Re: Purpose of -5V and -12V rails
Thanks for the info guys.
phoenixlament
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Last Activity: 03-12-2011, 01:20 AM
Joined: 08-25-2009
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Purpose of -5V and -12V rails
-------------- Background Info.. (skip if you like) --------
I recently found an abandoned low-end P4 computer with a generic power supply inside. The computer was able to boot properly. Suspecting power supply malfunction as a possible cause of the abandonment, I opened the PSU (Y2K YoungYear PS-IV 350-1, actually 250W) and discovered a leaky fuhjyyu and a burnt out resistor, adjacent to a mildy burnt patch on the pcb.
I replaced the leaky fuhjyyu and the other identical fuhjyyu next to it with two working caps (can't remember brands) in an attempt to raise the +12V,-12V,...Last edited by phoenixlament; 06-01-2010, 10:57 PM. -
Re: Gateway with no Capacitors at all!
[B]The caps ARE present[/B], but unlike regular motherboard caps, the caps on this board are [B]solid state, rectangular, and yellow[/B]. I've seen these before on a few older Seanix boards.
If you look carefully, Voltage and Capacitance ratings are written in tiny brown letters on these yellow caps.
I've re-uploaded your image with red circles indicating their location.
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EDIT: "it has caps...sm tantalums!" ... sorry, I must be blind..
Re: Gateway...
Last edited by phoenixlament; 04-27-2010, 01:54 PM.Leave a comment:
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Re: Are Laptop Power Adaptors Linear or Switching?
Okay. Thanks for the replies.Leave a comment:
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Are Laptop Power Adaptors Linear or Switching?
Or does it vary from brand to brand?
Just curious.
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Re: Installing transient filtering
yeah i checked out your yuelin, it does appear very similar.
of course not, this thing will be powering a low end pentium 4 with a mediocre AGP video card, one hard drive, and one CD drive. No plans for high end gaming, will use this for networking and linux experiments.
thanks for the tips y'all. this forum is proving very helpful and you guys really know how to help people get stuff fixed. glad to be part of the community....
Last edited by phoenixlament; 08-30-2009, 01:49 AM.Leave a comment:
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Proper MOSFET testing method
[B]Background: [/B] (Please skip to "Question" section if you don't wanna read alot)
I have gathered about a dozen broken power supplies from 2+ years of computer tech work. Recently I've fixed two of them (blown thermistors, replaced with good ones) - and as some of you might know, the third one just needs one more cap replacement. Fourth one also needs recapping. A few were beyond repair, so I scrapped them for whatever parts were good.
Mysteriously, the rest of my power supplies look just fine. No burn marks on the board, no leaky caps. Fans, thermistors,... -
Re: Installing transient filtering
Successfully installed transient filtering! Put in 2 ferrite coils in place of LF1 and LF2 and 2 ceramic capacitors for CX1 and CX2. Made sure that the ferrite coils were placed the right way. PSU works, although I have no oscilloscope to see how much better it is with the filtering.
By the way, this "upgraded" PSU is an OKIA 450-ATX.
Check this pimped out PS-Unit yo.
Before:
After:
Overall:
Pimped!
...
Last edited by phoenixlament; 08-29-2009, 08:07 PM.Leave a comment:
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Re: Replacing one capacitor with 2 capacitors
Sorry for the late reply. I've been working like crazy the last couple days.
Thanks for the analogy, 370 and yanz. I was always curious why there were so many capacitors everywhere..
Forgot to post this earlier - this PSU is a Sunny Technologies 300W ATX 2.03.
Update:
I've fixed the +5VSB problem(two leaking 470uF caps) with two replacement Teapo 470uF/16V capactiors. 5V rail registers at exactly 5.05V, very nice.
Todo:
Still haven't found a 1500-2000uF/16V capacitor...Leave a comment:
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Installing transient filtering
According to [URL=http://www.hardwaresecrets.com/article/327/4]HardwareSecret's Anatomy of Switching Supplies Tutorial[/URL], some cheap power supplies do not include transient filtering components such as the ferrite coil, X capacitors and y capacitors.
I just fixed power supply 1 (replaced thermistor) and noticed that it does not have complete transient filtering(only has y capacitor). However it has all the correct empty spots on the circuit board where the transient filtering components are supposed to go. (Refer to hardwaresecrets link, that page goes into further detail)...Last edited by phoenixlament; 08-29-2009, 01:33 PM. -
Re: Replacing one capacitor with 2 capacitors
Thanks for the info, 370. will take it into account.
Just wondering - how does a cap's ability to take and release charge have anything to do with filtering currents on a rail? And how come bigger capacitances are better?Leave a comment:
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Re: Replacing one capacitor with 2 capacitors
Thanks for your input. What is the typical percentage tolerance level for replacing caps? And how come when a 1650uF is for -12v, you can use a 1000uF?
And how come 2x 470uF can be replaced with 2x680uF?.. that's roughly 30% difference.
Just curious....Leave a comment:
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Re: Replacing one capacitor with 2 capacitors
Thank you all for your fast replies. 370, I checked out your links. Do the prices listed on digikey include shipping fees as well?
Also, this power supply is for a good old Pentium 3 computer, and it's really not feasible spending anything repairing it since I have a access to a pile other discarded hardware on campus (and their parts)
So I've decided to pull two 470uF,16v good teapos from a discarded Socket462 motherboard, circa 2002. Are Teapos from that time alright?...Last edited by phoenixlament; 08-26-2009, 01:41 PM.Leave a comment:
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Re: Replacing one capacitor with 2 capacitors
lol, it was a TNR fuhjyuu (M) P10. yeah i got fuckjyyued.
the replacement caps i pulled also happen to be fuhjyyus too, except they are working. and after what i've read from here, i'm gonna change my mind about replacing fuhjyyus with fuhjyus. (i know ur laughing at me but hey its only my second post, so forgive me for my noobiness please )
Anyway this cap belongs to a ATX power supply, and it regulates the -12V rail. Due to the cap leakage, the rail is only giving ~11.58v.
Two other bad...Leave a comment:
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Replacing one capacitor with 2 capacitors
I have a dead(leaking) capacitor rated at 1650uF, 16V. After looking through my pile of dead electronic stuff, I failed to find another similarly rated capacitor at 16V or higher.
However I'm thinking of creating a combination of 1650uF with a 1000uF and a 650uF, both of which I have.
Now, according to textbook theory, when capacitors are placed in parallel, C(total)=C1+C2+C3...
I'm thinking of soldering on two insulated wires in place of the dead cap, and soldering in the two caps in parallel and insulating the leads off.
Would this...
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