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Faulty power supply

Michael black

Jul 7, 2015
5
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Jul 7, 2015
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hi all bought a cople of power supplies of eBay (they were cheap honest) They both have the same fault that the voltage from the outputs don't match the marked voltage. This doesn't bother me too much I can use a multimeter to ensure I have the voltage required. The main problem is it's a 130 VA supply but at 12V and 2A the voltage drops off. Looking inside the power supply it's a transformer with 3 tappings and 4 relays change the voltage for the ac output, the DC output is a bridge rectifier straight from AC to DC.
The centre circle on the board is where the rotary switch goes.



image.jpeg image.jpeg image.jpeg what in the circuit can caus that fault
 

davenn

Moderator
Sep 5, 2009
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The orange wire on the left has broken off the PCB.

more precisely ... the orange wire on the left in the top photo

the one on the right in the bottom photo looks OK



Dave
 

Herschel Peeler

Feb 21, 2016
401
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Feb 21, 2016
Messages
401
hi all bought a cople of power supplies of eBay (they were cheap honest) They both have the same fault that the voltage from the outputs don't match the marked voltage. This doesn't bother me too much I can use a multimeter to ensure I have the voltage required. The main problem is it's a 130 VA supply but at 12V and 2A the voltage drops off. Looking inside the power supply it's a transformer with 3 tappings and 4 relays change the voltage for the ac output, the DC output is a bridge rectifier straight from AC to DC.
The centre circle on the board is where the rotary switch goes.



View attachment 28885 View attachment 28886 View attachment 28887 what in the circuit can caus that fault

I don't see the capability of 130 VA on that board. The TO-220 case in the lower left corner ... is it an LM317?
Otherwise a nice looking power supply.
 

Bluejets

Oct 5, 2014
5,994
Joined
Oct 5, 2014
Messages
5,994
  • A 240V input power supply with adjustable output in 1 volt increments
  • Output voltage variable by rotary control knob up to 13V
  • Continuously rated output of 8.5A, AC or DC

    Note on the bottom of the unit .......

    The internal transformer is protected by a thermal trip. This will not operate in normal use but should the instrument become excessively hot, the trip will temporarily cut-off the output.
Philip Harris model No. G83458
 

Michael black

Jul 7, 2015
5
Joined
Jul 7, 2015
Messages
5
Thanks for the replies guys the orange wire has been removed from the board to test its the thermal trip and is not open circuit. The supply works in a fashion boil won't give out the power it should. Any ideas?

Mick
 

Nemo1956

Sep 5, 2016
34
Joined
Sep 5, 2016
Messages
34
  • A 240V input power supply with adjustable output in 1 volt increments
  • Output voltage variable by rotary control knob up to 13V
  • Continuously rated output of 8.5A, AC or DC

    Note on the bottom of the unit .......

    The internal transformer is protected by a thermal trip. This will not operate in normal use but should the instrument become excessively hot, the trip will temporarily cut-off the output.
Philip Harris model No. G83458
Wow it goes to 13. I was under the impression they only go to 11.LOL
 

Nemo1956

Sep 5, 2016
34
Joined
Sep 5, 2016
Messages
34
Sorry but miss your point.
Spec says 13 and so does 2nd photo in post #1.
No this comment is really intended for an amplifier If you have seen the the film you would have understood the comment.
It'sjust for fun.
 
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