| volle |
Hello I'm a new "Zendiy". I hope I will show you my realization soon...
I meet a problem maybe someone met too.
During the test of the two channels, I replaced the 50v unregulated by a power supply and the two worked very well. When I tryed with the 2x18v transformer, I have a problem on a channel I can't explain. R4 has no action on the circuit. The voltage across R0/R1 is about 0,75v and I can't adjust it. I havn't this problem on the other channel. Q4 seems to work well and I can observ all the voltage showed on the schematic (no exactly the same value due to R4).
I don't understand what could be the cause of this behavior. Moreover there are no difference between the two channel circuits.
Thanks for your help and happy new year :D
Vianney |
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| tomchaoda |
Which version of Zen are you referring to?
Thomas |
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| volle |
Hoops!
It's the Penultimate Zen (Part4).
Thanks. :D |
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| joensd |
Do you have about 22V at the drain of Q1?
Are you sure the pot´s ok?
Pop another one in if you have one spare or better measure it.
Cheers
Jens |
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| tomchaoda |
Do this one step at a time. What I will do first:
1. Make sure the 2X18V is in series, not parallel.
2. Check to see if the output after the bridge rectifier and the 25000uf cap is +50V.
Once this is certain, then you can check the rest of your main board.
Thomas |
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| volle |
I tested my board as you said. The pot is still ok.
I can observ about 47V after the cap (I have only 22000uf) ; and 40v at the source of Q5.
On the " good " channel, I have 26,8v at the drain of Q1 when there is 0,66v across R0 and R1.
As N.Pass said : " Adjust R0 so that the drain voltage of Q1 is 1/2 the regulated voltage plus about 2 volts ".Thus I need 22V. So I will adjust R0… as soon as possible.
On the channel wich doesn’t work , I check the drain of Q1.
Effectively there is a problem, I have 3,3v whatever R4…. I see about 4v between the gate and the source of Q2 but 0V between the gate and the source of Q1.
Thanks for your help. :)
Vianney |
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| joensd |
If you have both resistors R0&R1 installed and measure 0.75V you should have a bias of 2.3A which doesn´t sound too bad so far.
The drain of Q1 is a big problem. Of course the whole bias circuitry doesn´t work then.
My first guess would be you touched the mosfet in a kind of loaded moment and it has gone to semiconductor heaven.:angel:
Did you measure the mosfet?
It probably has a short.
You can use this article to test the mosfet or your multimeter.
If this is not the case you probably have a short in your wiring somewhere but I don´t think so.
Good luck
Cheers
Jens |
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