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psu voltage readings


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#16
happyrock

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it has to be a bad sensor...
is this Chassis fan 7584 RPM...reading right :)... this must sound like a vacuum cleaner running or a small plane taking off...
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#17
Neo31801

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i never hear the fan running so this must be a faulty reading as well

thanks to all of those that replied and even though there was nothing to "fix" i learned a lot about the psu so thanks for that too!


im usually plagued with computer issues so expect to see me around! :)
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#18
happyrock

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your welcome...and thanks for letting us know... :)
do come back... someone is always here to help.. :)
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#19
Neo31801

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1 more question before i leave this topic....if the readings are wrong could it be a problem with the mobo or just that its a cheaper HP model mobo that has faulty readings since it wasnt meant for this kinda use ?
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#20
123Runner

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The reading of the fan sensor and voltage could be the board or the program. The program being that the sensor is not recognized. I am not concerned about the fan because you can see the fans are working.
As for the 3.3 vdc, I am more concerned about that. The only way to be sure on that is with a PSU tester, or someone that has a digital meter (and knows what they are doing) and can take a reading on the connector.
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#21
Neo31801

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The reading of the fan sensor and voltage could be the board or the program. The program being that the sensor is not recognized. I am not concerned about the fan because you can see the fans are working.
As for the 3.3 vdc, I am more concerned about that. The only way to be sure on that is with a PSU tester, or someone that has a digital meter (and knows what they are doing) and can take a reading on the connector.


would this be what i was looking for?

http://cgi.ebay.com/...4#ht_1794wt_939

Edited by Neo31801, 05 December 2009 - 11:09 AM.

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#22
123Runner

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The one you reference will only show if the voltage is present. It will not tell you what it actually is.
Also, and this is important...The instructions for that tester are telling you to do something that is very dangerous. The 1st step is to turn the PSU on AND then connect the tester and peripherals for testing under load.
You never plug something in when there is power applied!


I will give you Digerti's canned speech on PSU's
Unfortunately, there is no sure fire way for most users to test a PSU properly. Here is my canned text on testing PSUs.

To properly and conclusively test a power supply unit (PSU), it must be tested under various realistic "loads" then analyzed for excessive ripple and other anomalies. This is done by a qualified technician using an oscilloscope or power analyzer - sophisticated (and expensive) electronic test equipment requiring special training to operate, and a basic knowledge of electronics theory to understand the results. Therefore, conclusively testing a power supply is done in properly equipped electronics repair facilities.

Fortunately, there are other options. I keep a FrozenCPU Ultimate PSU Tester in my tool bag when I am "in the field" and don't have a good spare power supply to swap in. While not a certain test, they are better than nothing. The advantage of this model is that it has an LCD readout of the voltage. With an actual voltage readout, you have a better chance of detecting a "failing" PSU, or one barely within specified ATX Form Factor Standard tolerances. Lesser models use LEDs to indicate the voltage is just within some "range". These are less informative, considerably cheaper, but still useful for detecting PSUs that have already "failed". Newegg has several testers to choose from. All these testers contain a "dummy load" to fool the PSU into thinking it is connected to a motherboard, and therefore allows the PSU to power on, if able, without being attached to a motherboard - great for testing fans, but again, it is not a true load or suitable for conclusive testing.

As mentioned, swapping in a known good supply is a tried and trued method of troubleshooting used for centuries, even by pros. Remove the "suspect" part and replace with a "known good" part and see if the problem goes away.

I do not recommend using a multimeter to test power supplies. To do it properly, that is, under a realistic load, the voltages on all the pins must be measured while the PSU is attached to the motherboard and the computer powered on. This requires poking (with some considerable force) two hard and sharp, highly conductive meter probes into the main power connector, deep in the heart of the computer. One tiny slip can destroy the motherboard, and everything plugged into it. It is not worth the risk considering most multimeters, like plug-in testers, do not measure, or reveal any unwanted and potentially disruptive AC components to the DC voltages.

And remember, anything that plugs into the wall can kill. Do not open the power supply's case unless you are a qualified electronics technician. There are NO user serviceable parts inside a power supply

Thanks to Digerati for the above instructions
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#23
Neo31801

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so i should be ok with picking up a FrozenCPU Ultimate PSU Tester ?
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#24
123Runner

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I have never used one. based on the description it will do what you want.
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#25
Neo31801

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I have never used one. based on the description it will do what you want.


ok thanks...i also found a few electric repair shops in the area, but they mostly service TVs...ill call monday and see if they're able to check the psu's for me

thanks again for your help

ill post back when i can get some accurate readings
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#26
Neo31801

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update:

ive called two local electrical appliance repair places here locally and both told me that the 1.78 reading on my psu's is because my computer was designed to put out (or receive) 1.78v...there was a slight language barrier with both techs but they both said there was no sure way to check the psu other than replace it (lol) even after i told them 3 different psu's read the same voltage

they also said that the 3.3 reading didnt matter , only the 5v and 12 v mattered.... and something about my processor and chipset made the 3.3 read the 1.78 volts...one also mentioned something about the CMOS settings?

im completely lost on this stuff

any of this make any sense?

he also said hooking a volt meter to it could not insure a more accurate reading due to electrical noises

i have one more place here locally to try, i was just wondering how this sounded to someone here
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#27
Major Payne

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The "local electrical appliance repair places" should tell it all. I trust these guys here more than any local appliance store even if they claim they "repair" computers. Personally, I think you either have a bad sensor or there is a bad cable connections from the pin to motherboard.

Not to confuse matters, but "voltmeters" come in many different varieties. I always used a Fluke True RMS one, but appliance repair places normally do not need the sophistication of a DMM like that.

Those PSU's need to be properly loaded. Some (most?) use switching power supplies and will either not start with no load or will shutdown. The old ones use to just destroy themselves when turned on with no load.

The definitive test is to measure that one pin voltage with and without the proper load on it while keeping all other sources properly loaded. If you read correctly with no load and the 1.76-volts loaded, then the supply is more than likely defective. If both read fine, then the sensor/pin connection is bad. If the motherboard has that voltage clamped with a zener diode, it could be bad.

You do need someone who has GOOD troubleshooting experience to determine the actual problem instead of giving you all the BS you've been given from those appliance stores.
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#28
Neo31801

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You do need someone who has GOOD troubleshooting experience to determine the actual problem instead of giving you all the BS you've been given from those appliance stores.


i was at the same conclusion....i just dont have the $30 to drop on a psu tester that i may only use once and im surely not going to try stickin a volt meter lead into a powered up computer

theres one more place on my to call list...gonna give him a try tomorrow + he is with in walkin distance so i can actually go face to face with him so i can fully explain this situation

thanks for your reply
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#29
Neo31801

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wow i lucked up and found a guy within walking distance thats a retired AirForce comp tech that now owns his own business

anyways he stopped by this afternoon with his "FrozenCPU Ultimate PSU Tester" and the psu came up reading the voltages exactly where they should be

looks like the sensors were the culprit with the low voltage readings

once again I thank everyone that posted in this topic and I will recommend anyone i know to this site for help

you guys are awesome!!
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#30
123Runner

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I am glad you got that resolved. It is at least nice to know it was the sensor. Thanks for letting us know.
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