Goodmorning sir, i have a little problem on one of our liebert emerson ups of 6kva, the problem is on the GATE DRIVE AND P.F.C. Please send me the equivalent of this component; UC3705N.This is the part number of the board,76275000, serial no.9341049.And also i have two resistors that burnt,so i don't know if is in ohms/kilo/meg.i will be grateful if i can have your contribution.thanks for co-operation.
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Hi, Thanks for contacting fixya. There could be many reasons.
1. The battery is old and completed its charge-discharge cycle.
2. The step down transformer (220/110V to 12/24V) coils got shorted inside.
3. For a trickle charger, the SCR might have gone bad.
Solution for 1. Take out the battery and charge it by another charger. You can use laptop charger, cell phone charger or any charger. You might have to do a little bit circuitry. Then after 2-3 hrs of charging see if the battery voltage goes to its peak. Use a voltmeter or multimeter to measure that. If the voltage does not goes to its peak then battery is faulty. And the charger circuit has no problem.
Solution for 2. Some times step down transformer goes wrong. Measure the output voltage by a multimeter and see if it is giving the voltage what it should be. If not then change the transformer.
Solution for 3. I don't know how to determine if an SCR is wrong. The easiest way to check is to replace it and see if the battery is changing.
Very complicated these items. I have not been able to repair even apparently simple faults, manufacturers such as emerson/leibert do not release cct diagrams, so very difficult to fix as there are many different sections (pfc,rectifier,charger,upconverter,bypass,inverter) of the circuit all interconnected with a micro processor monitoring and controllling the whole thing. You have to be really lucky to sort out any problem particulary one with blown components.
Try to find your manual here in this site. Choose your Product Category, Product Application, Application Type and Specific Product. After that you can download the manual. Hope this helps. "http://www.liebert.com/servicesupport_pages/ProductDocumentSelector.asp"