Problems with 12V and 5V lines on a PC ATX supply

That's the bit I want explaining, how does it get confused with zero load, but is happy with a tiny or a huge load?

Also, how hard would it be to have a dummy load inside the PSU that was switched in if it detected the 12V was off?

They're not actually. They're twice the CIT supplies, but still quite sensible compared with non-PC PSUs.

I'm just going by what has been said by experts on stackexchange.

Reply to
Commander Kinsey
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Maybe because its not well designed.Switch mode supplies tend to be designed with a minimum load in mind in my experience. Brian

Reply to
Brian Gaff (Sofa

AS I said, its all part of the fact that its switch mode, and the regulation is not a classic series regulator, its a feedback loop controlling the oscillation of the switch mode part, its all interconnected. I first encountered this weirdness many years ago when a pc I had had some tacky bright leds all down both sides of the front, making it look terrible and for me making my failing sight rebel. So I thought, simples, unconnect them. It was then that the pc decided it either would not start correctly or would not shut down an and lots of tother things went weird. Reconnecting the leds and all was well again. In the end I hid the leds in the case. Out of sight out of mind. I expect the spiders enjoyed it. Brian

Reply to
Brian Gaff (Sofa

I can understand it going off with a high load, but zero or low load is just weird.

Reply to
Commander Kinsey

That's weird. Surely the LEDs weren't the only thing drawing power at that voltage?

Reply to
Commander Kinsey

I might try this, as it looks very much like the one I bought to fit in the local restaurant to power a huge amount of LED mood lighting, and that's still working after 5 years:

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have a 1kW 220V to 12V version, with trimmable output. 2/3rds of the price of a used 1kW Corsair PC PSU. Although if the trick with the headlamp bulb keeps working, I have a shelf of CIT PSUs to use up. The PC is certainly much more stable now. I'm getting a steady 11.5V at the graphics card inputs, which beats 10-10.5V.

Reply to
Commander Kinsey

I'm surprised there aren't dedicated transistors for every line.

Reply to
Commander Kinsey

How can it be so hard to monitor the voltage when there's no current flow? And how can 12V be down at 10.5V when 5V is up at 5.2V?

Reply to
Commander Kinsey

Why do those two detections need to be related?

It's getting plenty current through the 12V part, which must be physically larger (as in more coils) than the 5V part. I can draw the full 56A from 12V, and it's still unhappy?! By the way, the 5V is only 33A max. So, 1.5A on 5V makes it happy and 56A on 12V does not? What gives?

The guy who designed that circuit must have been on some wild drugs. "I know, let's make things more complicated than necessary and make assumptions about the current draws when it will be connected to a computer that could have any number of different parts operating at different voltages, some of which may not be used some of the time."

Reply to
Commander Kinsey

Or buy a single power supply that can handle the full load. They DO exist, but they ain't cheap!!

Reply to
Clare Snyder

There's a group sci.electronics.design that still has life. They might like the diversion from arguing the merits of the electoral college.

Reply to
Dean Hoffman

The scottish wanker loaded the same question to all the electronic groups at the same time. Playing off one set of groups against the other.

Reply to
Andy Bennet

I was born here, and voted independance.

Reply to
Commander Kinsey

Playing off? WTF are you talking about? Since I don't inhabit those groups, I don't know which have any traffic or anyone who can answer, hence I asked in all the relevant ones.

Reply to
Commander Kinsey

I shall try it.

Reply to
Commander Kinsey

You are asking all the same f****ng questions as you have done here - and amazingly getting all the same answers. But still you persist.

Reply to
Andy Bennet

Of course I'm asking the same questions in different groups, to perhaps find someone who has the intelligence to answer them.

Reply to
Commander Kinsey

We all did, you are too stupid to understand the answer.

Reply to
Rod Speed

Did you get your "Does a parrot's foot conduct electricity?" post answered on the s.e.design group?

Reply to
Andy Bennet

I understand alright - that designers are morons.

Reply to
Commander Kinsey

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