Author Topic: Power Supply Repair Help  (Read 1698 times)

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Offline Stephenniall

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Power Supply Repair Help
« on: February 21, 2013, 01:23:32 AM »
Hi !

I'm looking for a little bit of help with a repair. I bought two of these power supplies off E-Bay a while ago for the massive sum of £10, And one of them has developed a fault in the last week.

It was working fine one day, Then the next day when i powered it up all the relay started to click erratically, and the voltage kept fluctuating up to around 20 volts. This power supply is a dual supply, so has two power boards inside, One per rail (Is rail the correct word?).

The relay wasn't clicking on one rail, so I'm guessing it was just this board that's broken. I've took the board out for a look, The power supply uses four 2N3055 transistors for the main power, I don't know the make of the supply, all i know is it is a model LC-1522, And was sold bu SJ Electronics here in England, It was an ex College power supply so has probably been battered all its life by college students.

I'm not too sure on what the relay does, Somebody told me it's to switch the mains transformer taps to different voltages, which seems appropriate...

Does anybody have any ideas on how to troubleshoot this, Should i replace the relay, or do you guys think it's something else ?

Please excuse my bad pictures, They were took with my phone !

This is the front of the unit



This is the Inside.


This is how it attaches to the transistors, The two boards are screwed on with solder tabs, and the whole assembly is slid into the power supply (I think its a rather neat design).


This is the top of the broken board


And the relay


And finally a picture of the bodge job done on the back, and all the flux residue!


Thanks alot for looking, Hopefully i can have the unit working again soon.

EDIT: It seems the forum has cut off some of my pictures, to see the full pictures you can click on my photobucket.
http://s1081.beta.photobucket.com/user/Stephen-Niall/library/Power%20Supply

Many Thanks,

Stephen.
« Last Edit: February 21, 2013, 01:26:04 AM by Stephenniall »
 

Offline Psi

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Re: Power Supply Repair Help
« Reply #1 on: February 21, 2013, 08:04:24 AM »
Then the next day when i powered it up all the relay started to click erratically, and the voltage kept fluctuating up to around 20 volts.

This could mean that one of the switches on the front panel is bad, or maybe a one of the pots is dirty and intermittent.
Greek letter 'Psi' (not Pounds per Square Inch)
 

Offline Stephenniall

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  • Posts: 30
Re: Power Supply Repair Help
« Reply #2 on: February 21, 2013, 08:49:44 AM »
That's actually something rather simple which I've overlooked, I've just checked the resistance of the potentiometers and they seem fine. I'll give them a clean tomorrow and see if that solves the problem.

Thanks,

Stephen.
 


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