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Simplistic Mosfet HV Shunt Regs
Simplistic Mosfet HV Shunt Regs
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Old 30th December 2011, 04:09 PM   #2291
merlin el mago is offline merlin el mago
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Is R3 56K 5W? Measure Ohm across it with the reg off.
I did yesterday but I desolder again & read.
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Old 30th December 2011, 04:14 PM   #2292
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
What voltage you can read across it, when the circuit is running? It must be Vin-3xLeds(~Vin-6V).
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Old 30th December 2011, 04:16 PM   #2293
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R3 55K6
R4 119K5
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Old 30th December 2011, 04:19 PM   #2294
merlin el mago is offline merlin el mago
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Originally Posted by Salas View Post
What voltage you can read across it, when the circuit is running? It must be Vin-3xLeds(~Vin-6V).
Across R3 56K?

With 15K dummy load or without dummy load?
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Old 30th December 2011, 04:20 PM   #2295
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Quote:
Originally Posted by merlin el mago View Post
R3 55K6
R4 119K5
They look good. Is that black R1 OK? Can you put a simple metal film with short legs in its place? Did you check there is no continuity between fins and Mosfet tabs?
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Old 30th December 2011, 04:25 PM   #2296
Salas is offline Salas  Greece
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Simplistic Mosfet HV Shunt Regs
Quote:
Originally Posted by merlin el mago View Post
Across R3 56K?

With 15K dummy load or without dummy load?
Yes. But do the continuity and R1 checks before you fire it up.

The dummy load is to take pressure off the output sink and to evaluate heat near operating conditions in application. Since the voltages are high and the dissipation goes easily up, its good to have for heat share and to evaluate R1 so there is just enough extra mA for the reg to work fine above load need, and no heroic sinks. Usually +20-25mA. We use Ohm's law for a dummy near our real load need. So its helpful to have it there.
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Old 30th December 2011, 04:31 PM   #2297
merlin el mago is offline merlin el mago
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I changed R1 for a new one 56R but LEDs still don't lit, can I fire up to measure voltage across R3?
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Old 30th December 2011, 04:33 PM   #2298
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Simplistic Mosfet HV Shunt Regs
If the leds don't light up, its useless to do right now. Lets see the leds thing. Are they 20mA types? What is their Vf spec? Do you set their cut straight rim side aligned with the D symbol printed on the PCB?
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Old 30th December 2011, 04:36 PM   #2299
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Yes are 1.8V 20mA.

Yes I verified the LED's orientation with a 9V battery.
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Old 30th December 2011, 04:40 PM   #2300
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Simplistic Mosfet HV Shunt Regs
OK lets look back. You got two boards there, as I know well circulated and practiced boards. One red, one green board. Two different guys SSHV1 boards. You assemble by the book and they poof the same way. Had made one of those before? Worked? If yes, what changed in the configuration you plug them in now?
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