Fluctuating Voltages across PS!

[Onyxx]

Hi guys, quick question; If you grab a volt meter and measure the DC voltage across the main cap (and other components as well) on the power supply from a DVD player and you see that the voltage goes back and forth from a few volts up to 300+ volts continuously (AC line here is 220), what do you suspect? Where do you look first?

I have checked all the components but failed to find anything wrong. I am a beginner and this goes beyond my experience, I guess. If someone can point me in the right direction I will appreciate it!!!

Thank you!

 

[Resqueline]

There's not much between the AC and the cap. A filter and a rectifier is just about it.
Measuring the AC & the DC at the rectifier should indicate wether this is faulty.
I guess the DVD doesn't work very well and that you have no reason to suspect the meter is flakey.

 

[Onyxx]

Thanks Resqueline,

Yes, the dvd player does not even turn on and no, no reason to suspect the meter. The diodes on the rectifier measure OK but I will go ahead and change them anyway, mainly because I am not sure how to test them on a live circuit.


Thanks again!


Anyone else with ANY suggestions at all???

 

[sheldonstv]

can you either post a picture of the powersupply used or give the model nr of yr dvd player so i can have a look at the service manual????

 

[Onyxx]

Hello sheldonstv, thanks for your support. Here is the info you requested as it is printed on the PCB it self:

MIZUDA REV:1.0A Power Supply Model: ST-11B. PBC
P/N:20040907


I decided that the rectifying diodes are Ok so I did not change them. However, I am suspicious of the chopper transformer. My question is; is it possible for a bad chopper t. to cause the symptoms described above?


Thank you sheldonstv and anyone else who jumps in!

 

[Onyxx]

Sorry sheldondstv, I missunderstood your request. Here is the info for the DVD player it self:

Brand: HYPSON
Model (as far as I can tell): DVD-P306.

Hope this helps and thanks again!!!