Taking a chance here - problem with DC voltages
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 21st September 2004, 08:55 AM #1 arnoldc   diyAudio Member   Join Date: Apr 2003 Location: Makati Taking a chance here - problem with DC voltages hi all, i know that this is the SS section and i was hoping somebody can help me. i'm in a mess right now trying to make my first DC heaters for my 2A3. i thought that the calculation will be something like AC volts x 1.44 - diode voltage drop = DC volts so i started with a 3.3VAC transformer and 1N5402 in bridge configuration with 4,700uF cap. without load i get 3.6VDC and with load it drops to 1.6V. i tried using a real bridge and got the same result. the 2A3 is rated for 2.5V @ 2A heaters. what and where am i doing it wrong? TIA
 21st September 2004, 09:03 AM #2 Tube_Dude   diyAudio Member     Join Date: Mar 2002 Location: Aveiro-Portugal Hi arnoldc Have your transformer the capacity of supplying the 2 amps without loss of tension? If you are using only a tube. Or the 2 Amps X the number of tubes... __________________ Jorge
 21st September 2004, 10:07 AM #3 arnoldc   diyAudio Member   Join Date: Apr 2003 Location: Makati hi tubedude, the 3.3VAC is coming from a single transformer with multiple secondaries (this is one of them). it is rated at 3A. should this be higher? thanks
Tube_Dude
diyAudio Member

Join Date: Mar 2002
Location: Aveiro-Portugal
Quote:
 Originally posted by arnoldc hi tubedude, the 3.3VAC is coming from a single transformer with multiple secondaries (this is one of them). it is rated at 3A. should this be higher? thanks
I think that maybe the best solution, is to have a higher AC voltage (say 5 or 6 V AC) and after the filter electrolytic to put a dropping resistor and after this resistor another electrolytic.

That way you can achieve two goals:
-Changing the value of the resistor you can "fine tune" the final DC voltage.
-The resistor in conjunction with the last capacitor ,will make a RC filter, that will reduce the ripple noise ,even more.
__________________
Jorge

 22nd September 2004, 12:10 AM #5 arnoldc   diyAudio Member   Join Date: Apr 2003 Location: Makati hi tubedude, that is where i'm heading right now. thanks for the confirmation.
Tube_Dude
diyAudio Member

Join Date: Mar 2002
Location: Aveiro-Portugal
Quote:
 Originally posted by arnoldc hi tubedude, that is where i'm heading right now. thanks for the confirmation.
You are welcome! ...
__________________
Jorge

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