stryd_one Posted May 8, 2008 Report Share Posted May 8, 2008 According to that schem, the elkos should have the positive terminal at the bottom, you've got them backwards...http://www.midibox.org/dokuwiki/bipolar_12v_psu Second schem right? Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 maybe he is the responsible person :D 8) Quote Link to comment Share on other sites More sharing options...
stryd_one Posted May 8, 2008 Report Share Posted May 8, 2008 damn metalheadz ;) Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 @stryde_oneyes they are ... the - lines of the elkos are below, so the + side should be on the top ... i think that ist ok. all elkos are build the same direction Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 äääähmmm at the bottom ... i thought the strong lines in the scheme were the - of the elkos :D Quote Link to comment Share on other sites More sharing options...
stryd_one Posted May 8, 2008 Report Share Posted May 8, 2008 Well I wasn't 100% sure myself so I googled it and...yep, they're backwards ;) Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 waaa thanks that is a great tip! but watching at this wikipedia pic it shows that the strong line in schemes is the - of the elko ... also on the prebuild boards of smash tv ... so if you say i should turn all 4 elkos i will do that but i cannot believe :o Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 ps: the view of the pic of the wireing is turned around! so it's exactly mirrored to the upper view. the - o the elkos show alwas in the direction of the 79 ... Quote Link to comment Share on other sites More sharing options...
stryd_one Posted May 8, 2008 Report Share Posted May 8, 2008 Yeh, when I look at the schem and how it should work, I'd say that the - of the elko should be on the bottom, so they aren't backwards...I dunno man, I give up. Told you that the bipolar transformer was the way to go ;) Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 :o :D ??? ::) 8)puh ... so i'm glad that i'm not the only one not having an idea what the problm can be :)i guess i'll rebuild the hole circuit a third time and then with the rectifier and a dual transformer ... hoping that solves the problem ... but thanks for the try! i was real getting mad about that :-X Quote Link to comment Share on other sites More sharing options...
nILS Posted May 8, 2008 Report Share Posted May 8, 2008 Amazing how this pretty simple circuit tends to mess with people all the time :-) Let's hope your third build will work!(Maybe someone needs to write a step-by-step 100% foolproof tutorial on that one [not gonna be me]) :D Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 hehei hope the rest of the fm construction won't cause such problems for me :O Quote Link to comment Share on other sites More sharing options...
stryd_one Posted May 8, 2008 Report Share Posted May 8, 2008 Amazing how this pretty simple circuit tends to mess with people all the time :-) Who else has tried this design before?(Maybe someone needs to write a step-by-step 100% foolproof tutorial on that one [not gonna be me]) :Dwhen it comes to the bipolar transformer, it's hard to go past northernlightx's thread... Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 heheit's me again :D10x 7912 and a few hours later i have built the circuit with two transformers and a rectifier after it .... the problem is still the same the 7912 gives me -17-18V maybe reichelt and hartnagel electronics haven't sold the best ones+12v does work as in the first onesi'll check the hole circuit in the next few days and hope it'll be just human missunderstanding but for today i 'ts enough :o ::) 8) Quote Link to comment Share on other sites More sharing options...
nILS Posted May 8, 2008 Report Share Posted May 8, 2008 [ x ] got pictures? Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 looking from top the upper one is the 7812 the lower 7912 sry for bad quality of the picture 8) ::) :P Quote Link to comment Share on other sites More sharing options...
minya Posted May 8, 2008 Author Report Share Posted May 8, 2008 can the elko caps be too big with 2200uF for double transformer version and 4400 uF for single transformer version Quote Link to comment Share on other sites More sharing options...
Marxon Posted February 8, 2013 Report Share Posted February 8, 2013 Hi all, i digged out this old topic because i had the same problem. There was -17V on the 7912 output. Finally it turns out that it was increasing to -12V on load. Maybe this info is usefull for somebody else. Marxon Quote Link to comment Share on other sites More sharing options...
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