tube tester

JoshK · « **on:** 4 Dec 2005, 04:47 am »

Any of you guys have suggestions about tube testers? I am considering buying on and wonder if any of you have experience with them?
TIA,
JOsh

warnerwh · « **Reply #1 on:** 4 Dec 2005, 07:00 am »

Josh: There's alot of guys on the tubes forum at AA that have experience with tube testers. You may want to also ask Frank Van Alstine. He's been around since the 70's and knows what he's doing as well as anyone.

JohnR · « **Reply #2 on:** 4 Dec 2005, 09:22 am »

I have a TV-7. Unless something has changed in the last few years, I would suggest either getting something of this caliber, or don't bother. I went through a few duds (to "save" money) before settling on this one.

Bear in mind a few things. It won't test tubes invented since the 50s (40s?). EL509, the russian super-tubes, etc. They will often need a new rectifier. They only test at one plate voltage, which are probably nothing like the conditions a tube will experience in an amp. If you really want to match accurately, then you need a tracer or a home-built test unit that will test it a range of plate voltages and currents. (See Hagtech for a tracer.) Basically, a tube tester of this nature will give you a useful indication of the health of a tube.

HTH...

PS warnerwh, what is the point of telling people to go somewhere else? If you don't know, then don't just assume other people don't know!

GBB · « **Reply #3 on:** 4 Dec 2005, 12:57 pm »

I agree that Hickok testers are really good although prices seem to have gotten out of hand. I have a TV-7 and a 539C which I picked up before prices escalated. One thing to keep in mind is that a lot of these old machines would benefit from a good restoration and calibration. Once done they will last forever. I had my TV-7 repaired and calibrated by Dan Nelson out in Arizona who does great work for a very reasonable amount of money. I can provide contact information if you're interested.

A quick scan of ebay turns up a few items that might be of interest. This listing is for a TV7 and is in the New York area so one could pick it up and avoid shipping costs - these things are heavy.

http://tinyurl.com/bx3u9

This listing is for a 539 needing repair:
http://tinyurl.com/azhfp

You can probably get it cheap and then send it off for repair and get a great machine for a slightly more reasonable price.

And though I've not been good about attending the NY raves, I am in the general area and could be convinced to bring one of the testers along if you need something tested.

---Gary

JoshK · « **Reply #4 on:** 4 Dec 2005, 05:01 pm »

Jim's product looks quite slick. Looks like I need to read up a lot more before biting the bullet. Maybe I'll pick up a scope first. DIY isn't cheap!

Scott F. · « **Reply #5 on:** 4 Dec 2005, 06:13 pm »

I remember reading something, somewhere by one of the tube tester experts. Basically he said be choosey when it comes to a tester. Some of the testers out there don't apply full plate voltage (or maybe it was current, I forget) to the tube. Without this you can get false readings on the tube. Not necessarily whether the tube is good or bad but rather it has possible shorts.

I found this out the hard way with a rectifier tube that turned out being bad. I tested it on my Knight and it tested strong with no shorts. I installed it and within two minutes (after heating up) it flashed and took out a (rather expensive) transformer. I retested the tube on my B&K and sure enough, it tested bad.

As I remember, he mentioned that many of the older, tube rectified testers did a good job. They brought the tubes under test, to full voltage (and current, I think). I remember him mentioning the TV-7 and the B&K's as being some of the better testers.

Restoration is essential to get good readings. These things are loaded with old caps that need to be updated. Several critical resistors should be changed out with ones of tighter tolerance.

Boy, I wish I could remember where I read all that stuff at. Might have been over at the Tube DIY forum ?

JoshK · « **Reply #6 on:** 4 Dec 2005, 06:34 pm »

Scott,

Which B&K?

The Vacutrace is a bit steep for the DIY'er, but it looks like a really intriguing product. I wonder if there is anything that the Hickok and B&K can do that the Vacutrace can't? It is a total substitution?

Anyway...thanks guys. Food for thought.

jeffreybehr · « **Reply #7 on:** 4 Dec 2005, 08:08 pm »

"PS warnerwh, what is the point of telling people to go somewhere else? If you don't know, then don't just assume other people don't know."

WOW is THAT unintuitive IMO. Warner is HELPING. Someone asked for help and didn't say he/she has looked anywhere else.

JohnR · « **Reply #8 on:** 4 Dec 2005, 10:14 pm »

Josh, what exactly is it you are trying to do? A tester for one particular tube can be built quite easily with a few parts. If you have a variac you can also easily adjust the plate voltage to take different readings.

Most of the complexity in the Hickok testers is because they can test gazillions of different tubes and tube types. If you open one up they are a marvel of switching and wiring

JoshK · « **Reply #9 on:** 4 Dec 2005, 10:42 pm »

Well I am trying to test the following:

5687
7044
6SN7
6N1P
6N6P
45
300B
6CJ3
0D3-VR150

That is for starters, what I have on hand (well all except the 300Bs which I don't have yet). I'd like to be able to match tubes for differential designs.

