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Old 22nd November 2011, 12:12 PM   #6991
RCruz is offline RCruz  Switzerland
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I always keep it between 7 and 10V
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Old 22nd November 2011, 12:22 PM   #6992
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BiB & I suppose the others regs. too:
Voltage drop across regulator: Get a transformer that for DC gives you at least 5V extra from your target voltage. 7-10V is better against mains fluctuations, transformer regulation with high current etc.
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Old 22nd November 2011, 12:25 PM   #6993
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Hi Merlin

Can you please post a layout of your V12R ?
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Old 22nd November 2011, 12:30 PM   #6994
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Quote:
Originally Posted by RCruz View Post
It works ok with MF or CF but I keep having startup issues with some of my builds.

I found that there is an inductive interaction that sometimes happens, so the shunt only starts if I touch the connection between R2 and Q2.

It is not common and I already built 14 V12R without any issues. Once it happens I need to redo R2 placement until I get it working perfectly.
Correction

The stubborn shunt fires when I touch R3 on Q3 side (Not R2 Q2 as I stated before)

I usually solve this issue by moving R3 and not R2.
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Last edited by RCruz; 22nd November 2011 at 12:37 PM.
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Old 22nd November 2011, 12:32 PM   #6995
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Hello Ricardo,

The schematic V1.2R that I use.
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File Type: jpg Salas shunt V1.2R.jpg (171.1 KB, 198 views)
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Old 22nd November 2011, 12:43 PM   #6996
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Thank you... Now can you please post the layout or pictures of the shunt ?

I would like to compare the positions of R3 and Q3 in your shunts with mine
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Old 22nd November 2011, 12:51 PM   #6997
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Quote:
Originally Posted by RCruz View Post
shunt fires when I touch R3 on Q3 side
I think what is happening is that your finger is injecting a small pulse to turn on the CCS FET.

A resistor + Zener across DS of the CCS FET may solve this turn on fault.

Maybe try 12V or 15V Zener and a 1k or 2k resistor.
At start up when Vout = 0Vdc and Vin = 52Vdc, with the FET OFF, the Zener will pass 18.5 to 40mA. A couple of mA will turn ON the cascode by developing a LED voltage and the remainder of that start up current starts to charge up capacitances downstream of the CCS.
Once the FET turns ON, the Vout will rise from 2 or 3Vdc to 42Vdc.
The Zener current should now be zero mA and the circuit should work normally.
Probably not the best way to ensure reliable start up. Can someone see a better way?

Will this R+Z be completely innocuous, once the CCS has established correct current?
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Last edited by AndrewT; 22nd November 2011 at 01:01 PM.
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Old 22nd November 2011, 02:12 PM   #6998
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Quote:
Originally Posted by RCruz View Post
Thank you... Now can you please post the layout or pictures of the shunt ?

I would like to compare the positions of R3 and Q3 in your shunts with mine
Pic
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File Type: jpg DSC00051.jpg (853.5 KB, 188 views)
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Old 22nd November 2011, 02:51 PM   #6999
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Quote:
Originally Posted by AndrewT View Post
I think what is happening is that your finger is injecting a small pulse to turn on the CCS FET.

A resistor + Zener across DS of the CCS FET may solve this turn on fault.

Maybe try 12V or 15V Zener and a 1k or 2k resistor.
At start up when Vout = 0Vdc and Vin = 52Vdc, with the FET OFF, the Zener will pass 18.5 to 40mA. A couple of mA will turn ON the cascode by developing a LED voltage and the remainder of that start up current starts to charge up capacitances downstream of the CCS.
Once the FET turns ON, the Vout will rise from 2 or 3Vdc to 42Vdc.
The Zener current should now be zero mA and the circuit should work normally.
Probably not the best way to ensure reliable start up. Can someone see a better way?

Will this R+Z be completely innocuous, once the CCS has established correct current?
Hi Andrew

It seems reasonable and logical.
what would be orientation of the zener ?
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Last edited by RCruz; 22nd November 2011 at 03:03 PM.
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Old 22nd November 2011, 02:52 PM   #7000
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by merlin el mago View Post
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Thank you so much Merlin

Do you have resistors under the board ?
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