I am trying to repair a Toshiba SD-3900 DVD Player. Power light (on/ standby) light comes one when depressed; LED panel never lights up and none of the functions work. Power supply appears to be okay. Any suggestions?
Earlier Tosh's used to suffer quite badly from short circuit electrolytics that served as decouplers on the + / - 12v rails. Probably worth running a meter over them all just in case. Failing that turning up anything, I would chase it from the angle of the VFD not lighting.
Arfa
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I checked the DVD player, both with the power supply board connected and disconnected, and the + and -12 volts are missing. I checked all caps on my Sencore checker and found 3 that may be bad (they are 25v or higher). They show up as bad on the dielectric absorption setting, which I have not had on previous checkers. I am used to finding bad ones either through leakage or the ESR reading. I am going to replace these and see what happens. Obviously the 12 volt rails are missing right off of the switching power supply. Thanks for your help, and feel free to add any more comments.
I checked the DVD player, both with the power supply board connected and disconnected, and the + and -12 volts are missing. I checked all caps on my Sencore checker and found 3 that may be bad (they are 25v or higher). They show up as bad on the dielectric absorption setting, which I have not had on previous checkers. I am used to finding bad ones either through leakage or the ESR reading. I am going to replace these and see what happens. Obviously the 12 volt rails are missing right off of the switching power supply. Thanks for your help, and feel free to add any more comments.
It's a bit odd that both rails are actually missing right off the power supply itself, if all of the other rails are there ok. I take it this particular model does actually use + / - 12v supplies ? Are the output voltages marked on the board ? Are you able to follow the output pins that should carry these rails, back to their origin ? Usually, there is just a winding on the switching transformer, which feeds a pair of Schottky diodes to develop the basic + / - rails. There is then just a series choke and a cap on each rail.
I tried looking on the Tosh European engineer's support site, but this model is not listed, so unfortunately, I was not able to download a set of schematics for it. I would be interested to know how you get on with this problem.
Arfa
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