SMPS request

[ali-r]

hi every body. who can give me a mains (220v) to 2*35v at 3 Amp smps?
i want it to supply a STK4192 Audio Amp.

 

[hjames]

Either buy an (expensive) SMPS or build a nice fat linear power supply (toroid transformer, etc). Trying to build a offline voltage switcher would double as an intro into pyrotechnics in the best case, and a demonstration of CPR and defibrillator machines in the worst.

 

[Tarsil]

Realy need a stabilised PS for that PA?
A lot, if not most, are designed to operate quite well without one.

 

[ali-r]

PA does not need a stabilised PS. I tried to convert a PC power supply to +/-35v . but i can not untill this time. it is difficult to modify it. can u help me?

 

[justDIY]

https://www.mpja.com/productview.asp?product=16034+PS

36v @ 4a, cheap too as far as psu go.

 

[Tarsil]

PA does not need a stabilised PS. I tried to convert a PC power supply to +/-35v . but i can not untill this time. it is difficult to modify it. can u help me?

I've modified a PC PS for higher voltages. But for 35V...nope...Use the app notes for a specialized IC. When u find a sol...pls post it I'm interested.
Btw ...I can buy a toroidal transformer 2X25V, 350VA for...40$. Prob same for u. Just put a bridge and some caps and.....voila...problem solved. Also u can buy a used transformer for spots. It's quite cheap (6-7$) but u have to rewind the secondary .
PS. The cheap SMPS are quite noisy.

 

[justDIY]

three 12v switchers in series would yield 36 volts ... use a hefty diode to drop down to 35.3v

 

[Tarsil]

three 12v switchers in series would yield 36 volts ... use a hefty diode to drop down to 35.3v

3X12 switchers in series? Sure that's OK? Have u tried puting SMPS's in series?

 

[justDIY]

yes, I have 4 switchers in series, rigged up in a box ... so I can tap 12, 24, 36 and 48v ... mind you, these are just cheap table-top type switcher supplies (3a each), more advanced switchers might draw expection to this practice.

so far no fires, no blown fuses or caps (fuses are a good idea by the way)

 

[Hero999]

I don't know about PC power supplies, aren't the outputs usally earth bonded? It it's the case then the answer is no.

Some of those small switchers in power bricks aren't even regtulated. The one in an old mobile phone charger certainly isn't, it's just a transfromer with a blocking oscillator driver on the primary and a rectifier and filter capacitor on the output, plus a small resistor which I assume loads the output so the voltage doesn't get too high.

 

[Tarsil]

yes, I have 4 switchers in series, rigged up in a box ... so I can tap 12, 24, 36 and 48v ... mind you, these are just cheap table-top type switcher supplies (3a each), more advanced switchers might draw expection to this practice.

so far no fires, no blown fuses or caps (fuses are a good idea by the way)

Well...I've heard that u CAN'T put in series PC PS (at least older models). About those switchers u've put in series...can u elaborate about the model?
I realy could use something like 36/48V@3A

 

[Nigel Goodwin]

Well...I've heard that u CAN'T put in series PC PS (at least older models). About those switchers u've put in series...can u elaborate about the model?
I realy could use something like 36/48V@3A

I don't see as it's any problem? - obviously you have to break the chassis connection to zero volts (or insulate them from each other) - and you need to provide a minimum load for each one. It would also be a seriously good idea if they are all IDENTICAL types!.

 

[justDIY]

my switchers are similar to this, except 3a instead of 2a

**broken link removed**

I concur with Nigel's recommendation of isolating the power supply chassis if you're going to use ATX type supplies, as well as throw a few watts of resistors on the un-used rails, just to keep things happily regulated.

 

[Tarsil]

I don't see as it's any problem? - obviously you have to break the chassis connection to zero volts (or insulate them from each other) - and you need to provide a minimum load for each one. It would also be a seriously good idea if they are all IDENTICAL types!.

Well...I'l try

 

[ali-r]

i rebuilt atx and use a new hand-wond transformer. bur its driver transistor bacame very hot( with hearsink and smal fan). i will told u later what i did