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Zen Variation 9
Zen Variation 9
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Old 8th January 2018, 10:55 AM   #1
wg79 is offline wg79  Poland
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Default Zen Variation 9

Hello.
I am new here. I joined because I have a 'little' problem with my Zen v9. I have made Zen v4 and it sounds well but I found LU1014 and I wanted to do v9. I know it's an old contruction but it should sound much better. I made PCB according to fig.8 of this article Zen Variations 9 | Pass DIY but I can't set any current by setting P1.
I don't understand a way of control Q1. I have 44V instead of about 23V on a drain of Q2. It means there is no current. I can set 3V on drain of Q1 but there is still no current. Q1 is stuck. But it's connected to ground by R17+R7. Lu1014 is a N-channel transistor so it is switched off by grounding. I made a test schema according to fig 10 and if its gate was connected to ground Q1 didn't conduct. It conducted only if I got + to gate.
So if you were so pleasant and patient please explain it to me.
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Old 8th January 2018, 11:15 AM   #2
Zen Mod is offline Zen Mod  Serbia
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Zen Variation 9
LU1014 is JFet , normally on part , so you need negative at gate to shut it off

you probably have fake one , if you need positive voltage at gate to conduct

if you did something , and it doesn't conduct with article - problem is at your side - either dud part or implementation
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Old 8th January 2018, 11:30 AM   #3
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by wg79 View Post
............. Lu1014 is a N-channel transistor so it is switched off by grounding.
Lu1014 is a depletion mode FET
Depletion and enhancement modes - Wikipedia
Quote:
I made a test schema according to fig 10 and if its gate was connected to ground Q1 didn't conduct. It conducted only if I got + to gate.
So if you were so pleasant and patient please explain it to me.
you are describing an Enhancement mode FET.
Looks like you have bought fakes or you are not testing them correctly.
Vertical mosFETs are available very cheaply. All the cheap ones are enhancement mode. These are what get used to make fakes of the more expensive Laterals and jFETs.
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Last edited by AndrewT; 8th January 2018 at 11:32 AM.
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Old 8th January 2018, 11:30 AM   #4
wg79 is offline wg79  Poland
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Thank you for your fast reply.
I suppose they are fake (China). I checked PCB twice and I found a mistake before. C1 capacitor was mounted inversely and it conducted. Then I was able to set the current because I give + to gate of Q1. But R7 resistor was burning.
Where can I buy real LU1014.
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Old 8th January 2018, 11:36 AM   #5
Zen Mod is offline Zen Mod  Serbia
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Zen Variation 9
either here or here

as far as I know , those are genuine
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Old 8th January 2018, 12:48 PM   #6
wg79 is offline wg79  Poland
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Thank you again.
There is a saying in Poland - 'cheap meat is eaten by dogs' and it is still actual (my example).
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Old 8th January 2018, 05:41 PM   #7
Nelson Pass is offline Nelson Pass  United States
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Zen Variation 9
If someone with a U.S. address wants to organize distribution, I am happy to
donate a quantity of these Jfets for DIY. Match them yourself....
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Old 9th January 2018, 05:50 AM   #8
wg79 is offline wg79  Poland
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Quote:
If someone with a U.S. address wants to organize distribution...
It sounds great but there is IF. Anyway thank you for it.
All of you helped me a lot. I didn't realize that quite cheap elements and not so common might be fake.
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Old 9th January 2018, 02:18 PM   #9
woody is offline woody
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I also picked up a few fake ones from ebay.
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Old 9th January 2018, 02:51 PM   #10
Dennis Hui is offline Dennis Hui  Canada
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Zen Variation 9
That's unfortunate.

I had heard of folks getting parts that appeared used but were otherwise OK.

I would be more than happy to volunteer to measure and distribute parts, but
alas I'm in the Great White North.
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