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Simplistic Mosfet HV Shunt Regs
Simplistic Mosfet HV Shunt Regs
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Old 18th September 2019, 07:59 PM   #5981
Tix88 is online now Tix88  Italy
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Hi Salas. I would like to ask you since the power supply box is separate from the preamplifier, I read that the two outputs must be short-circuited to transform it into a classic feed, there are contraindications if I reach the outlet directly with 4 twisted wires and then I start with a plug with 2 wires?
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Old 18th September 2019, 10:58 PM   #5982
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Can you draw what you mean for clarifying?
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Old 21st September 2019, 06:59 PM   #5983
Tix88 is online now Tix88  Italy
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Do you think the two schemes are more functional?
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Old 21st September 2019, 07:22 PM   #5984
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Both are functional, first one is better for less interaction.
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Old 12th October 2019, 03:09 PM   #5985
Embehu is offline Embehu  Viet Nam
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Hi Salas,
Im using your schematic to build a regulator for 90vdc and 80mA. The 3281 pnp trans I replaced with mje350 and the 1k//vr 5k , other one is same. How ever, Im getting stuck. I can’t change the output voltage (130vdc) with the dc electric load (I built it base on Dave on eevblog) at 80mA. Also conect S0 F0 s+ f+
I took some measurements: V 1.8k = 0
Vec of pnp = 0, the other one is 3.5-5.x V
Can you please help me out, I’m just electric hobby not pro
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Old 12th October 2019, 07:50 PM   #5986
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Which one schematic of all? Verify the voltage reference resistor(s) are not too high value for 90V. Verify the constant current you set is higher than the load mA.
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Old 13th October 2019, 12:21 AM   #5987
Embehu is offline Embehu  Viet Nam
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Quote:
Originally Posted by Salas View Post
Which one schematic of all? Verify the voltage reference resistor(s) are not too high value for 90V. Verify the constant current you set is higher than the load mA.
Iím using the hv2 schematic
You mean the two 68k? Can I change to 27k?
For the load, I couldnít change the value more than 0.7V (70mA)

I will try to change 68k, hope it works
Thank you so much!
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Old 13th October 2019, 12:31 AM   #5988
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Even if you made no other mistake and the key JFET is genuine, do lower the 68K resistors when looking for 90V output range anyway. Try whatever logically smaller values you have in hand first.

In post#1 there is a link on how to test the CCS section (DN2540s) in low voltage safe mode. The constant current you set must cover for the load mA and then some. That dialogue continuing until the troubleshooting member had solved an issue in the shunt voltage section. Good hints there.
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Old 13th October 2019, 10:34 AM   #5989
Embehu is offline Embehu  Viet Nam
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Quote:
Originally Posted by Salas View Post
Even if you made no other mistake and the key JFET is genuine, do lower the 68K resistors when looking for 90V output range anyway. Try whatever logically smaller values you have in hand first.

In post#1 there is a link on how to test the CCS section (DN2540s) in low voltage safe mode. The constant current you set must cover for the load mA and then some. That dialogue continuing until the troubleshooting member had solved an issue in the shunt voltage section. Good hints there.
Thank so much for guiding me. I followed your method then I found the Zenner and Jfet are defected.
I changed 68k to 27k
Now it works but still have minor issue because I replaced k117 with j112. Will be fine when I get k117
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Old 13th October 2019, 04:22 PM   #5990
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
What type of minor issue? Watch out for fake K117 in the market. J112 modern batches are usually hot for IDSS thus having too high VGS(OFF) for this circuit. Meanwhile use the lowest IDSS sample you may have.
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