Hello Declan, You mention an ATX supply, so i'll assume that the whole rest of the system is not too antique...
It definitely looks like you have a spare ATX connector :-) You could cut it loose from the ATX supply, look up the specs for the voltages -> pins of the ATX supply output and then go to work on the mainboard. Remove all that you can from the PC (video card -if there-, other I/O boards, CPU, memory, disks, whatever else is connected to the supply :-) and then try to supply each of the board's voltages with the lab-supply you mentioned and the ATX connector. You *might* burn something on the mainboard that way, but the chances of that i would not guess to be that high. Besides, you just removed all 'salvageables' from the system :-) If any of the 5.0V, or 3.3V voltages are shorted: despair. These voltages are used all over the board, and you'll have a ball finding out which of the chips has burned, not to speak of any attempts to replace them (have you ever replaced ball-grid chips with d.i.y. means? I tried and fried the result... you can't really see *what* you have just interconnected). The + or - 12 Volts are usually only used for the RS232 buffer chips and perhaps a few other places (CPU 'internal' 2.0 .. 3.5 Volts supply), so if they short there is hope yet. NB: a ATX supply needs to be 'switched on' from a signal on the board. You might well find that the 5.0 V will draw ~0.0 mA because the 'switch' signal is not on. There ususally is a jumper connection of the board that must be shorted for a moment to switch 'on' the supply. Another note: when the 12V and 5V are ok, you should have a look at the CPU voltage(s): they are usually made from the 5 V and/or 12 V, and these modern s/m 5.0 -> 2.0 .. 3.5 Volts converters are ticklish... Not so difficult to analyse (AD1148 controller chip + a few mosfets), and usually quite possible to repair. If you get through that, then you can start trying the I/O, disk etc... NB: Thing just might be less grim than they look: If one of the secondary elco's blew when you switched the thing on, then that may well be because it got the heat when power was drawn from the supply. In my experience burned elco's are the #2 reason for defect s/m power supplies. Elco's seem to be designed for 50 Hz recification, and the >40 kHz may well make them develop 'series resistance'. When the power drawn from the supply goes up, then the dissipation in this 'series resistance' goes up, and your nice explosion could well be the result. One more reason to mistrust ATX supplies is that they keep the supply 'dormant' all the time instead of really taking the power off. The dormant state means that the s/m part of the supply keeps working, and banging on the elco's. I have developed the parctise of putting 1.0 or 2.2 uF non-electrolytic capacitors in parallel to the output elco's of any s/m supply that i am fond of. The non-elco capacitors 'eat' the high-frequency currents, so that the elco's can do the low-frequency filtering without getting all of these high peak currents.. W.r.t. your PC: another matter is how much trust you will have in the components of a 'refurbished' PC should you get the thing on the road again... Some of the parts of the PC might well have gotten a 'kick' that brings them on the edge of breakdown, so they die on a quiet moment later on. hope it helps, Peter > -----Original Message----- > From: Declan Moriarty [mailto:[EMAIL PROTECTED]] > Sent: woensdag 18 september 2002 20:19 > To: Multiple recipients of list CHIPDIR-L > Subject: Best approach to a dead atx pc? > > > I powered up an atx pc here, which ran for three seconds > before there was a > LARGE flashand everything went quiet. > > Picking over the entrails of the psu, I find a capacitor case > (100uF 10V) > empty and loose. It apparently lived in the output area of > the power supply > on the low volts side. The fuse is vaporised. It looks grim - > like some HV > got accross. Capacitors don't normally do that! > > What's the best route now? The psu is toast - I'm wondering > about the m/b > and hesitant to slap another psu on it, as I have enough > toast. But it might > be OK, or some of it might. > > I have a lab supply here (2 x 30V 2.5A @ 1x5V 2.5A or 1-15V > 1A), a Signature > analyser even, but I'd like to hear opinions. How do you > trick an atx board > into life anyhow? > > -- > Regards, > > > Declan Moriarty > > > > > Applied Researches - Ireland's Foremost Electronic Hardware Genius > > A Slightly Serious(TM) Company > > Experience is like a comb, > that Life gives you - AFTER all your hair has fallen out! > -- > Author: Declan Moriarty > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB CHIPDIR-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > > -- Author: Faasse, P.R. 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