Need Help to Identify Shorting Components in Powersupply

If it were me, then I'd have picked up the phone and rung the equipment manufacturer first. Then, I'm funny that way.

Whatever you decide to do to fix it, don't send it to Lokeshloki!

It is very much the case of comparing the components with the circuit diagram; if one is not to hand, then contact the manufacturer to obtain a copy. Work backwards through the circuit, replacing the last components first.

It sounds as though an output fuse would be a good last-resort improvement.

Thanks.

I was just randomly searching for faulty ones . Good i will work backwards.

It is only necessary to post in one forum. To make multiple postings on the same topic runs contrary to CR4 Rules.

I thought posting it in different section would help me get more views thats why i posted it in Instrumenttion and Electrical. This will not be repeated in future sorry .

Make changes to the following instructions depending on circumstances/available equipment.

Get a bench power supply set it to 100 mV 500mA (max)

Get a DVM with a good low voltage range: I've got a cheap one here with a 200 mV range.

Connect the power supply between the two shorted nets and turn on.

Use the DVM to "follow" the voltage "up" from the low connection point as far as you can.

Use the DVM to follow the voltage down from the high connection point.

Hopefully you will have ended up at two points either side of the faulty component or at a track short (what I used to use this technique for).

This is a tough one, depending on what you shorted and the type of power supply design (I am assuming it is a computer switch mode power supply complete with control integrated circuits) chances are multiple components were damaged.

If this is a computer switch mode power supply then it is almost certainly dead. These things are designed to the lowest cost and have limited protection against damage when used outside a computer.

If this is a simpler low component linear power supply you may be able to obtain or draw out the circuit diagram and locate the problem.

If however this is a complex or special custom board you likely wont be able to even get the circuit diagram (proprietary supplier information) making fault finding almost impossible. Integrated circuits for example will likely have their markings rubbed off and surface mount devices likely aren't marked at all.

A call to the manufacturer (or possibly supplier) is probably your best bet if the power supply is relatively expensive (above say $500 USD). If the power supply is cheap, sorry it will likely need to be replaced. Beyond economical repair.

What's the power supply anyway, can you post a photo of the front and back of the circuit board (that would really help)?

You always have a choice:

Physically, depending on your own wear and tear status, you could use:

1. A good light and a magnifier glass to make a visual inspection.

2. Assisted with a close nose sniff to localize the burnt or burnt out spots.

There might be a possibility that you see, recall and/or remember the shortened pins.

Locating these in the diagram might help you understand where the accident happened and lead you to the cause.

Depending on what you shortened, it might have just ruined part of the power supply or some semiconductor regulation of switching gear.

Check first the fuses. Smart designs are made to make these blow first.

You have identified the two pins you shorted, I assume. Simply attach the leads to those pins again, submerse the device in ferro-fluid and power up the pins. 120V at 15 AMPS should do it.The fluid will dance and bubble at the ruptured component.

Too right! I would add that the two shorted pins could be restored to their original length using a cold solder joint apparatus.

If the power board has a part number, google it on the internet "+schematic". You might get lucky. Unless it is a very simple circuit, it's very hard to figure out the circuit from looking at the circuit board. Try googling part numbers on any ICs or discrete components (transistors or regulator chips that look like transistors).

A wild guess is that you shorted the 5 volt output, and there might be a 7805 regulator or an output transistor burned out.

It's really hard to be helpful without more information.

Power supplies are the most unforgiving circuits to be attemted by a newbie. Get it fixed through an experienced tech.

Gajanan Phadte

As someone mentioned, searching for the failure yourself could be dangerous......

For that reason, I build my power supplies from an Elektor magazine design from 2003.

Most of the clever stuff is done in two big chips. Its short circuit proof, overheating proof, very efficient and can be made to run from mains voltage and have a DC output between 2 and 50 volts (from memory) at up to 10 amps.

It also has an output so clean that you can use it for amplifier usage. It was originally designed for a really top of the line DIY HiFi system from Elektor.....they are clever people!!

As you will have to build it yourself and obtain all the components, IF it ever does fail, you will KNOW what to replace.....its best safety aspect is that you must use a transformer at the front end, which a) reduces the AC to a less painful level b) isolates you completely from the mains.

Otherwise, it works similar to a SMPS, but safer!!

I prefer SMPSs, but they are terrible to fix for any amateur. They are also dangerous to life and limb during the repair process!! I would generally throw a defective one away and buy secondhand on ebay.....that was till I found the Elektor circuit!

But I have now built several over the years, not just for myself, I add a few tiny fans to remove any heat, and none have been damaged up to now!! I forget how many in total, but probably around 8 or so, plus friends have made heir own....

If that is interesting for you, send me a PM with a normal email address and I will send you a copy of the pdf. No cost....

If anyone else is interested, just send me a PM and a email address as well.....