How to repair motherboard

[Guest]

how to repair smps

 

[jsc]

I'd say that unless you have a lot of electronics experience, don't try it.They have lethal voltages inside. They have special parts inside. Those aren't just regular transistors and diodes inside. And you cannot get schematics.

On the other hand, it already doesn't work. So you cannot mess it up worse than it already is.

No one repairs the small and medium sized PSU's. It's just not economical.

 

[belial2k]

not worth it...if its a newer MB it should still be under warranty...if its an older MB the parts will cost more than a replacement, and that doesn't even account for your time you spend figuring out what is wrong and tracking down the parts. Computer parts repair is really about computer parts replacement.

 

[RetiredChief]

A couple of problems with repairing MBs.

(1) Very few have the test equipment needed to isolated the defective part and as jsc pointed out you will generally need a schematic.

(2) Most likely, more than one part will be defective. If you find a blown resistor - What caused it to blow. Same for diodes and transistors.

(3) MBs are multilayered which means unsoldering and soldering can be tricky. If defective part is a IC, it can be a real bear. You would normally just cut the IC out desolder each pin/pad trying not to destroy the trace/pad in the process. I'm trained for solering on flight hardware and I would not attempt replacing a IC at home.

jsc =- The only lethal voltages are in the PSU on the input side - ie the 120/240 VAC

 

[masterjaw]

Do yourself a big favor and just buy a new mobo.

 

[Shadow703793]

@OP:
1. You ask for How to Repair motherboard on the title...

2. Then you ask how to repair Switching Mode Power Supply (SMPS = http://en.wikipedia.org/wiki/Switched-mode_power_supply ) in your post.....

so....

@RetierdChief:

jsc =- The only lethal voltages are in the PSU on the input side - ie the 120/240 VAC

What about the capacitors? Don't they have high voltage and capacitance?

 

[masterjaw]

^+1

IIRC, capacitors inside the PSU still have enough stored voltage to kill you even though the PSU is turned off.

 

[jsc]

Chief,
Yes, indeed. But they are still inside the PSU.

 

[RetiredChief]

-1 masterjaw
Reference capacitors charge. Computer PSU use a step down transformer. 120/240 VAC are only on the input side - NO 120/240 Volt high capacitence capacitors on input side. On secondary - low voltage (Max dc output is the +12V which the avg person would no even feel).

When measuring with power applied - remember the golden rule - key one hand in pocket - or only use one hand to make measurement and if possible attach meter probes with power off, turn power on, read, remove power.

I AGREE with jsc in pointing out the AC input. I've been hit by the 120VAC more times than I can count. >20Kv, only once, 1 Kv to 10KV a couple of times.

Respect the voltage, but do not be afraid of it.

 

[jsc]

I've been zapped by a 14 kv CRT power supply (low current). What really hurt was being bounced off the shop wall behind me.

john
retired Army radar tech

 

[RetiredChief]

jsc - retired AF weather maintence (taught 5 different radar systems)

2nd golden rule - never stand behind a tech working on a radar system. They had a student bury a screw driver in the wall behind him. I had one student get hit with the High voltage supply for a magnatron (old bomb-nav radar converted to ground based weather radar)- He learned to speak clearly after that. Had another student burn a hole in his finger.

most of my "contacts" were on the Old Tvs (25KV for a color CRT) and once I let my pinky get to close to the horizontal oscillator while tuning it - preachers house, so all I could say was ouch, other words were silent.

 

[obsidian86]

http://badcaps.net/

they should have a cap kit