power supply REPAIR info

I am looking for info from people who REPAIR power supplies (as distinct from just replacing them.) What are the most common repairable difficulties? I am looking for details and for statistics to help me rank the most common problems. I will give points to more than one respondant. (The question is not really hard but the answer could be time consuming.)
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aburrAsked:
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jhanceConnect With a Mentor Commented:
Based on personal experience, I'd say the #1 problem is cooling fan failure.

I'll have to admit that I have replaced or repaired the fans in PC power supplies but it was to save a trip to the PC parts store when I was in a hurry.  Normally, I'd just trash it and get a new one.
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jhanceCommented:
I assume you are talking about PC power supplies.

If so, then there is not a viable business repairing these things.  There are several problems, some technical, others economic:

1) There are MANY manufacturers of PC power supplies, many in Asia.  While these are standard on the outside, the innards are just about anyones guess and designs change all the time.  There is little if any repair information availble.

2) Many if not all the parts used in these things are "house" brand parts.  That is they cannot be purchased by a repair shop and often cannot even be clearly identified for a cross-reference.  This makes for a difficult repair.

3) The cost of NEW power supplies for repair use in systems is very LOW.  Since you can but qty. 1 of these things in the US$30 (or even less) range, the volume cost is probably under US$15.  If a repair technician spent even 30 minutes working on one of these (assuming he could get the parts to fix it) it would cost more just in labor than to just buy a new one.
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oldgreyguyCommented:
to Jhances point, repair of PC powersupplies is a lose lose proposition. The PCB board inside can be manufactured for 3.5 USD............. the fan can be purchased in volume for 70 cents.............. hell the powersupply is only good for recycling the metal case.



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OttaCommented:
> Based on personal experience, I'd say the #1 problem is cooling fan failure.

Agree, 80% -- the other 20% is "excessive-noise" from a still-working fan in a 5-year-old (or more) power-supply.
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dbruntonCommented:
It's probably cheaper to buy a new case with a power supply in it than try and get a power supply by itself.
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newwaveproCommented:
#2 failure is a simple blown fuse... I have opened and repair several PS for just in shop work and to give younger tech's the looks at a PS, but most of them should learn this in a advance hardware class in college or A+ (if they still teach that anymore)  But then again I took the classes based on old 8088 standards, and PS's were very simple back then but the essential design has not changed.

Other factor is that most of them are rivoted together so that you are unable to take them apart.  The business has shifted to the throw-away and buy new theory.  

We did though in the past open them up and replace them "before the stricter EMI (electro-magentic interference)" standards took effect.

So to really undertake this project consider the costs

your time vs money on buy and replace. Your Call

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aburrAuthor Commented:
Thanks for the fan and fuse info.

The point of just replacing the PS (and I was thinking of PC PS) is well taken, but I need the info for use in third world countries where power supplies are not easily available and import duties changes the economics considerably. The points on proprietary and unlabled parts and the wide variety of designs are worthwhile to me. Am I correct in thinking that by far the most common circuit now is some type of switching power supply?
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jhanceCommented:
>>Am I correct in thinking that by far the most common circuit now is some type
of switching power supply?

I don't think I've ever seen a PC power supply that was NOT of the switching type.
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Ryan RowleyCommented:
I have repaired a few powersupplies before.. More being just board than anything else.
Dirt and gunk causes more damage to electronics than anything else.  I make it a point
to periodically take apart my computers and other electronics, including breaking down the
powersupply.  I clean all the insides completely. Make them look brand new.. I have some
that are almost 20 years old and work perfect.  

What I see in PS's is the effect of dirt and the heat that builds up do to the dirt.  
This causes shorts and small electrical fires that burn up components.
The small fan motor is very delicate and sensitive as well.  Fan motors are cheap
and easy to replace..  Sometimes just cleaning a PS will get it up and running.

The top three items to break down in Powersupplies are:

    1.  Fan - easy to replace
    2.  Power regulation electronics. - May be easy but don't count on it - parts,parts,parts
    3. Transformer - Easy to replace if you find one that matches.

It is more economical to replace a PS than repair it.. The better choice might be to keep your stuff
clean... Lot less failures that way...  Also a good surge suppressor will handle the other form of
damage..





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aburrAuthor Commented:
Answered question and gave helpful info
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