Tube Testers

[ALL212]

It's winter...I'm bored...have tubes...hmmm...

Appears to be a boat load of tube testers on the 'bay.  Anyone have recommendations?  I've got the usual 9 pin assortment, have some 6080's types, just got into the 2A3's, probably will play in the 6DN7 line.

I know it should be calibrated but there is a guy in Chicago (close) that can do that.  I just don't know a thing about them but would like to figure it out.

Thanks!

[Doc B.]

A TV-7 or TV-10 is among the most versatile. They are also pretty expensive these days. I love to brag that I got my TV-10 for $50 back in the early 90s.

The old hardware store tube testers are fun. Not as accurate, but easy to use and they make great conversation pieces if you have the room. And you can store a fair number of tubes if you get one mounted on a matching cabinet. I had an old Mercury in my home lab for a few years.

The B&Ks are pretty nice too, though IIRC not transconductance testers. Whatever tester you buy be sure you get one that is new enough to be able to test the later nine pin tubes.

[Tubejack]

I had a Hickok 600, which is compact, you can find them reasonably priced, and they test  the majority of the popular audio tubes.  I upgraded to a 539C when I found one reasonably priced and in VG condition.

[caffeinator]

I have a Hickok 6000, which is nice, though it does not have a 4-pin socket.

Since I needed a tester w/ a 4-pin socket, I was looking for something else.  TV-7's have gotten too pricey.  I did find a good alternative - an I-177.  It doesn't do everything, but it will cover my 4-pin DHT's and between that and the 6000, most anything I need can be tested.  They also go for a lot less than the better-known models (or at least it did when I got mine).

[johnsonad]

I have a B&K 747 and really enjoy it. It doesn't do the 4 pin tubes but is SS and easy to cal.

[Listens2tubes]

What tester did you get or are you lusting over. I have a Hickok 533A, B&K 747 and 700 and Mercury 1000 mutual conductance testers. I use the 533A  and 1000 more than the others. THe 533A shares its tube chart with the 600A and 800A IIRC. The Mercury is compact and very nice to use.

[mcandmar]

http://www.ebay.co.uk/itm/260937142913?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Since you all seem a knowledgeable bunch in this area i would be interested to hear your opinion on this DIY tube tester kit.  It seems versatile in that you can set plate and grid voltages and then measure the output current. I am interested to know if its measurement output is sufficient to gauge a tubes health, and to match sets.  Or are there other properties to a vacuum tube a real tester can measure that this cant.

Obviously its not a complete kit as you need to provide a low voltage DC input and heater/filament supply and an enclosure with tube sockets but that's easily done.  Does it look like a worthwhile project?    I've attached a copy of the documentation the seller has provided.

[Grainger49]

I couldn't read much in the description.  The checker will accept octal and noval tubes only.  So 300Bs and 2A3s are out.

Hopefully the readout will give you help setting the bias and B+ for each tube and in the "test" position give you a reading.  Does it come with the setup and target data for tubes?

[mcandmar]

The kit doesn't come with the sockets, they are just shown as an example. In theory it could test any tube, all you have to do is wire in a socket of your choice.  From reading the manual you set voltages using the two pots, values are displayed on the LCD.  Then when you press the test button it tests the tube and measures its output current. The manual just states you take the test settings from the tubes datasheet. From there i am a little grey on the subject.

The definition i have found for transconductance states "transconductance is the ratio of the current change at the output in relation to the voltage change at the input", so i take from that if you apply the recommended plate, grid voltages as per the datasheet you should get X current output.  I can see that working fine to match tubes, but to test the health of a tube is it as simple as pulling the current to voltage ratios from the charts in the datasheet?

[mcandmar]

Update: I ended up buying the eBay board listed above and thought i would share my thoughts as it may be of interest to others.

The basic kit includes the circuit board, LCD display, two pots, momentary push switch, and a neon indicator. http://www.ebay.co.uk/itm/260906425038

The PCB requires 9-11vac so i used a dual tap 5v transformer wired in series for 10v.  For the heater supply i bought a 6.3v 10va transformer from the same seller. http://www.ebay.co.uk/itm/261321178012

The tube sockets, enclosure, and everything else you have to do yourself.  I built mine to test 6DN7, 12AU7, and 1S4/3S4 family of tubes.  Testing just about any tube is possible once you build a suitable heater supply and wire up the socket.

How does it work?   Step 1: You power up without any tubes and set the Plate voltage and Grid voltage using the two pots.  For the values you can either use the "average characteristics" values listed in the datasheet, or look at the "average plate characteristics" chart and pick the voltages you want to test at.  Step 2: Plug in the tube and power up again and give it a minute or two for the tube to warm up and press the "test" button to measure the output current.

In terms of accuracy it seems very close to the datasheet values, generally a healthy tubes reads slightly higher. All the 6DN7 tubes read higher for Section 2 so i'm not convinced about the datasheets accuracy there, or maybe i'm reading it wrong which is entirely possible. Here are a few examples..

3S4: Datasheet average characteristics state: 67.5v plate, -7v grid = ~7.2-7.4ma

Six tubes tested were all ~8-9ma.

6DN7: Datasheet average characteristics state: Section 1: 250v plate, -8v grid = 8ma  /  Section 2: 250v plate, -9.5v grid = 41ma

Six tubes tested were all ~8ma for Section 1  /  ~60ma for Section 2.  A known bad tubes tested 5.9ma / 57ma.

I forgot to write down the values for the 12AU7's but i do remember a new Chinese tube measuring something like 15ma/8ma instead of the nominal 10.5ma listed in the datasheet, and a Brimar was 9.5ma on both sides. A crack owner could literally drive themselves crazy looking for tubes that match on both channels

Conclusion: A very versatile bit of kit that allows you to test the health of a tube, match them yourself, and plot the characteristics if you are so inclined.  Most important for me was its a fraction of the cost of a real tester, overall i estimate it cost me ~€120 to build so great value for money, and a fun project too..

[Doc B.]

IIRC the two 6DN7 triode specs are swapped in the RCA manual.

[JamieMcC]

That looks a interesting project, Im not sure why I did not see the earlier posts with the *show new post function* but pleased its now showing.

[mcandmar]

IIRC the two 6DN7 triode specs are swapped in the RCA manual.

Now that i look at it again there is a section in the datasheet that specs 150v plate, 0v grid = 68ma.   68ma does seem to make more sense than 41ma so i assume its those two sections that are reversed?

The actual graphs seems to concur with 41ma though.  I am looking at the GE datasheet as its the only one i could find with the charts, and the 6FJ7 GE and RCA datasheets are identical in that respect.

[Snarii]

Hi,

exploring the shop you mentioned, I've found another kit that might be of interest :
http://www.ebay.co.uk/itm/MODULE-TRACEUR-DE-COURBES-LAMPEMETRE-ANALYSEUR-VACUUM-TUBE-ANALYZER-/260948674688

This one is piloted by a PC and can measure and generate families of voltage-current curves.
It requires 3 power sources : 24V, heating + plate high voltage (330V max)

Attached is the french user manual