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Help with a UPS circuit

Discussion in 'General Electronics Discussion' started by generaluser, Jun 19, 2012.

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  1. generaluser


    Jun 19, 2012
    I have a UPS which is having the problem that it even starts its inverter even when there is electricity (no loadshedding). The UPS is in charging mode but suddenly switches to inverter mode repeatidly for few seconds and stops charging then again switches to Charging mode and back again. This cycle goes on for many times. I have contacted some mechanics which say that i have to replace the entire circuit kit. Can you please tell me what can be possibly wrong with this circuit?

    IMO: I think the relays have gone bad but it appears that there are two relays of the cicruit. I have posted the picture of the ciccuit please help me detect the problem?

  2. CocaCola


    Apr 7, 2012
    Near the clear damaged and repaired area under the relay, on the very bottom trace hooked to the "OUT" screw terminal is that oxidation or the trace flaked away? Have you checked continuity in that entire area, to verify the repairs restored everything properly?
  3. duke37


    Jan 9, 2011
    That light blue furry thing to the left of the relay looks interesting!
  4. generaluser


    Jun 19, 2012
    Yes what is this relay? and what is its function? on its surface JQC-3Fc(T73)DC12v is written. Searching the net shows this data sheet for this relay. There are two relays on this circuit i can understand that one relay would be needed for the changeover from mains to ups voltage but i cannot understand why there need to be two relays?

    @Cocacola Thankyou for replying. I will check continuity and post the result here.

    NB: This is my first electronic project so i am totally new to all this stuff.
  5. Hanward


    Jun 19, 2012
    Your PCB looks not so'd better use HASL finishing.
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