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Author Topic: Decided to get a tube checker  (Read 9994 times)
KA5ROW
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« on: December 23, 2012, 08:07:41 PM »

OK I decided to get a tube checker, now lets narrow down the possibilities. I want to test tubes form the late 50's to the last made in the early 70's. I know the  mutual conductance testers are the best, and the Dynamic Mutual Conductance are kinda sort of  mutual conductance but not really,  but if most of the tubes are in receivers or not the actual transmitter finals the others should do fine for about 80% of what you test as long as you have a good calibrated tester.

Looking at the following:

Hickok 939- B or C if I can afford a good one. mutual conductance tester
Hickoc 6000-B  mutual conductance tester


Mercury 2000 Dynamic Mutual Conductance

Jackson 648-S Dynamic Mutual Conductance

Sencore Continental MU 140 Mutual Conductance

B&K 747 & 707  Dynamic Mutual Conductance because they are the most current / newest of the bunch.  Late 60's to 70's manufacture time frame

But in the real world I may settle on the Hickoc 6000-B  just because it's a Hickoc. Or the Mercury.

Am I leaning in the right direction?
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KE3WD
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« Reply #1 on: December 23, 2012, 08:32:33 PM »

Sure.
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KB4QAA
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« Reply #2 on: December 24, 2012, 11:29:36 AM »

I've got a Jackson 658-1 from about 1968 that was top of the line and end of the line as well.  Tubes seem to perform in circuit generally in relation to their measurements.

**Regardless of what brand, model or test method used, ensure that you have full documentation available; schematics, tube lists, updates, errata sheets, seldom used tube lists, and any accessories like adapters, jumper cords, etc.   The nicest tester is useless without them. 

*From the hardware perspective, be sure the tester meets your needs.  You don't want to end up with a late model guitar or TV tester, when you are heavily into early boat anchors and need some of those big tube sockets.   Almost no testers can check transmitter tubes for anything but shorts, if that.

Platitudes and Attitudes:
-"If it ain't a Hickock, it's only good for selling tubes to gullible customers"  Tongue
-Regardless of the brand or method, no tester can guarantee tube performance in any given circuit
-Even if you don't have the top of line tester ever made, whatever you get will help take some  guess work out of trouble shooting, and help in sorting tubes.  I find it helpful to test several tube of the same type to compare the one in question, and then swap them out in circuit. 
-Be sure to overhaul your tester like any boat anchor restoration.

73, bill

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K1CJS
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« Reply #3 on: December 25, 2012, 07:00:41 AM »

You can say what you want about tube testers, but there isn't a tube tester out there that will compare to the best way of testing--substitution in the circuit the tube is intended to go in.  The tube tester just can't duplicate the exact conditions that the tube will have to operate in.

The only thing most tube testers will do is to check for shorts.  Others may check minimal operating conditions, but nothing more.  That was taught to me by an old time TV repairman--someone who could practically overhaul a TV right in the home and get it working properly no matter what was the problem with it short of having physical violence done to it!
« Last Edit: December 25, 2012, 07:03:43 AM by K1CJS » Logged
AA4PB
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« Reply #4 on: December 25, 2012, 07:17:34 AM »

Quality tube checkers check for open filiments, shorts, and test for gain at low frequencies. Any tube that is operating at RF or IF frequencies can have defects that don't show up with a tube tester. It was always standard practice to substitute new tubes in these higher frequency circuits if a problem was indicated there.

The value of a tube tester I suppose depends on how many old radios you are trying to restore. If you are restoring only one or two then you are probably better off just purchasing a new set of tubes and replacing them all.
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K8AXW
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« Reply #5 on: December 25, 2012, 08:17:37 AM »

Tube substitution is no doubt the way to go but with today's tube prices, this isn't such an attractive option as it once was.  

If you have only one radio..... yes, but if you have more than one..... or if you like to work on boatanchors then the tube tester becomes more attractive.

I was given a Hickok many years ago and I still find it nice to be able to go through 25 tubes in a boatanchor before investing money in new caps and resistors.  

One good thing is, after the investment, you don't have to feed it!   Grin

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AC5UP
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« Reply #6 on: December 25, 2012, 09:10:37 AM »

I've repeated this story before but I think it's worth hearing again... " Great Moments In Technical Education "

Many moon ago at a large Technical Extension School  (we don't call it the Vo-Tech any more)  it was not uncommon for local industries to donate large piles of fully depreciated test equipment for one last tax writeoff. In one of these piles was a fairly nice Tektronix 500 series 'scope which had a few problems. An electronics instructor tasked two of his allegedly brightest students to start the diagnostic process by testing all the tubes on the lab tube tester.

All tubes tested bad.

The instructor didn't believe this was possible, quizzed the students about exactly how they were testing the tubes, and concluded their next challenge should be to troubleshoot the tube tester. Soon after removing the back cover the students discovered two tubes inside the tube tester. These tubes were removed, the tester placed upright on the lab table, then the tubes from the tester were checked on the same tube tester.

Both tubes were bad.

