noobies99 Posted February 13, 2007 Report Share Posted February 13, 2007 sharp 20v-s300 model. no secondary output, transformer making a loud high pitch sound. Quote Link to comment Share on other sites More sharing options...
mvs sarma Posted February 13, 2007 Report Share Posted February 13, 2007 HiTry disconnect the load and give artificail load of say 1amp across 20V point and see-- load like 22 ohms 20 watts resistor BE VEY CAREFUL AND GUARD YOUR GOOD HEALTH-- THESE SMPSs are SHOCK prone. Quote Link to comment Share on other sites More sharing options...
noobies99 Posted February 14, 2007 Author Report Share Posted February 14, 2007 thank sarma. before i read your reply i already decided to remove the transformer(dont know what's the transformer of smps called?) to do some continuity testing only not check the resistance cause im not sure what is the usual resistance of each coil(what is the typical resistance of a coil? ) then i put it back in the board after checking for shorted pins and everything,i plug it and turn on the power botton. somethings happened, the fuse keeps bursting. i remove the transformer and turn it on again. the did not burst.i measure the resistance of the transformer. i found out that all the resistance of the coil is equal/greater than 0 but not greater than 1 ohms in all coils. I assumed that the transformer is shorted. is it? and if it is shorted why it creates a high pitch without bursting the fuse but after i remove it from the board and put it back without doing anything wrong the fuse start bursting? ??? Quote Link to comment Share on other sites More sharing options...
mvs sarma Posted February 14, 2007 Report Share Posted February 14, 2007 Hishould we now feel that the fuse is not blowing after second time soldering?coming to smps tranformers, the parameter to be checked is inuctance of the primary and secondary coils, turns ratio (Np and Ns, and cross insulation of secondary wrt primary. as you switch the rectified DC using a high frequency of the order of Few KHz, DC coil resistance has no relevance. some times when operating frequency goes to few hundreds of KHZ, turns come down to 20etc, and windings will be paralleled in order to increase cureent carrying capacity.i was asking you to test smps exclusively with an artificial load, say two 12Volt bulbs, in series to make 24 volts .or a resistor as i suggested, mean time you can check for vertical section driver IC or final stage transistors, anf the final transistorof line output for short. Quote Link to comment Share on other sites More sharing options...
noobies99 Posted February 17, 2007 Author Report Share Posted February 17, 2007 thanks again sarma. i disconected all the load in the output leaving all secondary pins hang. but still the fuse blown. do i need to put load to prevent the fuse being busted? Quote Link to comment Share on other sites More sharing options...
mvs sarma Posted February 18, 2007 Report Share Posted February 18, 2007 Hi,i didn'tmean disconnect all sec connectios of smps tfmr. i only said that the load , i mean, the DC load on 20V output-- if there is a short in the load , this type of sound comes. I was asking you to test smps exclusively with an artificial load, say two 12Volt bulbs, in series to make 24 volts .or a resistor as i suggested, Sarma Quote Link to comment Share on other sites More sharing options...
zander19 Posted June 26, 2010 Report Share Posted June 26, 2010 hi would you mind to check all secondary diodes??? sumtimes a shorted one is causing that problem ::) Quote Link to comment Share on other sites More sharing options...
indulis Posted July 1, 2010 Report Share Posted July 1, 2010 Without the transformer (if it Quote Link to comment Share on other sites More sharing options...
judaspriestcody Posted December 12, 2010 Report Share Posted December 12, 2010 i suggest test the h.o.t...i might be short...or check diode r2m...just try my suggestion Quote Link to comment Share on other sites More sharing options...
Stephenah Posted December 30, 2010 Report Share Posted December 30, 2010 hi would you mind to check all secondary diodes??? sumtimes a shorted one is causing that problem ::)this is a good advice. I have the same problem and I do take it for people's advice. good luck. Quote Link to comment Share on other sites More sharing options...
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