes, the smokes and explodes approach.  I remember years back SAE audio equipment being nicknamed Smokes And Explodes.

[Rob K2CU]

Best bet is to:

1. Lite up filament and check for interelectrode shorts.
2. Find someone else with an amp using the subject tubes and check them for performance.

No joke, this is the best way. About 20 years back, a buddy in 4 land came upon a couple dozen RCA 8122's.  Since he knew I had them in my NCL 2000, he sent them up and I tested them, first by using amp with single tube installed to measure bias for 100 mA idle current in SSB mode.  I could only compare them to the pair I had in the amp originally, so I had determined the levle from the exciter to produce 1500W output on 20 meters. Then applied same drive for each set of his that I paired up.  They ranged from 1000W to 1600W, with most around 1500W.  He offered me a pair for my trouble, but I already had 10 good matched pairs of my own.

JS'ing any kind of test setup is far too risky and aint worth your life!

[kf6pqt]

Yeah, I'm just going to build an amp.   One of the old QST articles that floats around (Universal Amp) uses a grounded cathode, untuned input design that works with a 4-400. (or an 833a, droool)  Figure, the way one would most likely zap themselves is screwing around with a tuned input when getting the amp running, so I'll eliminate that pitfall.

Thanks and 73,
Jason kf6pqt