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Hardware Hacking The hammer and tongs school of Overclocking. (NOT for the beginner and you assume all risks)


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Old 27th January, 2002, 04:00 AM
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Powersupply, 12V rail only puts out 9 V ?

thats right, I bought a used power supply (Power man 235 Watt) to test an electonic circuit. I tested the voltage acoss the 12V rail and it reads only 9 Volts, what gives? This won't make a huge difference in what I'm doing I don't think, but still I'm wondering.

I tested by putting the test leads directly into the 12V rail on the power plug.
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Old 27th January, 2002, 10:15 AM
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Did you test it with a load on the 5V line, or did you just turn it on without anything but the measurement equipment connected?

If you didn't have a load on the 5V line, find something with a few ohms resistance (car lightbulb of some description) to put across the 5V line whilst you test the 12V line.

The reason you only got 9V out, is that the converter that generates the 12V line is the same converter that produces the 5V line. Hence the output of the two is linked. If the 5V goes up, so does the 12V...

The regulation circuitry is designed to monitor the 3.3V and 5V lines. It doesn't monitor the 12V line (except for overvoltage). As the 12V control signal is derived from the same circuitry that controls the 5V control signal, it goes all pear shaped with no load.

Of course, the other alternative is that your PSU has a faulty rectification diode (or synchronous rectifier).

AidanII
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Old 27th January, 2002, 08:18 PM
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Quote:
Originally posted by AidanII
Did you test it with a load on the 5V line, or did you just turn it on without anything but the measurement equipment connected?

If you didn't have a load on the 5V line, find something with a few ohms resistance (car lightbulb of some description) to put across the 5V line whilst you test the 12V line.

The reason you only got 9V out, is that the converter that generates the 12V line is the same converter that produces the 5V line. Hence the output of the two is linked. If the 5V goes up, so does the 12V...

The regulation circuitry is designed to monitor the 3.3V and 5V lines. It doesn't monitor the 12V line (except for overvoltage). As the 12V control signal is derived from the same circuitry that controls the 5V control signal, it goes all pear shaped with no load.

Of course, the other alternative is that your PSU has a faulty rectification diode (or synchronous rectifier).

AidanII
It was tested with nothing on either the 5V or 12V rail. I'll give a try to what u suggested and see if it makes a difference.
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Old 28th January, 2002, 12:51 AM
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If you only need 12v, I have several Mac LC power supplys. They are really small, and they only put out 5 and 12. Like an AT PSU, only simpler. They are a little smaller than the PSU you find in most external HDD enclosures. You are really close, so I don't even need shipping. send me an addy. (I'm still shipping it, I just am not troubled by the cost of shipping from Kankakee to Chicago. )
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Old 28th January, 2002, 07:42 PM
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Quote:
Originally posted by Azriel
If you only need 12v, I have several Mac LC power supplys. They are really small, and they only put out 5 and 12. Like an AT PSU, only simpler. They are a little smaller than the PSU you find in most external HDD enclosures. You are really close, so I don't even need shipping. send me an addy. (I'm still shipping it, I just am not troubled by the cost of shipping from Kankakee to Chicago. )
thank you very much for the offer I think the PSU I have should work fine, but I'll have to test it more to see if it will fit what I'm doing. What is max rated amperage on those MAC PS's just otta curiosity? I've never heard of them. Thanks again for the offer.
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Old 28th January, 2002, 11:57 PM
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Watts=50
Amps=.47

Looking like a not so good idea, I guess. Amps are pretty low.
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Old 29th January, 2002, 01:29 AM
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I appreciate the offer still
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