Tube Testers?

Well, having easily half a dozen tube testers in my shop may suggest that I am biased, but really, how can you NOT have a tube tester if you are using tube equipment? Short of having only a few tube devices, and knowing what the parameters should be for each tube in those circuits if working properly (resistors good too!) so that you could use a volt meter only, a tube tester can take a lot of the guesswork out.

Mutual conductance testing is ideal (and most expensive type of tester) and the drug-store go/no go testers are at the bottom. The decision is driven by your budget and how often you are likely to need the thing.

If you are frustrated when trying to fix an amp or radio because you don't' know if the tube(s) are the cause, then you need to spend the money.

Tube testers are quite robust, so they rarely need service. Usually just a switch or tube test socket goes bad so pretty easy to deal with.

Get schematics for whatever tester you choose!

Oh, and get a scope at the same time. And a signal generator. And a cap tester...

John :-#)#

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                      John's Jukes Ltd. 
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 
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--------------------------

** IME - no use at all.

In 50+ years of working with valve gear, I have never used one and know no-ne here in Sydney who does.

What you NEED is a supply of known good valves to use as substitutes.

The item itself is your "tube tester" and a far better one that anything you can buy - cos it operates the valves under *actual service conditions*.

Others here will say differently, cos they own one of more of the stupid things and *love* them irrationally, like pets.

FYI:

Not long ago, I designed a special power valve tester that, along with a few common bench items, allows operation of audio power valves under realistic and even more severe conditions with *everything* adjustable.

It can both sort out tubes with ANY kind of fault and match sets under conditions as found in commercial amplifiers as well.

Nothing on the market like it exists, anywhere.

Cos me SFA to make too.

.... Phil

..... Phil

I have a few, but usually just to satisfy my curiosity.

An excellent bit of kit sir.

--
"I am a river to my people." 
Jeff-1.0 
WA6FWi 
http:foxsmercantile.com

If you will be repairing anything with vacuum tubes, then you need a tube tester. I suggest a mutual conductance tester. Mine is a Jackson model 648. It has a built-in scroll of setting information for many older tubes.

You will occasionally find these on E-Bay or at a Hamfest.

I don't think they are that complicated. Just a simple circuit with a BUNCH of switches and tube sockets wired together. The meter is marked in percent, so you can see how relatively good your tube is.

At some Hamfests, I've seen "calibration tubes" that you could use to check your 100 percent adjustment. I never worried about mine, since I just want to know if a tube is relatively good. Suppose it is only reading 75 percent. That is still a useable tube if you don't have a replacement.

Fred

------------------------- Phil Allis>

** Nice of you to say so. FYI:

My colleague Rod took a few liberties when he edited my submitted article.

He added extra circuits of his own, that he had merely simulated and did not build - he has never seen the prototype shown in the pic that I use here.

Mine is very simple, it uses only external PSUs - the 6.3V comes from a variable 5A DC bench supply and negative bias from another 2A one.

There is no "test" button as there is an on/off switch on the front of my 240/240 isolation tranny.

The only known trap is if you hastily hot switch from from pentode back to triode mode - as the latter requires way more negative grid bias. Normally just pops the fuse.

I soon found that most 6BQ5s could be pushed way more than usually seen in pentode mode - with plate and screen voltages of up to 640V and 320V respectively.

So I built a simple output stage that employed a push-pull pair that way and got a remarkable 60W rms of clean power with no sign of red plating !!

Having long ago gone through all my junk box valves, the tester is mainly used for brand new ones, soon as I get them, in case I find a dud or one well out of match. I have even had one or two with the glass broken !!

If I need to return a bad valve, there is way less hassle if I do so the same or next day.

I also added a banana socket to the rear of the box allowing a short top cap lead to be fitted for types like the 6CM5 and 6DQ6B. A few Aussie made guitar amps from the 1960s used them.

.... Phil

The tube tester is not of very much use, especially to someone that is not in the repair business. For those that are, they will usually have a stock of new tubes and it is quicker to just pop one in to see if it solves the problem.

