Help from someone who understands Power Supplies...

[mattfaske]

I'm building a small self-powered speakers system, and I ordered the power supply off ebay (cheap from china). I'm hoping someone on this board can help me understand what the seller means when he says "adjustable: when you adjust it on 10uf/50v, the compacitor need bigger if you use longer time. if you do not need the adjustable stablization, pls simply remove the 10uf/50v"



Thanks!

[Æ]

Re: Help from someone who understands Power Supplies...

I'm building a small self-powered speakers system, and I ordered the power supply off ebay (cheap from china). I'm hoping someone on this board can help me understand what the seller means when he says "adjustable: when you adjust it on 10uf/50v, the compacitor need bigger if you use longer time. if you do not need the adjustable stablization, pls simply remove the 10uf/50v"

[ATTACH=CONFIG]60573[/ATTACH]

Thanks!

Don't you just love the way the Chinese try and translate pertinent information into english?

There is a device attached to the heatsink, likely a voltage regulator. Could you post a clear picture of the device or look at the device and tell us what the number(s) on it are? Some regulators are fixed and some are adjustable. Better yet would be a look at the schematic and or parts list for your power supply. Does the seller provide you with any documentation? Any links?

[hongrn]

Re: Help from someone who understands Power Supplies...

I think the trimmer adjusts the output voltage of the power supply. If you hooked up a 12VAC transformer to this module, your rectified voltage will be about 17VDC, so theoretically, you can adjust the pot to have an output between 5VDC to 17VDC, for example. Just hook up your transformer to the module, and use a DMM to measure the DC output while playing with the trimmer. Remember that the capacitor on the module is only rated at 50V, so be careful not to exceed 45VDC, otherwise, expect kaboom!

[Dirttracker73]

Re: Help from someone who understands Power Supplies...

It looks like it has 4700uF 50V cap for the rectifier section. The poor translation may be trying to tell you to not exceed this rating and if rectifcation is not needed, you can bypass the big diodes and cap. The chip may be LM338 or LM317. They are both adjustable. The LM317 is good for about 1 amp and the LM338 about 5 amps.

One other note, the more differential between input and output, the hotter the chip will run. In reality, you should keep it less than about 8 volts. For example; if your input voltage is 30 VDC, the output should be between about 22 to 27 VDC. If you are putting in 30 VAC, rectifying to 40 VDC and regulating it down to 24 VDC, the chip will run very hot. The chip is probably rated for a 30 V differential but it will burn at that dfferential. The LM338 works pretty well within its limits and has good ripple rejection.

[mattfaske]

Re: Help from someone who understands Power Supplies...

Thank you for the help... The regulator is an LT1083. 4700UF/50V,working voltage：input AC0-34V, output DC0-48V, current：0-10A.

It does have a trimmer that adjusts the ouput voltage. I'm just not clear as to what the seller is trying to say in regards to the little 10uf/50v capacitor.

My plan is to use this board to provide 12VDC to a small 15w amp, using a 24V 4A transformer.

[NickS]

Re: Help from someone who understands Power Supplies...

Just leave the capacitor in. It's either across the potentiometer or the output and will probably provide better stability. Maybe they meant to leave it out if you replaced the potentiometer with a fixed resistor to provide a fixed output voltage.

[Æ]

Re: Help from someone who understands Power Supplies...

Thank you for the help... The regulator is an LT1083. 4700UF/50V,working voltage：input AC0-34V, output DC0-48V, current：0-10A.

It does have a trimmer that adjusts the ouput voltage. I'm just not clear as to what the seller is trying to say in regards to the little 10uf/50v capacitor.

My plan is to use this board to provide 12VDC to a small 15w amp, using a 24V 4A transformer.

Take a look at this data sheet.
http://cds.linear.com/docs/en/datasheet/108345fh.pdf

[JimHRB]

Re: Help from someone who understands Power Supplies...

Why are you going to use a 24VAC transformer when you want 12VDC output? Seems like a 12VAC transformer would be a better choice.

[hongrn]

Re: Help from someone who understands Power Supplies...

In addition, if you only need 12VDC to power a 15W amp, why not use a 12VDC/5A power supply like this one, and do away with the power supply module completely? I have a 19.5VDC brick that powers a 25W X 2 Class D amp in my Sonata sound bar, and that has been going great for over a year.

http://www.parts-express.com/12-vdc-...-plug--120-056

Why are you going to use a 24VAC transformer when you want 12VDC output? Seems like a 12VAC transformer would be a better choice.