How to decrease the voltage?
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 19th December 2006, 04:48 PM #1 sunny   diyAudio Member   Join Date: Oct 2004 How to decrease the voltage? Hi Friends, I have Yamaha PSR-3000 electronic keyboard and it needs 16 volts switching power supply and i dont have company adapter and at present i have another switching power supply adapter of 19 volts DC of 3.42 Amperes and my keyboard requires 16 volts DC,2.4 Amperes. So what resistor i should i use in series to get 16 volts,2.4A from 19 volts,3.42 power supply?Your help is highly appreciated and please give the resistor value and its wattage. Thanks, SUNNY.
 19th December 2006, 07:21 PM #2 I_Forgot   diyAudio Member     Join Date: Jan 2005 Location: Phoenix, Az. Inserting a resistor in series with the supply isn't a good way to do the job. If you were going to power a light bulb you could use that technique, but you risk destroying the keyboard because it doesn't draw a constant 2.4 A from it's 16V supply. Switchers (and all other voltage regulators) constantly compare the output voltage to a stable reference. If you tweak the reference voltage you can set the output to 16V. That can be done with a resistor or two, but you have to find the reference in the circuit. I_F
lineup
diyAudio Member

Join Date: Dec 2005
Location: the north
Quote:
 Originally posted by I_Forgot Switchers (and all other voltage regulators) constantly compare the output voltage to a stable reference. If you tweak the reference voltage you can set the output to 16V. That can be done with a resistor or two, but you have to find the reference in the circuit. .

Yes.
If you could draw exact circuit with resistor values
at that reference point or PIN of that switch supply
it wouldn't be hard to give directions.
If you posted it.

There are many in forum that are Really Power supplies EXPERTS.
Even when it comes to complicated switching circuits.

But this might not be so easy to do.
Probably not a schematic of that supply to find in internet
and to draw a copy just from looking at PCB, is often difficult.

Hope you can solve to get a good 16 Volt supply.
Otherwise, how can you be happy this Christmas

lineup
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 20th December 2006, 04:05 AM #4 sunny   diyAudio Member   Join Date: Oct 2004 Now what should i do to get 16 volts ouput at the keyboard?please give me the solution and now i have to play my keyboard for christmas programmes,please help me. Thanks, SUNNY.
gmphadte
diyAudio Member

Join Date: Jul 2003
Location: Dona paula, Goa
Not a PRO solution...

This is a quick solution
see attachment

TIP 122 should be mounted on a heatsink.
5K6 resistor should be 1 Watt
Connect 1k resistor at the output and measure the output voltage. Confirm it is correct and then connect as needed to the keyboard.

Gajanan phadte
Attached Images
 19 16v.jpg (23.1 KB, 116 views)

 20th December 2006, 09:48 AM #6 sunny   diyAudio Member   Join Date: Oct 2004 Hello Gajanan phadte, Thanks for your circuit,now i'll purchase the components and i will try this circuit for my keyboard and is this 560,100ohms resistors of 1/4 watt?and is 0.1 disc ceramic? Instead of using this circuit and if i simply connect 3 or 4 BY255 in series,is there any problem?please clarify. MAY GOD BLESS YOU. Thanks, SUNNY.
lineup
diyAudio Member

Join Date: Dec 2005
Location: the north
Quote:
 Originally posted by sunny Instead of using this circuit and if i simply connect 3 or 4 BY255 in series,is there any problem?please clarify.
no, i dont think so.

If you buy a number of Diodes whatever type that can take at least 5 Ampere
than you should be able to see how many diodes you need
to get ~16 Volt.

I have used this way in some cases myself, to get smaller Volt Drop.

I think it will be just fine,
because a circuit like you will use, is not require precise 16.000V.

Think about in car .. stuff you use in Car,
will work well and can take any voltage: within range like 11.5 Volt - 16 Volt.
If what you put in your car, can not take this
then it is not suitable for car battery/car generator use.

==============================================
==============================================

Go for simple but good:, your own solution:
Buy a number of 5-10 Ampere diodes.
Not critical what type, as long as they can take 5A.

Than make some tests:

1) Start by adding 5-6 diodes!
2) If voltage is below 16 Volt, than remove 1 diode
and repeat until you get 16.0 volt, or just a litle bit MORE.
Maybe 16.1 16.2 16.3 Volt.
3) Then I am almost sure this will work forever!

Think will be no problem at all for get gear working
before Christmas 2006.

Have a good time!
lineup
__________________
lineup

 20th December 2006, 10:53 AM #8 gmphadte   diyAudio Member   Join Date: Jul 2003 Location: Dona paula, Goa 1/4 Watt for 560 and 100 is OK 0.1 ceramic is ok. Diode solution U have to buy 1N5404. 8/9 jn number U have to drop 3 volts and each diode will drop about 0.4 volts Gajanan phadte
 20th December 2006, 04:12 PM #9 sunny   diyAudio Member   Join Date: Oct 2004 Thanks to all for helping me. MAY THE LORD MAKE YOUR CHRISTMAS ESPECIALLY HAPPY AND BLESSED. sunny.
 26th December 2006, 12:16 PM #10 sunny   diyAudio Member   Join Date: Oct 2004 Hello Friends, I have played my keyboard for the christmas programmes very well using the modified switching power supply.I have connected four 6A4 diodes in series on positive line and i'm getting 16.5 volts at the keyboard. Now another problem has started,the four 6A4 doides are getting too hot and they are burning my fingers if i touch them,I can't understand why the dodes are getting very hot ?The current rating of diodes are 10A and my keyboard requires only 2.5 A. Is there any solution to this problem? Thanks, SUNNY.

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