Tube tester

[leakstereo20]

I have read some of Mike Rowe's thread about his superfine tube-tester, and the circuit seems to be just a little too complicated for me.
I have tried to simplify some of the ideas found from "Funke W19" and other tube-testers.

There has been many thoughts of a simple diy test setup for the most common 6,3V E-types / 12A.. types .
The "Nos" 12AT7 Telefunken does it "leak"oxygen , or the two triodes...do they match?

As far as I understand the tube-data-sheets, +310V on the plates of a KT66 or KT88 is not sufficient to determine a close match, but this voltage will have to do it ....because this is the voltage available! Both voltages + high and negative - minus have to be regulated.

Any simple ideas to the set-up schematic for ECC83 , 6SN7 and EL34 would be highly appreciated.

Two PSU's attached high voltage +300Vdc and neg. -120Vdc....DC heaters.

Schematic set-up link for ECC83, ECC82, ECC81, 6SN7 , EL34 :

https://picasaweb.google.com/1031761...22949922722402

https://picasaweb.google.com/1031761...35953886498290

https://picasaweb.google.com/1031761...36760178462642

rgds. Kim

[Leon Crampin]

I would regard an isolated power supply on a valve tester as being absolutely essential.

Leon.

[leakstereo20]

Originally Posted by Leon Crampin

I would regard an isolated power supply on a valve tester as being absolutely essential.

Leon.

I assume that you mean two different powertransformers for each regulated supply? May be a third transformer for the DC-heaters....or did you refer to isolated supplies to be activated by use of optocouplers?

I had in mind that different transformers for the two supplies, high B+ and -Ug1 would be sufficiant? The risk to destroy anything when one tries to measure a double triode tube, should be reduced by use of shorting free contacts connecting from one triode to another. Don't you agree?

Kim

[Ed_Dinning]

Hi Kim, a single transformer will do the job but may be quite large. The idea was that all windings should be isolated from the mains (no AC/DC techniques) and you may have to use several windings all isolated from each other, not a simgle winding with many tappings.

SMPS supplies may work but I would be wary of any EMC being generated.

Ed

[leakstereo20]

Originally Posted by Ed_Dinning

Hi Kim, a single transformer will do the job but may be quite large. The idea was that all windings should be isolated from the mains (no AC/DC techniques) and you may have to use several windings all isolated from each other, not a simgle winding with many tappings.

SMPS supplies may work but I would be wary of any EMC being generated.

Ed

Hi Ed,
Thanks for your advice.
I do have two high voltage transformers, and on each transformer there are three separate secondary windings, 220Vac / 200mA, 12Vac / 1A and 6,3Vac / 3A. ( a transformer for a pair of EL84 I think).
If I only measure one valve like EL34 at the time, I think the transformer is capable to do the job. I might have to add another transformer for the negative voltage... with a voltage doubler on the 12Vac winding I could reach approx -32-33V, which is enough for EL34 and KT66 up to +300V...hmm?

As far as I have read and understood the notes, all EI transformers generates Electromagnetic Compatibility.
If electronic equipment are disturbed by, for example, static electricity, radio transmitters, computers, machinery, lightning or magnetic fields, there is a noise problem.
For us making homebrew equipment I think, that we have to live the fact that our amplifiers ect. conflicts with the law about EMC

My concern is the rather expensive milliampere meter....I have thought about two pcs. of 1N4007 with polarity against each other and across the terminals of the meter...taking care of eventual spikes??

Kim

[Ed_Dinning]

Hi Kim, yes they should work.
If there is space between the windings and the laminations of the transformer it may be possible to add turns for the bias winding with thin insulated wire in there. (wind 20 turns, measure and scale to voltage needed).
No need to stop at a voltage doubler, multiplication by 3 or more is also possible to get the voltage you need.
It is worthwhile fitting a mains input filter on equipment such as this and to use paper/ plastic caps of about 0.1uF in parallel with e-caps for better HF performance.

The anti-parallel diodes across the meter are also a good idea.


Ed

[leakstereo20]

Originally Posted by Ed_Dinning

Hi Kim, yes they should work.
If there is space between the windings and the laminations of the transformer it may be possible to add turns for the bias winding with thin insulated wire in there. (wind 20 turns, measure and scale to voltage needed).
No need to stop at a voltage doubler, multiplication by 3 or more is also possible to get the voltage you need.
It is worthwhile fitting a mains input filter on equipment such as this and to use paper/ plastic caps of about 0.1uF in parallel with e-caps for better HF performance.

The anti-parallel diodes across the meter are also a good idea.


Ed

Hi ED,

There are space between the windings and the laminations of the transformer, and I do have isolated cobber for the extra windings.

Would you prefer to add more windings to the 12Vac secondary section on the transformer, or make a mulitiple "C-pump" (tribler or more) to reach the sufficiant negative voltage? ....thinking...do we have a more "safe" ampere supply by adding more windings to the transformer iron compared with the voltage doublers?

