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Simplistic Mosfet HV Shunt Regs
Simplistic Mosfet HV Shunt Regs
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Old Yesterday, 09:19 AM   #6021
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Sounds pretty catastrophic. Maybe an insulation issue or a PCB issue? An arc? I don't know this green PCB you showed.
In your shoes I would either follow the whole troubleshooting procedure link going down to last components like Zeners and trimmer, after inspecting and cleaning the board thoroughly, or simply restart and build new with a clean slate but with fuses on its input and output this time. Slow blow ones of comparable value to the CC setting.
Also by using a fat Schottky diode instead of the Zener (the one near the JFET). If planing to transplant some parts, trust only those that will measure OK off board on their own with DMM and transistor tester.
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Old Yesterday, 02:42 PM   #6022
bigpandahk is offline bigpandahk  Hong Kong
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I measured the voltage at each stage again and found that when input goes higher than 230V, the voltage at C1 dropped to lower than 20V. So it should be Q1, Q2 have problem. As I don't have any more spares, need to order some and try again later.
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Old Yesterday, 03:09 PM   #6023
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
There are some IXYS HV DMOS options too. MJE350 can substitute any dead Q4 Q5 also if available locally. Lower spec option but good enough for proof testing.
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Old Yesterday, 03:17 PM   #6024
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
P.S. Also try one of those transistor testers with the ZIF socket and little LCD screen found everywhere online. They are good enough for recognizing semiconductor types, sorting out working or dead ones, comparing some parameters etc. They are very cheap and can be helpful.
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Old Today, 02:07 PM   #6025
bigpandahk is offline bigpandahk  Hong Kong
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All semiconductors ordered and will be delivered tomorrow. As per your recommendation, I bought a Chinese transistor tester at only $8.
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Old Today, 02:20 PM   #6026
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
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