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Dual output PS 12/24v missing 12v output

born2fly

Dec 20, 2022
2
Joined
Dec 20, 2022
Messages
2
I cannot determine why there isn't 12v present anymore.

The schematic is not available, Hayward Industries. Voltage on main caps is 170v. I have replaced LM2596, 13NM60N, LM239, 1380D & both opto's. There is 9.35v present on the feedback terminal of the outermost opto, it should be 11+v. There is currently 1.5v on the 12v output. There is a 5 pin regulator marked fc406 that has 23+v on pin1(?) and only 9.35v on pin 3, that should have12v, I don't know what that component is, tried to locate it unsuccessfully.

The 24v is present, no issue. I do not know where the 12v originates from but have back tracked the 12v rail from the output and found all components to be ok except the 5 pin IC and the voltage out on LM2596 pins 2 & 4 is only 9.35v when it should be 12v. All thru hole components were removed and tested. Electro Caps were tested with ESR meter. This board is the victim of a lightning strike ESD, no visible damage. I've spent hours trying to find the fault but striking out on this one.
 

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kellys_eye

Jun 25, 2010
5,296
Joined
Jun 25, 2010
Messages
5,296
What are the current rating of the outputs? i.e. 12V and 24V?

Does the main switching transformer deliver the 'base' 24V and is the 12V derived by a simple regulator on the 24V line? or are they both separately derived sources i.e. from individual secondary windings on the switching transformer?
 

born2fly

Dec 20, 2022
2
Joined
Dec 20, 2022
Messages
2
What are the current rating of the outputs? i.e. 12V and 24V?

Does the main switching transformer deliver the 'base' 24V and is the 12V derived by a simple regulator on the 24V line? or are they both separately derived sources i.e. from individual secondary windings on the switching transformer?
24v comes from the transformer. 12v generated by buck converter circuit with feedback.
 
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