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Old 6th Sep 2017, 12:31 pm   #1
andski1
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Default VCM 163 Valve data for 6H30pi & KT 150/KT 120

Hi guys,
wonder if anyone could help with data and pin-out for those three tubes,
is it actually possible to test power tubes like KT 150 & KT 120 on VCM 163?
My audio gear is Audio Research which uses exclusively 6H30, KT 120 and KT 150.
Would this be correct for 6H30 pi:
851 238 410 0000 00
VF 6.3V
Vg1 1.2V
Va 80V

Many thanks in advance,
Andrew
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Old 6th Sep 2017, 1:47 pm   #2
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Default Re: VCM 163 Valve data for 6H30pi & KT 150/KT 120

The quick answer is No, not entirely.

The AVO VCMs (all versions) were made to test general purpose receiver valves and power valves of modest power. They do not have beefy enough power supplies to properly test high power devices like KT66 and KT88. The voltages don't go high enough , nor do the currents they can handle.

So, in the AVO data book there are settings for testing higher power valves under reduced voltage and current conditions so that you can at least spot obvious duds and can have a basic stab at matching pairs. What these tests don't do is give you any guarantee that the device isn't going to exhibit problems under the full voltages and currents they can be used at.

Audio and guitar people are prepared to pay a lot of money for these testers, but unfortunately their sort of valves are exactly the ones they don't test well. This sort of negates the benefit of all those valves offered for sale as "AVO tested"

When you are testing powerful valves, even under the cut-down conditions in the databook, be careful to limit the on time because this can damage the transformers in the VCM.

David
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Old 6th Sep 2017, 4:08 pm   #3
Boater Sam
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Default Re: VCM 163 Valve data for 6H30pi & KT 150/KT 120

The best power valve tester is :----------------------------
A power amp!
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Old 6th Sep 2017, 9:51 pm   #4
frankmcvey
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Default Re: VCM 163 Valve data for 6H30pi & KT 150/KT 120

Hi, Andy,

I tested a number of 6H30pi recently for a friend; beautiful valves - double triodes and a lot more linear than our similarish ECC8*s. I used a DC test setup and basically replicated the valve data Ia/Vg characteristics. Data and pinout here.

I have no experience of the KT120s and 150s other than by reading about them. What a beast the 150 is! As David noted above, testing one of these on a valve tester would be of limited value, since you wouldn't come close to replicating its normal working conditions. Hell, the heater alone pulls 2 amps!

If I were in your position, I'd be looking at using a simple dc test setup for that as well, but you'd have the added complication of having to arrange a screen supply for the beam plates as well as your variable anode HT (say 100V - 500V DC pos), a negative variable supply for your control grid (-5 vdc to -25vdc) and a 6.3 v ac supply @2A for your heaters. You'd also need 4 meters to monitor Vg, Va, Vs and Ia.

Data and pinout for the KT150 is here.

Good luck with it!

Cheers,

Frank

Last edited by frankmcvey; 6th Sep 2017 at 10:00 pm.
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Old 10th Sep 2017, 11:36 am   #5
andski1
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Default Re: VCM 163 Valve data for 6H30pi & KT 150/KT 120

Thank you Radio Wrangler and frankmcvey for your input, I agree VCM163 is great but just not build to handle larger power tubes.
I think Amplitrex AT 1000 maybe better choice for that ? By the way any of you had experience with Amplitrex?
Cheers,
Andrew
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Old 10th Sep 2017, 1:53 pm   #6
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Default Re: VCM 163 Valve data for 6H30pi & KT 150/KT 120

If I need to test something powerful, I usually build a test rig specific to that device (I design 300W 1GHz transmitters for a living) I have a Taylor 45D valve tester for quick checks on mundane types if I'm working on one of my old valved radios. Power valves are easily checked in their intended circuit.

We get a steady flow of unfortunate individuals visiting this forum who are interested in valve guitar amplifiers (occasionally hifi) and have stumped up an awful lot of money for one of the later AVO VCMs under the assumption that at those prices they must be the best and ought to be able to do anything. They then try to use the valve tester to burn new power valves in. The outcome is a VCM with destroyed transformers. Even at the reduced operating conditions in the handbook the machines are only safe for a quick check.

We also get people who haven't been shown how to operate one carefully and they run a test with the Ia scale far too low to start with, and ruin their meter movement coil. The instruction books don't impress on the user just how fragile these instruments can be.

Meter movements and transformers for these things are pretty much unobtainable without the rest of an expensive valve tester wrapped around them, so these people are rather saddened to put it mildly.