There are 2 basic types in common usage. One is the simple emission tester. It connects most of the elements together except the cathode and checks as to how much the cathode will put out. That will often tell if the tube is weak. The other is the mutual conductance tester. It simulates a circuit and is better.

Most have a shorted element test where you plug in the tube and tap it.

They do not usually need calibration. The easiest way to tell is to check several new tubes and see if they show way up in the good reagon.

Tubes are usually the last components to go bad unless another component causes them to go bad or the filament opens up which an ohm meter will tell.

I already have a Tek 465B and a BK 4MHz function generator. No cap tester yet. Eric

If you can find an old EICO or Heathkit component tester (Resistors/Caps/Inductors - using a Wheatstone Bridge) with the "Magic Eye". They are great for reforming caps (they go up to 600V if I am not mistaken) and the Magic Eye is a nice touch.

John :-#)#

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(Please post followups or tech inquiries to the USENET newsgroup) 
                      John's Jukes Ltd. 
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 
          (604)872-5757 (Pinballs, Jukes, Video Games) 
                      www.flippers.com 
        "Old pinballers never die, they just flip out."

You may want to look into getting one of the roughly $ 20 component testers from China. They do a good job of testing many solid state devices, inductors, capacitors and resistors. Plenty of them on ebay.

Very handy little things. No reforming function as yet. You never know it might appear one day, but I'm not optimistic. And the one I have can't do in-circuit testing, nor C versus V info. But it does give C, ESR & loss with a single button press.

NT

Won't be easy to reform caps without a wee bit more voltage than a 9V battery can supply. Besides, if a cap needs reforming, it's best to not use it.

You never know it might appear one day, but I'm not optimistic. And the one I have can't do in-circuit testing, nor C versus V info. But it does give C, ESR & loss with a single button press.

I bought one because I couldn't resist it for the price, but I find it wildly inaccurate for low value resistance and low value capacitors. I found a calibration procedure on-line that uses a small value cap for a reference, but it only made it worse.

Does identify terminals in transistors accurately though.

a non-challenge to step it up onboard.

No-one would accuse them of being quality items, but very handy nonetheless. I hear there is a new version now & then with ever more functionality.

NT

What is interisting is a company called Peak makes several versions for around $ 100. The cheat people that are not informed. One device only tests the solid state devices and the other tests restiors, capacitors and inductors. That way you are forced to buy two of the units.

They are practically the same as the all in one $ 20 device in a fancy case.

They are not lab quality instruments but for $ 20 they work very well at the hobby grade.

As far as forming capacitors, if the capacitor is over 20 years old and there is any doubt, just replace it. I have read that new capacitors are formed at the factory at a slightly higher voltage because they will deterioate just sitting on the shelf. Those may be worth while bringing the voltage up slow on if they have been on the shelf for a long period of time

t wildly inaccurate for low value resistance and low value capacitors. I found a calibration procedure on-line that uses a small value cap for a ref erence, but it only made it worse.

less. I hear there is a new version now & then with ever more functionality .

A lot of people have that approach. Whether replacing sound historic caps w ith new ones that likely won't last is a good plan is debated.

same happens to old caps. Doesn't mean they're dud.

NT

RANT WARNING!

On tube testers - with the exception of very modern testers that will plot curves on a PC, effectively there are two types of testers and within each type, two tiers.

A top-tier emissions-tester is good for 99-44/100ths of most hobby uses. It is, for the record, very nearly as good as a second-tier GM tester. Better in some few cases.

A top-tier emissions tester will also test (reasonably accurately) for "SHO RTS" and "GAS" - which functions are what separate a tester from the device itself. Reject any tester out of hand if it does not do shorts and gas. It is useless in actual practice. A Heath TC-2/3 and many others will meet t he most basic needs of the hobbyist. Prices for Emissions-Only testers are, perhaps, 20% of the price of a GM tester, all other things being equal.

