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Anyone out there with a KT150?
Anyone out there with a KT150?
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Old 4th February 2017, 04:26 PM   #1
wfmali is offline wfmali  Europe
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Default Anyone out there with a KT150?

Hello, I am running SE-monos with KT150@50W anode dissipation. What I do see is a dull red glow of the anode in the pin 1 area, the attached picture shows it quite nicely. I do own 4 KT150s, they all show the same behaviour, in both amps. KT120s with the same dissipation settings, however, do not show any signs of anode glow. Did anybody owning KT150s notice a similar behaviour? Would not really like to challenge mine with the rated anode dissipation of 70W.... Thought I bought them from a reliable source, do who knows ? Or this is a KT150 feature, not a failure - they accumulated at least ~150h so far quite happily... Any hint is very much appreciated!

Marcus
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Old 7th February 2017, 01:15 PM   #2
ulibub is offline ulibub  France
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Hello Marcus,

I built a KT150 PP-Amp during winter 2014/15, which has obtained in the meantime its 2nd set of power tubes - the first set had about 4000 hrs. The tubes are running with up to 600V plate voltage at about 80 - 85 mA current, measured at the cathode, so dissipation is also in the 50W-area.

I never observed "red cheeks" at this point - but yours appears to me also quite faint... But I must say, that I wasn't very satisfied with the quality of these tubes - with continuing age they started to get more and more unstable (running away to heavy red plating from time to time, but after switching off and cooling down they were ok again for quite a long time...), although grid resistance is 22 kOhms - far away from the 47 kOhms maximum. So I added an automatic working point control and regulation to keep them in safe conditions. Since then I had no more problems.

Also, the Getters were quickly fading, and with continuing fading, the instabilities increased. Seems as if the metal parts were not sufficiently degassed during production.

This is in a strong contrast to an amp with the 211-triodes (Psvane 211 MK II) I built last winter - these tubes have also in the meantime a lot of hours (> 2000) and are still looking like new...

The new set of KT150s appears to me as of a better quality. They haven't so many hours so far, but the fading of the Getters seems to be slower than in the former set - maybe their production quality increased with time?

all the best

Uli
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Old 7th February 2017, 02:38 PM   #3
artosalo is offline artosalo  Finland
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Has anybody wondered why the manufacturer has not published reasonable specifications ?
These are not sufficient at all: http://www.newsensor.com/pdf/tungsol/kt150-tungsol.pdf
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Old 7th February 2017, 07:46 PM   #4
wfmali is offline wfmali  Europe
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yep, time of detailed information is long gone...
@Uli: nice assemble for some serious power. Do you phase-split using the input-transformer? Like that a lot...
I use my 150s with a CCS, and after some serious warm up time it is dead quite and stable. Getters are fine as well...just don't like that for my KTs 50W is about it, it is like running the final at 100%, which was never the intention...
Marcus
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Old 8th February 2017, 11:21 AM   #5
srb02 is offline srb02  United States
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Yup, got one, and it does the same thing. In pic, it's KT120, but 150's also do it.

PM coming.

Stu
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Old 8th February 2017, 11:47 AM   #6
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Over dissipation with these valves will heat the anodes up too far and you will lose power output. Increase the negative bias on the grid to just before the anode glows. That may make them last a bit longer.
Chinese valves, don't you just love them.
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Old 8th February 2017, 01:02 PM   #7
Kay Pirinha is offline Kay Pirinha  Germany
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Quote:
Originally Posted by JonSnell Electronic View Post
Chinese valves, don't you just love them.
Yupp ,especially their suppository-like appearance *bigfatgrin*!

From a commercial tube that is not dedicated for transmitting services I do not expect any glow on it's plate, unless the dissipation rating given in the datasheets are exceeded. Otherwise I'd say the tube itself, or the datasheet, are fake.

Over several thousands of years, longer than any other nation, the Chinese have gathered great experience and knowledge in making fire crackers. Obviously they continue to apply those in making tubes.

Best regards!
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Old 8th February 2017, 01:20 PM   #8
ulibub is offline ulibub  France
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Quote:
Originally Posted by wfmali View Post
yep, time of detailed information is long gone...
@Uli: nice assemble for some serious power. Do you phase-split using the input-transformer? Like that a lot...
I use my 150s with a CCS, and after some serious warm up time it is dead quite and stable. Getters are fine as well...just don't like that for my KTs 50W is about it, it is like running the final at 100%, which was never the intention...
Marcus
Hi Marcus,

yes, this amp is a real "steam-engine" with an enormous power. I use the input transformer (Sowter) also for phase splitting. Expensive, but for avoiding ground loops indispensable. Input stage and driver are a PCL84, the video driver of old-time black & white TV-sets...

In general, I often have observed in these quite high-mu beam-power tetrodes an uneven density of the electron beams on both sides - often, the beam on one side is much stronger than on the other, so that most of the dissipation is generated at one side. So this side gets much hotter than the opposite side, which quickly leads to one-sided red plating even if the maximum permissible overall current is far from being reached. I think this comes from a not 100% even alignment of the grids in the tube - also a quality issue...

all the best
Uli
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Old 8th February 2017, 01:48 PM   #9
MelB is offline MelB  Canada
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Quote:
Originally Posted by JonSnell Electronic View Post
Over dissipation with these valves will heat the anodes up too far and you will lose power output. Increase the negative bias on the grid to just before the anode glows. That may make them last a bit longer.
Chinese valves, don't you just love them.
Aren't the "KT" tubes made in Russia? My KT120's all have Made in Russia printed on the base.
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Old 8th February 2017, 02:01 PM   #10
srb02 is offline srb02  United States
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both my 120's and 150's do say russia.

stu
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