Thursday, 30 October 2014

Panasonic SA PT470 dead, no power.

A Panasonic home theatre system, passed to me as dead no power.

A close listen revealed that the unit was not totally dead, pressing the power button the unit would click on then immediately off (but nothing on the display). This could be repeated a second time but then the unit would not respond. Pulling the power lead would allow this sequence to be repeated.

So the unit was alive and intelligent.

A quick google gave me the manual to download from the excellent site, electrotanya.

http://elektrotanya.com/panasonic_sa-pt470.pdf/download.html

Panasonic / Technics manuals are absolutely superb.

I may do a post about my beautiful Technics SC-CH900 that I finally bought after 22 years ! :-)  anyway..


So I opened it up and stated to take a look. Nothing obvious so decided the best plan of attack was to take the PSU out to get some proper access.

Admission: I took a stonking 360v dc hit from the main cap, Warning,  always approach with caution, measure the high voltage DC caps, and discharge as appropriate.

This fault will leave the main caps charged. I usually check but got sloppy.


So nothing jumped out visually, the mains went through a hefty filter and feeds standby power section of the PSU, the main psu is switched in through a relay, the relay only stays in if the PSU behaves correctly.

I did some passive checking but again nothing jumping out.

A move not without risks but I decided the best way forwards was to bypass the relay and see what wasn't powering up, the brain was obviously not happy and shutting everything down.

Using the drawings I checked all the rails and found the 18v fan power to be absent. I checked the rectifier diode D5805 and found it short. Fitted a repalcement and all good.




10 comments:

  1. Hi i have the same fault, what is the spec of the diode? and where can i buy one? many thanks in advance. great blog!

    ReplyDelete
  2. Thanks for this post. I have the same issue and same question. Where can I get a replacement diode. It's marked as KS2102. Many thanks

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  3. May I just say that on the diagram the line pointing to the diode() is in fact pointing to three diode rectifiers that reside on the heatsink unit and are labled from d5801-3. The d5805 is a bigger diode that is next to it.

    I have the exact same simptom on mine but have found the d5801 two pin diode to be art fault and not the d5805. What I'm trying to say is is it possible that these two faults can cause the same symptoms as it would appear to be the case!!!

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  4. Yes my problem was the two pinned diode D5803 on the heat sink on the 18 volt line, great blog with great detail. Thank you and love the warning, those power caps do pack a punch!!

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    Replies
    1. Do somebody have a replacement found for the diode 5805 D0HFRJ000012?
      Regards Harold

      Delete
  5. I find the replace for any one needed FML-G12S

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  6. panasonic sa-btt270

    Could anyone help me please. Given a dead player and found that if I blew cold air into it from a hairdryer it would work perfectly. The fan was working but still gave a clean out. Has anyone got any ideas. Thanks in advance

    ReplyDelete
  7. panasonic sa-btt270

    Could anyone help me please. Given a dead player and found that if I blew cold air into it from a hairdryer it would work perfectly. The fan was working but still gave a clean out. Has anyone got any ideas. Thanks in advance

    ReplyDelete
  8. Just stumbled accross this pos and comments, i have similar issue and i've not been able to sort it out for 2 years plus now..The red dot light on the power button comes on but the system doesn't come on. Please can i get help here?

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  9. Hello Mr LowFinger, how do i get the component replacement (or equivalent) for D5801, D5802 or D5803, because i have same symptoms like that, after checking those diodes found out that actually D5801 was broken.
    When i check the Service Manual it said diode b0hbsm000043 which i cannot find this component on regular market.

    ReplyDelete