I shall remember the high frequency capacitors in parallel with the electrolytic's. I normally uses the Wima polycarbonate or polypropylene types in my homebrew amplifiers.

Kim

[Ed_Dinning]

Hi Kim, extra winding is best; voltage multipliers, especially at low frequency have poor voltage regulation as the number of stages increases.

Polycarb etc should be fine.

Ed

[leakstereo20]

Originally Posted by Ed_Dinning

Hi Kim, extra winding is best; voltage multipliers, especially at low frequency have poor voltage regulation as the number of stages increases.

Polycarb etc should be fine.

Ed

Hi Ed,

I have already found some appropriate cobber wire thickness for the extra windings .
To complete the check-up of the E-valves I/we need to know a little more about mu and gm. There are a lot of information around which explains the tubedata , but I need to find out how to get presize measurements of a new and a used tube.
The tubetest " go or no go" is ok, but complete tubedata curves is better.

Thanks for your advice

Kim

[G8UWM-MildMartin]

Originally Posted by leakstereo20

I have read some of Mike Rowe's thread about his superfine tube-tester, and the circuit seems to be just a little too complicated for me.
rgds. Kim

Hi Kim,
I beg to disagree in as much as Mike's design is very straightforward yet rather elegant and, especially with Les's (Topcap's) enhancements, better than most commercial instruments, and any significant simplifications would save very little money.
You have probably already found the most expensive parts are the transfomer(s), meters, case, valveholders, and switches: The electronic components are relatively very cheap!
On the other hand, if you have a circuit you are comfortable building, then why not?
You could always add additional features at a later date at very little cost once you have the basic design working properly.

[leakstereo20]

Originally Posted by G8UWM-MildMartin

Hi Kim,
I beg to disagree in as much as Mike's design is very straightforward yet rather elegant and, especially with Les's (Topcap's) enhancements, better than most commercial instruments, and any significant simplifications would save very little money.
You have probably already found the most expensive parts are the transfomer(s), meters, case, valveholders, and switches: The electronic components are relatively very cheap!
On the other hand, if you have a circuit you are comfortable building, then why not?
You could always add additional features at a later date at very little cost once you have the basic design working properly.

Hi Martin,
I have to admit that Mike's design looked very complicated the first time I saw it, but a second view on his schematic made the curcuit look "more accessible" for me.
I like to understand the whole circuit before I start, and unfortunately I found Mike's schematic too late.
The tubetester set-up I had in mind will have to do it ...at least to a start.

Kim

[Ed_Dinning]

Hi Kim, unfortunately most valve data books only have strings of characteristics at a set voltage available. The place to look is in the internet (try googling the valve number), or look out for manufacturers valve data books that are normally supplied with curves.
Most totally comprehensive data is no longer available as it was supplied to designers from the valve manufacturers. This would have lifetime curves as well as characteristic curves plotted for unusual applications such as pulse use and amp use when driven by G2,

Ed

[leakstereo20]

Originally Posted by Ed_Dinning

Hi Kim, unfortunately most valve data books only have strings of characteristics at a set voltage available. The place to look is in the internet (try googling the valve number), or look out for manufacturers valve data books that are normally supplied with curves.
Most totally comprehensive data is no longer available as it was supplied to designers from the valve manufacturers. This would have lifetime curves as well as characteristic curves plotted for unusual applications such as pulse use and amp use when driven by G2,

Ed

Hi Ed,

Some time ago an acquaintance of mine donated me several old tube data pocketbooks from Philips and from "technische daten AEG - Telefunken". Much can be said about our German friends, but the discipline called precision is one of their forces. Each and every tube mentioned in the red and blue AEG-Telefunken pocketbooks of 486 pages, has been measured all the way with full documentation....but only with one or two voltages.
As you pointed out the tube-designers datasheets made by the manufacturer is no longer available. I have gathered several tubes during the last two decades...NOS or NIB and even many used tubes.
It would be very nice to know the exact curves of a "New in box" tube, and at the same time whether the tube-test could show the percentage of useful lifetime remaining in a used tube. Do we have 50-60-70% lifetime left where the tube still meets the specifications?

A lot of questions and I hope to get some of the answers later.

Kim

[Ed_Dinning]

Hi Kim, there is another thread on this site, Synchrodyne was on of the main contributors and that was all to do with valve life. In the components and circuits section I think.

Ed

[leakstereo20]

Originally Posted by Ed_Dinning

Hi Kim, there is another thread on this site, Synchrodyne was on of the main contributors and that was all to do with valve life. In the components and circuits section I think.

Ed

Hi Ed,

Thank you , I found the thread and Synchrodyne. I shall have a closer look.

Kim

[stuarth]

Anyone seen the valve tester on this site http://www.michas-bastelzimmer.info/Units.htm

There's a mini "oscilloscope" there too

Stuart

[leakstereo20]

Originally Posted by stuarth

Anyone seen the valve tester on this site http://www.michas-bastelzimmer.info/Units.htm

There's a mini "oscilloscope" there too

Stuart

Hi Stuart,

This is a very interesting site you found. thank you.

Kim