Calling all valve GURUS

[Wakefield Turntables]

I just need a little help. I'm after a modern day valve tester. I'm mainly want to test ECC83's and KT88's as these are the valves I seen to prefer. I'm mainly wanting a simple, cheap(ish) and accurate valve tester. I have no experience in this area or any clue of "brands", so as such don't really know one good tester from another. Any suggestions of brands to avoid/buy would be most welcome. Thanks in advance.


Andy

[SPS]

I'm no help with buying a cheap one, but your more than welcome to use mine..
I live near the humber bridge..

[Mixc]

I just need a little help. I'm after a modern day valve tester. I'm mainly want to test ECC83's and KT88's as these are the valves I seen to prefer. I'm mainly wanting a simple, cheap(ish) and accurate valve tester. I have no experience in this area or any clue of "brands", so as such don't really know one good tester from another. Any suggestions of brands to avoid/buy would be most welcome. Thanks in advance.


Andy

Hi Andy.

I have used one of these ...

https://www.andertons.co.uk/guitar-dept/electric-guitar-amps/electric-guitar-amp-accessories/valves-parts/orange-vt1000-valve-tester

and it worked really well. Allowing to pair match 6550 .
It depends what you need to test.


"
In approximately two minutes, the VT1000 performs an extensive series of tests including:

Heater filament test: Short circuit
Heater filament test: Open circuit
Heater filament test: Tolerance check
Heater cathode insulation: Leakage
Heater cathode insulation: Short Circuit
Tests for heater current abnormalities
Amplification factor
Voltage gain
Power gain
Screen grid test
Mutual conductance test
Dual test for double triodes
Emission
Inter electrode leakage
Inter electrode short circuit
Flash-over (arc detection, high voltage breakdown)
Gas ionisation test
The VT1000 really opens the door to everyone to have an extremely simple, portable, reliable, inexpensive and safe way to test valves.

The VT1000 incorporates patent-pending technology and currently tests the following valves:

EL34/6CA7; EL34L; 6L6; 6V6/6v6GTA; KT66; KT77; KT88; 6550; 5881; EL84/6BQ5; ECC81/12AT7; ECC82/12AU7; ECC83/12AX7; ECC99; 12BH7
"

https://orangeamps.com/products/accessories/amplifier-management/valve-tester/#top

[Wakefield Turntables]

Many thanks Mick, I'd seen this during a bit of research. It's always useful to ask others with more experience. ;)

[Wakefield Turntables]

I'm no help with buying a cheap one, but your more than welcome to use mine..
I live near the humber bridge..

Thanks Steve, that's a very kind offer!

[Jazid]

Others see it differently:

https://www.gearslutz.com/board/so-much-gear-so-little-time/1081915-orange-vt1000-tube-tester-problem.html

I have no experience so don't have an axe to grind but the lack of readings, lack of repeatability, and false positives and negatives suggest it's not close to lab-worthy. I'd save up for a good tester such as an AVO Mk3 or 4, build a pi-tracer or similar, or look for someone else with reliable equipment to do the measurements for you.

Sent from my BLA-L09 using Tapatalk

[Wakefield Turntables]

Others see it differently:

https://www.gearslutz.com/board/so-much-gear-so-little-time/1081915-orange-vt1000-tube-tester-problem.html

I have no experience so don't have an axe to grind but the lack of readings, lack of repeatability, and false positives and negatives suggest it's not close to lab-worthy. I'd save up for a good tester such as an AVO Mk3 or 4, build a pi-tracer or similar, or look for someone else with reliable equipment to do the measurements for you.

Sent from my BLA-L09 using Tapatalk

Thanks James, and that's why I asked for some advice from you guys!

[Mixc]

Others see it differently:

https://www.gearslutz.com/board/so-much-gear-so-little-time/1081915-orange-vt1000-tube-tester-problem.html

I have no experience so don't have an axe to grind but the lack of readings, lack of repeatability, and false positives and negatives suggest it's not close to lab-worthy. I'd save up for a good tester such as an AVO Mk3 or 4, build a pi-tracer or similar, or look for someone else with reliable equipment to do the measurements for you.

Sent from my BLA-L09 using Tapatalk

Hi James
All info helps.

