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Trouble on Zen V9
Trouble on Zen V9
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Old 19th April 2012, 02:03 PM   #1
Billy60300 is offline Billy60300  France
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Location: in a small town called Senlis, north of Paris
Default Trouble on Zen V9

Hi everyone

I am trying to start a Zen V9 and it just won't work.
Here are how things are. I use the NP article 'Zen variation #9'
Q4: Supply is 30 V to start with. Professional power supply, no problem there with a current limit set to 3 amps. VD is 30, VS is about 28V.
Q3: VD is 28v, VS is 26.2V. Replaced ZTX by a BC107, adjusted pinout of ourse, the BC is in fine shape. Shows the regular 0.6V between B and E, C to
Vout is 26.2V and here is the problem: the 25K pot does not have any action, the VG of Q2 remains stuck at a max of 0.7V, whichever position it is set.
For the testing I replaced Q1 by an AMmeter.
No current goes by.
Q2 is blocked, VD as said and VS to GND, VG to 0.7V.

I tested all mosfets and they run fine, it seems that they are OK. I even replaced Q2 by an IRFP044 to compare, o difference.

What is your advice ?

Thanks to all in advance.
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Old 19th April 2012, 05:43 PM   #2
vdi_nenna is offline vdi_nenna  United States
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Hi Billy,

I had an issue with my Zen 9 two weeks ago. I believe, in the end, the problem was a cold solder. A loose resistor near Q5.
Zen 9 - Troubleshoot Bad Channel

If nothing burned, then you are more than half-way there!
Are both channels not functioning? Are they behaving the same?

With your power supply, the Drain voltage at Q2 should be set to close to 14v, set by P1. So, if you are not seeing 14v on the Drain of Q2, check the soldering on Q2 and all components connecting near Q2. Perhaps you should try to replace Q2.

Also, check the voltage across R4 through R6. Article says it should be around .66v to create a 2 amps constant current. What voltage are you seeing across R4-6?
I build, therefore I am.

Last edited by vdi_nenna; 19th April 2012 at 05:49 PM.
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Old 20th April 2012, 01:05 PM   #3
Billy60300 is offline Billy60300  France
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Join Date: Jan 2011
Location: in a small town called Senlis, north of Paris
Only one channel built.
A this pont I am redoing a new PCboard to have all Transistors from the same side.
It will allow me to resolder everything, just in case.
I don't think it is the cause of my roblem since I double checked already the soldering.
I'll let you know how it turns out.
No voltage between both sides of R4-6, coherent withno current flow. The Q2 is blocked.
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Old 22nd April 2012, 12:50 PM   #4
Billy60300 is offline Billy60300  France
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Join Date: Jan 2011
Location: in a small town called Senlis, north of Paris
Hello all and especially Simon.
So, I made a new PCB which is 'better' in IMHO.
here are the results:
1) It is now possible to get easily with the 25k pot the half VCC, just needed to have a stronger VCC: I am now working with 40 Volts. So this part of the problem is solved.
2) the current source still puzzles me: it is impossible to get 2 amps with 0.33 Ohms R4 set. I get only 0.9 A. If I try to lower this one momentarily by paralleling something, the current remains to the 0.9 amps it was !
3) I tried adding a diode in the E circuit of Q5: all the same. there is no tracking of Q5 Vbe.

strangely or not, the whole circuit gets upset (Q3 blocks) if I connect my digital meter around the Q3 gate. When I remove connection, everything gets back but very slowly (due to C4 loading/adjusting I suppose).

So, how to get the Aleph current source to work normally ?

Thanks to all
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