Wednesday, November 11, 2015

Sansui DVD player dead

Hi Humphrey.
I hope you well, I am busy repairing a Sansui DVD. I have scanned all the components looking for bad components, but there is no bad components.

I have checked the safety components of the primary circuit of this DVD everything is ok. I took my multitester meter checking for output voltage.

I found that the output voltage has dropped down. I tried to directly replace capacitors, but there is no improvement.

I have tried to locate the fault. I found that the output voltage has dropped from the secondary output diode. It uses ultra - superfast rectifier (SFF1004G). 

I could not replace this rectifier, because it is not available in the electronics shop. The only rectifier I can get is SFF1005G. I actually wanted to know that, can I replace SFF1004G with SFF1005G.

This diode has tested ok, now I am not sure whether it fails under operation.

Your help will be appreciated.
Regards,
Mbhekeni Magugu
South Africa


Hi Mr Magugu,
Usually all diodes used on secondary side are fast recovery diodes and therefore you can use (replace) with. Example the ones used to filter secondary sources.


You have said you tested the diode and you found it okay, therefore I advise you to trust your meter, that is the eyes of the technician.

Still at that you also said that the voltage is dropping immediately after the diode... Here is the catch... If the voltage drops after the diode means there is a shorted component on that line after the diode.

Just follow that line looking for any shorted components. The likely components to short are zener diodes, transistors, capacitors.
All the best
Regards Humphrey

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2 comments:

  1. Hi Humphrey

    My customer has a Pioneer DV-383 DVD Player.
    It plays all CD's perfectly, but for DVD's it either cannot identify, or may begin to play a DVD, and then after a few seconds, freezes and displays the exact second of the problem.
    Only a power down will enable the display to be cleared.

    All secondary PSU voltages are perfect. I replaced the Opto-Isolator and KA431 just to be sure, anyway - no improvement.
    ESR of all capacitors on both the PSU PCB and DVD Control PCB are fine.

    I reflowed the IC's on the DVD Control PCB.

    I then tested the laser voltages.
    According to the Service Manual, voltage above 0.4VDC is considered to be suspect, and requires replacement of the laser mechanism.
    The CD voltage is 0.15V, and the DVD voltage is 0.28V, so both are within limits.

    Have you any hints for this?

    Menahem Yachad
    Jerusalem, Israel

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    Replies
    1. HI Menahem, Thanks for your question and glad to hear from Jerusaleem, I suggest you change the laser directly, again be sure the pick rail is firm so that the lens moved smoothly.
      Regards Humphrey

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