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merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by Backbones So What current is your transformer providing for each secondary? 30VA What value have you for R101? 3R3 Four LEDs green, correct? YES What is the voltage drop across each green LED? 1.8-1.9V What value for C105? 10.000Uf Chris

 20th October 2011, 05:01 PM #612 Backbones   diyAudio Member   Join Date: Sep 2008 Transformer current sufficient. 4 times 1.9V = 7.6V Say current draw of 700mA = Vgs of about 5.5V. 7.6-5.5=2.1V I=V/R. I=2.1/3.3. I=640mA. Not enough current for 700mA. R101 needs to be 3ohm or lower (2.1/0.7). I don't know up to what current the BiB is designed to go. chris
cersepn
diyAudio Member

Join Date: Feb 2010
Quote:
 Originally Posted by Salas Use 3 1.9V leds and 1.2R 2W setting resistor (R101 etc.) for 0.5A available if you can't find 1.3R.
Hmm, Salas just to confirm, 1.9V = RED LEDs, yes? Because i saw other people who used the regs in the same application and they used the green LEDs in Dx02,x03,x04 instead. Is it because their current used is different?

AndrewT
R.I.P.

Join Date: Jul 2004
Location: Scottish Borders
Quote:
 Originally Posted by coolhead Voltage across R301: 6.3Vac trans = 1.31V 9Vac trans = 1.36V R301 is 10ohm The output is the same 3.3V, the different will be CCS current of 50mA.
and now turn the mains supply voltage down to suppliers specified minimum. Measure again.

The fact that you have already lost 50mV tells me you are getting close to dropping out.
__________________
regards Andrew T.

merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Measured voltage accross R1 2.37 V : 3R3 = 718mA

BTW enough for B3...
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Last edited by merlin el mago; 20th October 2011 at 05:12 PM.

merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by cersepn Hmm, Salas just to confirm, 1.9V = RED LEDs, yes? Because i saw other people who used the regs in the same application and they used the green LEDs in Dx02,x03,x04 instead. Is it because their current used is different?
Different voltage.

Backbones
diyAudio Member

Join Date: Sep 2008
Quote:
 Originally Posted by merlin el mago Measured voltage accross R1 2.37 V : 3R3 = 718mA
OK. After calculation errors it is about the right current levels. The drop across the LEDs depends on their current I believe to some degree.
If you are supplying the right current at the reg level one has to ask if the load is drawing more than this?
Chris

merlin el mago
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by Backbones OK. After calculation errors it is about the right current levels. The drop across the LEDs depends on their current I believe to some degree. If you are supplying the right current at the reg level one has to ask if the load is drawing more than this? Chris
Extracted from leonvb BIII manual in the TP site:

"The standard board requires an input voltage of 5.25V and it draws approximately 440mA when one is using the recommended set of Trident shunt regulators"

Backbones
diyAudio Member

Join Date: Sep 2008
Quote:
 Originally Posted by Salas Looks 5ish to me, better calculate based on Vgs=5V. Also your LEDS maybe ~1.9V at the small current they will run, their spec voltage drop Vf is given at 20mA nominal usually.
From an earlier post.
Chris

 20th October 2011, 05:19 PM #620 merlin el mago diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe I don't understand, could you elaborate?

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