A standard GM tester will also test for shorts and gas - some better than o thers. By virtue of being a GM tester, such a unit will give a >RELATIVE< i ndication of actual tube quality against a narrow set of fixed parameters. That information is very nearly useless *unless* one has known-good tubes w ith which to compare readings.

Now, a top-tier GM tester (and there are very, very few) will allow one to set bias, read filament current, plate current, and - thereby - allow one t o actually match tubes accurately. An example of such would be the Hickok 5

39 series. But NOT (emphatically) a TV7, however popular and expensive it m ight be.

Unless one is seriously into audio and has an actual need to match tubes an d/or do qualitative testing, don't waste your money on such a tester. And, if one is as deeply in as all that, look into the modern testers with curve

-tracers and so forth. Big bucks. Or, if, as I did, you should trip over a fully calibrated 539B, grab it. But, at the going rate of $1,000 and up, no t so much.

Now, on WHY:

A tube with a short - especially a thermally dependent short can do great h arm if it fails in-situ and without the operator right there with the insta nt shut-down device. A slagged rectifier tube, for instance, can take out a power-transformer in seconds. And why it is that a certain tubes should be tested for some time on a tester to look for thermal faults. Open filament s are seldom a threat, but shorts really, really are. And, a thermal short will NOT show up with a VOM testing at the pins.

A tube tester is handy. It allows one to develop a stock of good, trustwort hy tubes such that when 'at work' one may simply substitute-and-test-later without agonizing. One also avoids cascade-effects, where a series of weak tubes give symptoms not attributable to any one (or two) tubes. A good exam ple of such would be a multi-band radio that is perfectly fine on AM, but w eak on SW, or silent on FM, if so-equipped.

So, Eric, out there on your island - if you want a tube tester, DO NOT go o ut there on eBay. DO go either to a trusted dealer - there are several - an d expect to pay a premium for a good, clean, warranted device. OR, go to a trusted friend who is more in harm's way than you might be, and use him/her as a bird-dog for you. At Kutztown, there are never less than 30 - 50 tube testers on-offer, of which more than 80% of them are not worth the cost of plugging them in. Of the remaining 20% most of them are too much work to m ake reliable. Of those few remaining, they can be gems. But, I would guaran tee that if one were to attend two sequential events, and have a budget of $200 or so (inclusive of shipping), one would wind up with a fully function al device with the correct literature to cover most of the tubes you will e ncounter in this hobby.

End Rant

Some other points:

a) An individual primarily working with instrument amplifiers as an example , will have a very limited universe of tubes to test. For that individual, a full-range tester will be heavily compromised due to its all-things-to-al l-people requirement. That person needs a specialty tester. Those who routi nely use, maybe, 10 kinds of tubes, but whose collection uses well over 200 kinds of tubes might be a bit hamstrung by a specialty tester.

b) There are those here that are genuinely dangerous, and should be strung up by their thumbs from the nearest lamppost for the advice they give. Have the wisdom to discern the issues involved.

c) And there are those here with specific prejudices, peculiarities and exp ectations - some more hostile than others. I more-or-less fit into this cat egory at times. Same advice as above.

Peter Wieck Melrose Park, PA

And still, you persist in this stupidity. Quality electrolytics these days are quite reliable and long lived. Unless you're buying cheap counterfeits from China.

I've been repairing (which includes blanket recaps) for the past 25 years now, I have yet to have a customer bring back a radio because a cap failed.

Which is exactly why I do what I do.

--
"I am a river to my people." 
Jeff-1.0 
WA6FWi 
http:foxsmercantile.com

That's one side of the recap all or not debate, and of course new caps don't fail in short order. The OP is free to find out why some of us don't do that. I tire of your stupidity.

NT

Bwahahaha, I could have sworn you kill filed me dear. Obviously you lied about that too.

Let's see how you talk your way out of this.

--
"I am a river to my people." 
Jeff-1.0 
WA6FWi 
http:foxsmercantile.com

The answer is obvious. You're hack. Too lazy to do a job correctly and you find infinite ways to justify your position.

--
"I am a river to my people." 
Jeff-1.0 
WA6FWi 
http:foxsmercantile.com