On 24 Apr 2004 at 1:39, Declan Moriarty wrote: > I have the repair job on 3 dc/dc converters, worth a lot, but very > awkward. They have a switched transformer feeding 3 further switched > stages (+24VDC in , +/- 15V out, &aux supply). Some problem fed 24V back > up a +15V line. I have removed all visible shorts and faults, and still > the input switched stage will not run, so the second 2 receive no power. > > I have 2 questions: > 1. Why - what's it thinking? How does it know the outside supply > is/was buggered? > > 2. Any ideas on this thing in the middle of this pcb. It looks > like a pcb 'sandwich transformer', and has loads of connections > off the pins underneath. The black part in the middle is ferrite > > http://homepage.ntlworld.ie/e-tronic.genius/smpsucard.jpg > > > TIA > -- > > With best Regards, > > > Declan Moriarty. > -- > Author: Declan Moriarty > INET: [EMAIL PROTECTED] > > Fat City Hosting, San Diego, California -- http://www.fatcity.com > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB CHIPDIR- L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing).
There must be at least one feet back, normally there are 2. The first will be the current measurment of the switching transistor, the second mostley comes from the secondary side, which is got to be isolated, the use opto's most of the time. Have you verified the switching cap to have low ESR ? I had experience with faulty switching transistors, which looked just fine to simple checks, but just did'nt work in this PWS anymore. Whenever I have opened a transformer of this kind, I have never found anything wrong, what doesn't mean it never happens to be. Does that switcher an atempt to run on power-on ? Cheers Friedel -- Author: Friedel Bruening INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