I borrowed the one i used and thought it was excellent. But it doesn't do ECC88 so i didn't get one of my own.
I will try and borrow it again to see if it grades the 6550 the same way as before.
The results were repeatable but you cant test same valve within a ?? time period, It needs to test from cold.
I tested 20 6550 power valves that were supposedly matched when purchased.
After a months burn in i tested, the tester assigns a number (grade) to each valve mine tested between (8 and 11)
i could then match these numbers to create pairs.
It also confirmed the faulty valves i had as faulty.
Nothing is perfect but my experience with the one i used was positive.

Mick

[Mixc]

Hi Andy, what tests do you want to do on the valves?

PS i wouldn't consider myself a valve guru..., just someone with an opinion :)

[Old boy]

I’d echo Jazid’s opinion, invest in a decent Avo, a proper test machine.

[Wakefield Turntables]

Hi Andy, what tests do you want to do on the valves?

PS i wouldn't consider myself a valve guru..., just someone with an opinion :)

The idea was just to purchase a cheap, reliable piece of kit which would provide accurate assessment of the valves health. Ultimately I just something that could accurate grade my valves for future projects, then hopefully enabling me to use the best (healthiest) valves for the job. I understand that only so many tests can be performed upon a valve. I intended to then research each test and it's relevancy. I perform diagnostics on people every day to assess health so I figure I might have a fighting chance of understanding the test values and their relevancy to the valves health (:lol: well that's the logic of a clinician)!!!! Hope you can see my head logic.

[da2222]

The idea was just to purchase a cheap, reliable piece of kit which would provide accurate assessment of the valves health. Ultimately I just something that could accurate grade my valves for future projects, then hopefully enabling me to use the best (healthiest) valves for the job. I understand that only so many tests can be performed upon a valve. I intended to then research each test and it's relevancy. I perform diagnostics on people every day to assess health so I figure I might have a fighting chance of understanding the test values and their relevancy to the valves health (:lol: well that's the logic of a clinician)!!!! Hope you can see my head logic.

Very difficult to do unfortunately...You can find various emissions only types but they only tell part of the story. The AVO CT 160 is very good indeed and will offer mutual conductance and other crucial tests, but yes, it's expensive. For peace of mind it is always good to test the tube in situ in 'real' apparatus after standard testing.

[Mixc]

The idea was just to purchase a cheap, reliable piece of kit which would provide accurate assessment of the valves health. Ultimately I just something that could accurate grade my valves for future projects, then hopefully enabling me to use the best (healthiest) valves for the job. I understand that only so many tests can be performed upon a valve. I intended to then research each test and it's relevancy. I perform diagnostics on people every day to assess health so I figure I might have a fighting chance of understanding the test values and their relevancy to the valves health (:lol: well that's the logic of a clinician)!!!! Hope you can see my head logic.

Some one Pls correct me if im wrong ..

The way i see it..
Each valve gives a specific output for a given input.
If a valve is tested at *?* input it gives an output *?* and can be matched to another valve with similar results.
If a valve operates an input Between *1* and *10* The best way to test at 1 , 2 , 3, etc this gives an output curve.
I think these testers that can do this are expensive.
A power valve (KT88) has a single output.
Whereas a dual triode (ECC83) has 2 outputs.
Dependent on the use or circuit, matching of the valve to itself or to another valve is important.
Some circuits put both left and right channel through one valve and some have a valve for the left and a valve for the right.
My power amp works on push / pull so each half of the wave form is handled by one 6550.

There is a lot to testing and matching valves, so the type of tester required would be down to what tests needed to be performed.

Correctly matched valves are expensive because of the time involved in testing.
I read somewhere that Audio Research have a reject rate of 98% of their purchase valves.

Mick

[Mixc]

Very difficult to do unfortunately...You can find various emissions only types but they only tell part of the story. The AVO CT 160 is very good indeed and will offer mutual conductance and other crucial tests, but yes, it's expensive. For peace of mind it is always good to test the tube in situ in 'real' apparatus after standard testing.

How would you test in situ ?

Measure the output or measure at various points in the circuit?

[Wakefield Turntables]

Some one Pls correct me if im wrong ..

