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Old 17th March 2013, 01:48 PM   #1
lhgin is offline lhgin  Malaysia
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Cool EL152 maximum operating settings?

Hi guys,

Need some help on EL152 German datasheet. The EL152 has a 40W anode/plate dissipation. It is strange that (if I translate it correctly), on page 10, when triode-connected, the steady state current Iao is only 30mA?

Refer datasheet below:
http://www.mif.pg.gda.pl/homepages/f...18/e/EL152.pdf

If it is a 40W plate, when triode connected with the anode voltage at 400V, by right the maximum anode current should be able to go up to 100mA.

I tried to refer else, for example, in page 9 of datasheet, in pentode mode, it states 300V on anode/plate but the Ia is left empty. Issh...

I'm scratching my head all over. Hope the gurus here could give me some advice or explanation on the above.

Thanks!
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Old 17th March 2013, 02:29 PM   #2
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These are TV pentodes and the g2 voltage is always considerably lower than the plate voltage. This dissipation on the g2 is what restricts the steady state plate current to just 30mA.

Shoog
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Old 17th March 2013, 03:48 PM   #3
Ketje is offline Ketje  Belgium
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Indeed somewhat curious data,you don't expect from the German "grundlichkeit".
I supose you may go for 400V/60mA ,don't think you get even 5W out.
Why 60mA? Pg2=5Wmax that is 12.5mA at 400V.Safeside say 10mA.The other data indicate that Ig2 is aprox.20% of Ia.Gives Ia=50mA+10mA(g2) total of 60mA.
Mona
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Old 17th March 2013, 04:12 PM   #4
es345 is offline es345  Germany
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I assume that you want to use the EL152 in SE Triode mode. The EL152 as well the GU50 is basically a copy of the RF/AF power pentode LS50. Here are some data for that tube in SE Triode mode. You will find the output power for 250V and 400V as a parameter of the OT impedance. In that diagram Iad is the plate current at full power.
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File Type: jpg LS50 SE diagram.jpg (76.0 KB, 186 views)
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Old 18th March 2013, 12:51 PM   #5
lhgin is offline lhgin  Malaysia
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Shoog/Ketje,

Man... I thought with 40W Pa, I can get something decent out of it. Looks like it's a bummer. I need to research more on how to dig out more power from this tube. I have not seen any successful implementation of this tube in the internet yet.

es345,

Thanks! Do you have any recommendations on the operating point for EL152?

Thanks guys!
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Old 18th March 2013, 12:55 PM   #6
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You could try a pentode implementation with plate to grid feedback. This should allow you to respect the g2 voltage whilst running at your higher plate current. It should allow you to produce something very similar or better than Triode performance with lower output impedance than a straight triode configuration.

If you do - make certain to use a pentode driver.

Also it seems that a GU50 schematic might easily be adapted.

Shoog

Last edited by Shoog; 18th March 2013 at 01:02 PM.
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Old 19th March 2013, 03:10 PM   #7
lhgin is offline lhgin  Malaysia
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Thanks Shoog.

Let me go dig more GU50 schematic. Seems to be plenty on the net.
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Old 19th March 2013, 05:02 PM   #8
es345 is offline es345  Germany
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Quote:
Originally Posted by lhgin View Post
Thanks! Do you have any recommendations on the operating point for EL152?
Well, I personally don't use them in SE Mode but in PPP. My 6xGu50 bass amp is working in class B producing about 400W Output (Raa 2KOhm)
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Old 19th March 2013, 09:16 PM   #9
wfmali is offline wfmali  Europe
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I had a similar concern with a GU50 triode strapped, but more related to how much voltage the g2 could take (specified with 250V max). I performed some measurements at 500V anode/g2 showing that g2 current in triode mode is basically negligible - g2 dissipation is definetly not an issue. This seems logical considering the significantly larger anode surface that simply attracts way more electrons then a grid-wire at the same potential. G2 is usually "at risk" when it has to take over the current of the anode, e.g. in UL or penthode operation where the anode voltage can swing much lower then g2 potential. But since both anode and g2 are tied together, they share the same potential at any time.
Bottom line, here it works with 500V and 60mA - might be luck, don't know... One thing to notice thought is that Rg1 is supposed to be low for LS/GU50/EL152. Specification talks 25k'ish which requires a beefy driver. Maybe the 30mA spec limit is in place to prevent from thermal runaway issues (which I have not seen so far)?

Marcus
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Old 19th March 2013, 10:39 PM   #10
es345 is offline es345  Germany
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here is an LS50 (EL152/GU50) SE Pentode curve.
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File Type: jpg LS50 SE diagram pentode.jpg (59.0 KB, 125 views)
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