The students were pleased that they had found the problem with the tube tester so quickly.
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KB4QAA
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« Reply #7 on: December 25, 2012, 12:36:21 PM »

Counterpoint:

-There is something to be said for not using your precious boat anchor as a sacrificial tube tester for your giant tube collection.  Wink

-The numbers a test gives you are at least a quantifiable starting point for evaluating tubes, and probably better than sticking them in a circuit and trying to divine 'how well' they are working.
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K1CJS
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« Reply #8 on: December 26, 2012, 04:27:18 AM »

KB4QAA,  Point made--and accepted.  A tube tester is good to make sure that a tube isn't shorted, but the counter-counterpoint (we could keep at this all day  Cheesy) is that even if a tube checks OK on the tester, it could well still damage the boat anchor when its put into actual use--especially the transmitter final tubes of those precious boat anchors. 

I guess that its just the way things are with the scarcity of tubes these days and the having to reuse some of the older ones that we have or can get.  73!
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G3RZP
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« Reply #9 on: December 26, 2012, 06:07:57 AM »

You also have to be a bit careful with so called 'new' tubes. Some 6BA6 made in Poland actually have suppressor grid and cathode tied internally, so in a circuit with the suppressor grid tied to ground, you lose the grid bias.
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KD0REQ
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« Reply #10 on: December 26, 2012, 08:05:07 AM »

there are some internally fragile tubes that short if you look at them funny... the same audio tube used in the Heath SB/HW series is used in some Hammond organs.  looky here, they are prone to shorting suppressor to cathode. that burns up the limiting resistor if any, the rectifier, and the power transformer.

there are also a bunch of NOS tubes that have gassed up over the years, but sitting in the tester socket for a while can degas them.

two excellent reasons to have a tube tester.  and it's not necessary to have one box to test them all, and in the caddy bind them, if you get a newer tester and an older one at the right price.
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KD0FAT
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« Reply #11 on: December 26, 2012, 04:40:52 PM »

There are two basic types of tube testers out there.  The most basic type is the emission tester--and they should be fairly cheap on the used market. Of course, all tube testers available today are used!! The emission tester will tie the control grid, the screen and the plate together and apply a positive voltage. The cathode is then made negative. We now have a simplified tube that is essentially a diode. If the heated cathode is still able to produce enough free electrons to flow through the vacuum to the +biased elements, then the filament/cathode part of the tube still has enough guts to do the job. This does give you some good information about the usefulness of the tube.

The more sophisticated "dynamic mutual conductance" tester, Hickock being a good example, attempts to test the tube in a more realistic circuit. The tube is set up with appropriate bias and plate voltages on its separate elements. A 60 cycle signal taken from the line voltage is used as a signal on the control grid. The meter then indicates the current flow in the plate circuit, with the tube acting as an amplifier.

The Hickock testers are more expensive than the emission type testers. Hickock equipment is very well made. I have a model 532 that dates from about 1948. After I replaced two internal capacitors that were leaky, it works very well. A Hickock tester will tell you if a tube has a good filament, if you have internal shorts, if the tube is gassy, and if it will function in an amplifier circuit.  An emission tester will tell you if the filament/cathode element can still produce enough free electrons for tube function.     

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IZ5PQT
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« Reply #12 on: December 27, 2012, 08:06:01 AM »

Grin You can quickly and cheaply test tubes for emission using just an AC transformer and a rheostat: see my page http://www.televideo.ws/tubes.html (the table was taken from some old magazine). It's very good
to compare tubes.

73 Giovanni
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W7GIF
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Posts: 126




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« Reply #13 on: December 28, 2012, 11:40:28 AM »

OK I decided to get a tube checker, now lets narrow down the possibilities. I want to test tubes form the late 50's to the last made in the early 70's. I know the  mutual conductance testers are the best, and the Dynamic Mutual Conductance are kinda sort of  mutual conductance but not really,  but if most of the tubes are in receivers or not the actual transmitter finals the others should do fine for about 80% of what you test as long as you have a good calibrated tester.

Looking at the following:

Hickok 939- B or C if I can afford a good one. mutual conductance tester
Hickoc 6000-B  mutual conductance tester


Mercury 2000 Dynamic Mutual Conductance

Jackson 648-S Dynamic Mutual Conductance

Sencore Continental MU 140 Mutual Conductance

B&K 747 & 707  Dynamic Mutual Conductance because they are the most current / newest of the bunch.  Late 60's to 70's manufacture time frame

But in the real world I may settle on the Hickoc 6000-B  just because it's a Hickoc. Or the Mercury.

Am I leaning in the right direction?
My favorite is a Hickok AN/USM-118, although I'm missing a few of the programming cards. As a result, my TV-7D/U and 539C get the most use. I've found the TV-7 to be a pretty dependable tester for most tubes, and a whole lot more "portable" and bench-friendly than the AN/USM-118 (or the 539C).
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AJ4CU
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Posts: 78




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« Reply #14 on: December 28, 2012, 05:44:07 PM »

Hickok 539C!

Would never part with mine....

Of all out there this is at the top of the list...TV-7 next....

600, 800 and 6000 are ok...
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