JoshK · « **Reply #10 on:** 4 Dec 2005, 10:44 pm »

That said, I guess I need to understand a little bit more about how to test tubes so I can figure out how to use a Variac to do it. I don't have a varaic but they are sure cheaper.

Scott F. · « **Reply #11 on:** 5 Dec 2005, 12:59 am »

Josh,

I use the B&K 500 Dyna-Quick. It tests for MU also. These can be found on eBay for about $80 - $100 in decent condition. It will likely need to be restored. Trouble is, it doesn't do 4 pin tubes (2a3, 45, 300B and others). Thats why I got the Knight.

When it comes to the modern 6N1P and the other newer Russian/Chinese tubes, you'll have to figure out what the settings are because the older tube tester charts don't take into account the new tubes. The 6N1P tube is very similar to a 6922 or a 6AQ5 (I'm only partially sure on the 6AQ5, I'm going from memory). If you were to run a brand new one through its paces on a tester using the data sheets you get from Svetlana (or where ever), you can use that for future testing.

I'm not sure a Vaiac is what you need to test tubes. The Variac is used to bring gear up to line voltage (110v) slowly. Its nothing more than a big, powered, variable resistor that can handle high current (via the transformer). I use an inexpensive Chinese model that I got off eBay for $80.

When it comes to the Oscilloscope, those are a completely different animal. On the DIY side, they are useful in testing unproven designs. They will tell you if the circuit is oscillating at some ultrasonic frequency, you can look at the waveforms, test ripple, and many more things. You will need to add things like signal generators to your purchase if the scope doesn't have one integrated. Trouble with a scope, they are not intuitive. You almost need somebody to show you how to properly use one. Granted, there are online tutorials but there is nothing like a mentor to give you a hand.

I personally don't have a scope. For the building I do, where I am using established designs and schematics, I don't have the need for one. Even when you do minor changes to a circuit, you [normally] don't need a scope.

When it comes to whcih tube tester, I've got to agree with JohnR, go for the TV-7. Just like him, I've spent enough on testers to buy at least two of those damned things. One of these days I'll learn, trying to get a bargain on decent test gear isn't possible. You will have to buck up on a few items.

Oh, you'll need a good Fluke multi-meter too. Another cvool tool to have are the old capacitance testers (like a Heathkits and Eico's). You can use these to reform vintage caps (paper in oils) by increasing the voltage and power factor gradually.

JohnR · « **Reply #12 on:** 5 Dec 2005, 02:02 am »

The variac is so you can set the plate voltage. You still need a power supply between the variac and the plate, of course

I have a circuit in some archives somewhere, I'll try and dig it up tonight.

JoshK · « **Reply #13 on:** 9 Dec 2005, 03:35 pm »

Well, I haven't bought a tube tester yet, thought I'd get a o'scope first. I just pulled the trigger on a Kikusui 5ch 100mhz scope. Way overkill for my purposes but I read up and it seems that this is a great scope that hasn't yet shot through the roof like some tektronics. Apparently the 100mhz bw is great for tracking down oscillations if pioneering a new design.

So I am officially way nerdy. It came with the manual so hopefully I'll be able to figure it out. Paul said he might be able to show me some basics and maybe we can examine the waveform on the Felicia.

Celeste · « **Reply #14 on:** 10 Dec 2005, 01:39 am »

slight trouble with those fast scopes , they have an acceleration grid in the CRT . it makes the screen faster but it scatters the beam a bit so the trace is not as clear. yes its nice for hunting oscillation in frame grid tubes but you loose detail that you would have with a 20MHz scope on other work.

Celeste

JohnR · « **Reply #15 on:** 10 Dec 2005, 11:30 pm »

Hi, here is the basic circuit for testing a tube. You need to supply plate voltage, grid voltage (negative), and have a small-ish resistor to measure plate current:

Here is the power supply, there is not much to it. Note the pot to vary grid voltage. What I haven't shown here is that the two transformers are on separate AC input lines. Use a variac on the main supply transformer to vary the plate voltage.

Here it is an action:

The tubes are EL509 being tested at a relatively low (170V) plate voltage, for other tubes or conditions you would need to change the power supply accordingly.

HTH

JohnR

JoshK · « **Reply #16 on:** 10 Dec 2005, 11:35 pm »

Thanks John.

eico1 · « **Reply #17 on:** 10 Dec 2005, 11:59 pm »

that is an awesome setup John, what are the voltage/current meters pictured? Nothing in my collection of Simpsons.

steve

JohnR · « **Reply #18 on:** 11 Dec 2005, 07:22 am »

Hi Steve, thanks! Those are a "Weston 622 DC Volt Milli-ammeter." Last calibrated in 1974 and 1978, according to the labels inside