The way i see it..
Each valve gives a specific output for a given input.
If a valve is tested at *?* input it gives an output *?* and can be matched to another valve with similar results.
If a valve operates an input Between *1* and *10* The best way to test at 1 , 2 , 3, etc this gives an output curve.
I think these testers that can do this are expensive.
A power valve (KT88) has a single output.
Whereas a dual triode (ECC83) has 2 outputs.
Dependent on the use or circuit, matching of the valve to itself or to another valve is important.
Some circuits put both left and right channel through one valve and some have a valve for the left and a valve for the right.
My power amp works on push / pull so each half of the wave form is handled by one 6550.

There is a lot to testing and matching valves, so the type of tester required would be down to what tests needed to be performed.

Correctly matched valves are expensive because of the time involved in testing.
I read somewhere that Audio Research have a reject rate of 98% of their purchase valves.

Mick

Interesting post Mick, I'm sure your perfectly correct, just goes there's more to this valve testing thingy than meets the eye.

[Jazid]

Hi Andy,

As a clinician you appreciate the relevance of separate and complementary tests to ascertain the DUT's (PUT's?) condition. The trouble with a 'one size fits all' approach is the shortfall of usable information. For example do you need to know the emmissions of the valve? Then for starters you really need to know what current it conducts at a specified anode and grid voltage, ideally at several different combinations to construct a chart to compare to those that the manufacturer published. You may also need to know the transconductance in mA/V, again at the specified point as a minimum standard and ideally charts to see if it meets spec. Impossible with a good, ok, bad test. The trouble is valves are inherently variable and often one will have slightly high emmissions but conversely exhibit slightly low transconductance or vice versa, and this can be normal and within manufacturer's tolerance. However without knowing the measurements and their respective conditions one cannot judge whether one valve is equivalent to another which may also be within tolerance but have rather different measured specs. When matching valves this becomes a significant issue as one presumes all valves sold new should be within spec, but not necessarily adequately matched for the purposes of the circuit they might end up in - one reason for the introduction of SQ and uprated types, and selection and marking of 'instrumentation grade' valves by manufacturers of lab equipment.

As an example for power valves in manual bias circuits you normally want close matching emmissions at a particular grid voltage. For push pull self bias circuits you may however prefer valves with tightly matched transconductance curves. In pre-amps a double triode may need matching sections or it may not depending on what the two sections are doing. If they are amplifying the same stage in two channels they will need to be matched, if they are amplifying different stages then balance between the equivalent sections of different valves may be more important than between the two sections of each valve.

Similarly it is good to know that the heater:cathode insulation is high in a valve, and in some circuits imperative that it meets valve design spec, but in others it is not so important; If you are using venerable or uncommon valves then it is prudent to use those which are strong but which due to age have less than brilliant insulation in circuits where the heater:cathode voltage is low, rather than discard them just because they won't work well in a circuit where the design h:c voltage is high.

Likewise testing a valve's emmissions with a high voltage pulse will 'work' and this will be how the Orange tester operates I suspect since it seems to use a wallwart SMPS. It may even excite a flashover if the valve is on the edge. But running a valve at design limit voltage and current (or beyond) for a length of time is a more exacting test, and if there is a potential failure mode eg. hotspots on the anode then in such a test this is more likely to become evident. The ability of the valve to sustain emmissions can also be tested - an important consideration if the plate or cathode are slightly poisoned or there is some slight gas to 'burn off' from eg. valves which haven't been used for a long time.

So I'd say if you are looking to play with your thermionic friends in due course then a decent tester is a worthwhile investment. There is a new-ish tester but I cannot recall the name (maybe a bit DIY but not so much as the pi-tracer). It looked good when I nosed around, think a question in DIY section will elicit the answer. There is also the expensive but impressive Amplitrex 1000 as well if you need to get yourself a Christmas pressy, or a properly fettled Mk4 AVO, Neuberger, or a Kalibr L3-3
*edit* or indeed AVO CT160 as Drew mentions, or VCM163...

[da2222]

How would you test in situ ?

Measure the output or measure at various points in the circuit?

No, I simply mean after testing subject the the tube to 'real' conditions ie an amp or intended device...