Was it Faasse, P.R. who wrote on Thursday 19 September 2002 10:48: > 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 :-)
Yep, I'll go with that. >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. I gather you share my hesitation just to plug in another psu > > You *might* burn something on the mainboard that way, but the chances of > that i would not guess to be that high. I'll take my chances here :). I kind of know what I'm doing there. Divide and conquer. 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. I'd like to find that..... > > 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... Funny, I thought the peripherals could be checked easier and would have gone there first, trying to get a feel for the damage. If the disks are blown away, I won't give much fot the m/bs chances > > 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.. ELCO? Are we talking about output capacitors and ESR? I didn't get this. > > 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. That's fine - It's the lousiest m/b ever - SiS 5513/5591 & with onboard SiS 6326. Lovely bios - shame about the rest of it. I'll gladly sling it and buy new. I don't care if it dies - it's function in life was to keep my kids off MY pc. The only 'important' things on that were mp3s of 'music' lacking finesse, and games > > 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. > 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). -- 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).