They were good tools in a radio/tv shop to check valves brought in. The repair staff just substituted new bottles for a much faster check. They were OK in the development departments of equipment manufacturers for the occasional check. There are movies on like of tours round Mullard's main factory in Blackburn and you may be staggered at how many Avo or other make testers you don't see!

It's a case of horses for courses. Without the hype, a VCM might be worth £100 or so for what it can actually do. THey're nice looking bits of engineering in their own right but they aren't tickets to audio nirvana, nor will they ensure fame and fortune for a guitarist.

It's too easy to assume that things are designed to make sure no combination of controls will result in damage. But this can be wrong. Not even million pound cars will stop someone steering into a wall.

David
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Old 11th Sep 2017, 10:50 am   #7
andski1
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Default Re: VCM 163 Valve data for 6H30pi & KT 150/KT 120

Quote:
We get a steady flow of unfortunate individuals visiting this forum who are interested in valve guitar amplifiers (occasionally hifi) and have stumped up an awful lot of money for one of the later AVO VCMs under the assumption that at those prices they must be the best and ought to be able to do anything. They then try to use the valve tester to burn new power valves in. The outcome is a VCM with destroyed transformers. Even at the reduced operating conditions in the handbook the machines are only safe for a quick check.

We also get people who haven't been shown how to operate one carefully and they run a test with the Ia scale far too low to start with, and ruin their meter movement coil. The instruction books don't impress on the user just how fragile these instruments can be.

Meter movements and transformers for these things are pretty much unobtainable without the rest of an expensive valve tester wrapped around them, so these people are rather saddened to put it mildly.
You pretty quick with your assumptions and conclusions "Radio Wrangler " yet you don't know anything about me, I thought this forum was open to anyone who share passion for old electronics but maybe I was wrong

Last edited by andski1; 11th Sep 2017 at 11:17 am.
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Old 11th Sep 2017, 11:52 am   #8
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Default Re: VCM 163 Valve data for 6H30pi & KT 150/KT 120

I was trying to write a simple warning. If you are going to test those sorts of valves with an AVO valve tester, you are going into territory where a number of people have damaged their VCMs beyond feasible repair. You haven't spoken about what your interests and intents are, so I haven't a clue about your capabilities, so I wrote what was intended as a general warning. We have had several people who have tried to test or burn in high power valves and have destroyed AVO VCMs that they't paid a lot of money for.

This really is a helpful forum and many of us just wished we'd been able to give a bit of warning to those people before things went wrong. Unless someone's experience and capabilities are known, warnings about possible damage to equipment and risks to life and limb are intended to help those who need them, not to offend those who don't.

David
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Old 11th Sep 2017, 11:58 am   #9
John Caswell
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Default Re: VCM 163 Valve data for 6H30pi & KT 150/KT 120

Hi Andrew
I feel that you are being rather harsh criticising Radio Wrangler.
Speaking from much bitter experience on the forums that I belong to, many people join because they have, no idea of electronics, what they are doing, and have "changed all the capacitors because I have read that is the thing to do"
I have certainly had my share of this and the other favourite with radios is "I have done all the screws up "cos they were loose" - complete realignment necessary.
Like RW I have been doing this for many years and "think" I know what I'm doing but I'm still learning

John
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Old 11th Sep 2017, 12:53 pm   #10
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Default Re: VCM 163 Valve data for 6H30pi & KT 150/KT 120

Andrew,

Nothing personal or judgemental was intended in David (RW)'s post- it was simply a wry reflection on a trend that many of us have noticed over the years where posts by new or relatively new members that combine "AVO valve tester" and "audio power valve" tend to ring alarm bells for the sake of the tester's longevity and the owner's wallet. I, and many others, tend to agree with Boater Sam's comment about the intended circuit being the best tester and especially with power valves- it's difficult to replicate the conditions of anode volts, cathode current, peak emission, grid and anode voltage swing, element and bulb heating....etc.... without a bespoke test jig and by time the jig has been made, it's nearly that amplifier anyway. A tester is useful as a duffer/maybe decider but I certainly wouldn't spend lots of money on a NOS or "good, used" power valve on the basis of what a restricted capability, likely uncalibrated, possibly abused, half-century or older workshop device said.

As well as folk who seem in danger of damaging their expensively acquired test gear through misguided/ill-informed "burning in" posts in other forums, there are also those new members who pop up to ask if anyone "just happen" to have ECC8x, U52s, germanium audio transistors, Mullard mustards.... getting in the way that they'd like to pass on. All this makes forum members wary and guarded about vintage audio newbies in particular- most are genuine and interested, but a few are brazen panhandlers, so it can make folk here defensive.

No offence intended,

Colin
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