The simplistic Salas low voltage shunt regulator - Page 200 - diyAudio
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Old 5th March 2010, 10:24 PM   #1991
iko is offline iko  Canada
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Don't know what you mean. But I think the mosfet is fried.
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Old 5th March 2010, 10:27 PM   #1992
massimo is offline massimo  Italy
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Did he test the mosfet as it were a bjt?
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Old 5th March 2010, 10:55 PM   #1993
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Don't know, I hope not. But then he mentioned hfe.

When I'm in a hurry I test the mosfet out of the circuit with the diode tester. If I hear a beep, that's it, gone. A better test is to charge it with the diode tester a bit, then discharge it by touching the other two pins with the fingers.
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Old 5th March 2010, 10:57 PM   #1994
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Quote:
Originally Posted by ikoflexer View Post
Don't know what you mean. But I think the mosfet is fried.
Ok I will replace for another new. Tomorrow I will let you know. Thks & good night.

Last edited by merlin el mago; 5th March 2010 at 11:02 PM.
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Old 5th March 2010, 11:22 PM   #1995
iko is offline iko  Canada
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Good night.

Just so you know, for testing, The CCS circuit alone can be tested. This is how.

1) 200mA fuse just before R1, in series.
2) Disconnect the drain of Q1 (pin 2), leave it disconnected, or connect from drain to ground a 4k7 resistor, 1W
3) replace R1 with a value that will give you a current of about 25mA total.

The LEDs should be on and you should be able to observe a limit current of about 25mA through R1. The current should be limited even if you short the drain of Q1 to ground.

If this works, then you got a functioning CCS, and you can move on to the next part, getting the shunt working properly.
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Old 5th March 2010, 11:50 PM   #1996
klewis is offline klewis  United States
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Quote:
Originally Posted by Salas View Post
You want the over 40V one capable in symmetric that LaOde uses for D1 and first was used in Italy on EB class A kit amp driver stages?
Salas,

I would like to produce a regulated voltage somewhere between 40 and 50v with about 200mA current both positive and negative. I plan on using it to supply the LME49811 and maybe a second pair to power the driver transistors.

Thanks again.

Ken L
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Old 6th March 2010, 02:31 AM   #1997
Salas is online now Salas  Greece
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That one will run +/-180mA if your Leds can reach 2V Vf for about 2.5mA. Else, about 150mA. R1 sets that. ICCS=(Vf3LEDStot-Vgs)/R1. Fix it given your actual parts. The trimmer gives you an adjustable Vout. Don't ask more than 65V out. You can use BF245A if you can't get 2N5457, don't use anything more than 3mA IDSS collector load, so to keep the error amp BC546B dissipating conservatively. Remote sensing is recommended. You have seen how on the one I showed for Merlin a few pages back. Good luck.
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File Type: gif V1-0-180mA-45V.gif (7.7 KB, 586 views)
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Old 6th March 2010, 10:30 AM   #1998
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Quote:
Originally Posted by ikoflexer View Post
Good night.

Just so you know, for testing, The CCS circuit alone can be tested. This is how.

1) 200mA fuse just before R1, in series.
2) Disconnect the drain of Q1 (pin 2), leave it disconnected, or connect from drain to ground a 4k7 resistor, 1W
3) replace R1 with a value that will give you a current of about 25mA total.

The LEDs should be on and you should be able to observe a limit current of about 25mA through R1. The current should be limited even if you short the drain of Q1 to ground.

If this works, then you got a functioning CCS, and you can move on to the next part, getting the shunt working properly.
Thks for your patience with me, sorry in advance to ask a lot of questions.

Wich value to replace R1 to have a current of about 25mA total?
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Old 6th March 2010, 10:41 AM   #1999
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Quote:
Originally Posted by ikoflexer View Post
Q1, the ccs mosfet is either not connected right, or burnt? You might want to take it out and test with DMM.
Sorry for newbie question: How to test with DMM?
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Old 6th March 2010, 10:57 AM   #2000
massimo is offline massimo  Italy
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The easiest way: DMM set for 2kohms. Probe between all legs (i.e. 1 and 2, 1 and 3, 2 and 3) Repeat inverting polarity (if you put the red probe on leg 1 and black on leg 3, invert them: red on 3 and black on 1).
Eventually compare with a new one, but if there is one short, it's gone. Replace.
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