can we use PC psu's?
- Thread starter tony dB
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Help Support GroupDIY Audio Forum:
owel
Well-known member
They're switching PSU..very noisy.
DrFrankencopter
Well-known member
No transformer, just inductors, switching transistors, caps and regulators. They're good to have on the bench as a source of 5V and 12V for just checking things out though.
The power they produce tends to have switching transients (at around 100Khz or so) which can be almost impossible to get rid of. Transients can be up to 100mV, well beyond where IC opamps have reasonable PSRR.
Cheers,
Kris
The power they produce tends to have switching transients (at around 100Khz or so) which can be almost impossible to get rid of. Transients can be up to 100mV, well beyond where IC opamps have reasonable PSRR.
Cheers,
Kris
dale116dot7
Well-known member
Well, there is a transformer, but it runs at somewhere between 20 and 200 kHz. The supply converts 120 or 240 AC to 360V DC, then chops it up into 360V p-p AC, then runs it through a transformer, high-speed recitifier, and filtering.
Some digital studio gear use a PC-type switcher for the DSP stuff, where they'll need 3.3 or 5V at 30 or so amps, but an old-fashioned linear supply for the mic pres and A-D/D-A converters.
Some digital studio gear use a PC-type switcher for the DSP stuff, where they'll need 3.3 or 5V at 30 or so amps, but an old-fashioned linear supply for the mic pres and A-D/D-A converters.
DrFrankencopter
Well-known member
oops, my bad, I was thinking of DC-DC converters.
Cheers,
K
Cheers,
K
owel
Well-known member
What dale said.... and if you're looking for a ready-made PSU and don't want to build one, look for LINEAR PSUs.
Or just build one, they're easy... the biggest cost is the power transformer at around $12-$16. The rest of the components are fairly cheap. Use bridge rectifiers, some caps for filtering, 3-terminal voltage regulators, some resistors and you're done. Probably $20 total per PSU.
Or just build one, they're easy... the biggest cost is the power transformer at around $12-$16. The rest of the components are fairly cheap. Use bridge rectifiers, some caps for filtering, 3-terminal voltage regulators, some resistors and you're done. Probably $20 total per PSU.
> Is the quality of PC-clones a good source to build other gear with?
There is no 60Hz power transformer.
The whole 20KHz transformer and driver affair is designed for the 5V and 12V outputs, and will need excessive hacking to get more audio-useful outputs. Also many of these things won't start under a light load (most audio is "light" compared to the 150W-300 watt ratings of these boxes), and they all put out huge amounts of slightly-supersonic trash to crap-up your audio.
They also store high voltage on uninsulated parts for maybe hours, maybe days (though usually no more than a minute). So before you open one, un-plug it from the wall and take a nice long tea-break. If you are SURE it has been un-plugged since the P-II died, tear right in. However with 386-era supplies that have been un-plugged for more than a few years, there is some chance the caps have decayed. They can burst when power is applied. Find the old hard drive (bigger is better) as a dummy load, take the PS and HD outside on a concrete patio, and plug it in with a long extension cord. If no smoke/boom in an hour, and the drive is spinning (or trying to), then it is probably good.
Every standard PC supply will yield two 200V filter caps, typically 100uFd-470uFd depending on original cost. If you have a 150V rail to smooth, these are fabulous.
You can also salvage several 6V or 16V caps in the 100uFd to 1,000uFd range, clustered around the output wires.
The heatsinks can be useful; also the power entrance connector.
The controller IC is good for general purpose PWM, but new ones are so cheap it is hardly worth ripping one off a board.
There are two sets of power devices on the heatsinks. Toward the input side are two 400V transistors, but they could be BJT, FET, or IGBJT, and won't have any standard part-number so you can look them up. Good luck. The parts on the other sinks are high current low voltage fast rectifiers in transistor-like packages-- if you need a fast 50V rectifier you can play around with these.
There are sometimes one or two linear negative regulators like 7912, to derive the low-current -12V and -5V rails defined in the IBM PC standard (BTW, in all my years I've only seen one card eat -5V).
There is usually (in old good supplies) a thermistor in the AC input, before the main wall-power rectifier, to limit inrush current. These could be handy in any big supply that dims lights when you flick it on.
There is no 60Hz power transformer.
The whole 20KHz transformer and driver affair is designed for the 5V and 12V outputs, and will need excessive hacking to get more audio-useful outputs. Also many of these things won't start under a light load (most audio is "light" compared to the 150W-300 watt ratings of these boxes), and they all put out huge amounts of slightly-supersonic trash to crap-up your audio.
They also store high voltage on uninsulated parts for maybe hours, maybe days (though usually no more than a minute). So before you open one, un-plug it from the wall and take a nice long tea-break. If you are SURE it has been un-plugged since the P-II died, tear right in. However with 386-era supplies that have been un-plugged for more than a few years, there is some chance the caps have decayed. They can burst when power is applied. Find the old hard drive (bigger is better) as a dummy load, take the PS and HD outside on a concrete patio, and plug it in with a long extension cord. If no smoke/boom in an hour, and the drive is spinning (or trying to), then it is probably good.
Every standard PC supply will yield two 200V filter caps, typically 100uFd-470uFd depending on original cost. If you have a 150V rail to smooth, these are fabulous.
You can also salvage several 6V or 16V caps in the 100uFd to 1,000uFd range, clustered around the output wires.
The heatsinks can be useful; also the power entrance connector.
The controller IC is good for general purpose PWM, but new ones are so cheap it is hardly worth ripping one off a board.
There are two sets of power devices on the heatsinks. Toward the input side are two 400V transistors, but they could be BJT, FET, or IGBJT, and won't have any standard part-number so you can look them up. Good luck. The parts on the other sinks are high current low voltage fast rectifiers in transistor-like packages-- if you need a fast 50V rectifier you can play around with these.
There are sometimes one or two linear negative regulators like 7912, to derive the low-current -12V and -5V rails defined in the IBM PC standard (BTW, in all my years I've only seen one card eat -5V).
There is usually (in old good supplies) a thermistor in the AC input, before the main wall-power rectifier, to limit inrush current. These could be handy in any big supply that dims lights when you flick it on.
thanks for all the replies! :thumb:
i understand way more about pcpsu's now than a few hours ago! :idea:
PRR, i have a mackie d8b that sometimes behaves a bit strange due to powerrailcapacityprobs, do you think i could use caps from the pcpsu's to fix this?
i wouldn't mind having to buy new components, my question popped up when i saw all the obsolete ex-studiogear i just rediscovered in my attick today, i even found 2 atari's upthere :grin:
recycling is cool too if you want to keep the planet cleaner and safer...
:sam: :sam:
i understand way more about pcpsu's now than a few hours ago! :idea:
PRR, i have a mackie d8b that sometimes behaves a bit strange due to powerrailcapacityprobs, do you think i could use caps from the pcpsu's to fix this?
i wouldn't mind having to buy new components, my question popped up when i saw all the obsolete ex-studiogear i just rediscovered in my attick today, i even found 2 atari's upthere :grin:
recycling is cool too if you want to keep the planet cleaner and safer...
:sam: :sam:
