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Need repair help with CP-RS55 Projector PSU

Discussion in 'Troubleshooting and Repair' started by karlfoxman, Feb 12, 2011.

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  1. karlfoxman

    karlfoxman

    11
    0
    Feb 12, 2011
    I have been working on this projector for a while now and its really stumping me!
    This is what it started doing;
    Turn on mains, blown fuse, bridge rectifier, MOSFET Q102, PNP Q103, Q104
    R103, R104, R105, R106. Output pin 7 IC101 (FA5501)

    Replaced all of these and tested using 12v-240v Inverter on current limit at 12v. Pulled 1A @12V off load.

    Now we had no problems but we cant see IC102 working, I believe its a FA5508. No datasheet! So I looked and found it had same pin outs as FA5542. But we tested voltage on Vcc of IC102, found 20v. Looking at datasheet for FA5542 the 20v comes from the internals of the IC and is picked up from pin 8 (VH) This is a voltage enabling the Mosfet Q201 to get the transformer T201 to produce the voltages for the rest of the PSU. I am really stuck with this problem now as all the parts we replaced do not make the PSU work. We get no outputs from any of the 'cold side' OF T201

    Attached is some datasheet for FA5542 (Closest I can find for FA5508)
    Also screenshot of Schematics for PSU

    Obviously the FA5501 (IC101) is not recieving Vcc as there is no 4.1v to pull up on/off pin of CN102 so the rectified mains is around 330v where it would be 370 if IC101 was working, the way I see it IC102 should power up first.

    Thanks in advance for any help.

    http://img10.imageshack.us/f/rs55psu.jpg/
    http://www.fujielectric.com/device/semi/products/ic/ac_dc_green.html
    Click on the FA5542 link pdf, near top page.
     
    Last edited: Feb 13, 2011
  2. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    I'm unable to open the full size picture of the diagram, and the slideshow mode doesn't seem to provide full resolution.
     
  3. davenn

    davenn Moderator

    13,552
    1,850
    Sep 5, 2009
    yeah likewise, and the small pic is not clear enough to read

    Dave
     
  4. karlfoxman

    karlfoxman

    11
    0
    Feb 12, 2011
  5. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Didn't you also replace Q101 & Q102? Did R102 survive? Did you check all diodes & everything else around, like D203 & R203? 20V should be enough to activate most IC's.
     
  6. karlfoxman

    karlfoxman

    11
    0
    Feb 12, 2011
    Sorry we did replace Q101 and also Q102, I believe R102 was ok after we checked it. We tested both doides D102, D103 and were ok. The IC201 uses pin 8 (VH) to start the Mosfet Q201 switching. Without the IC201 working not even IC101 will work, as you can see by the opto couplers with out a 4.1v supply the Vcc to IC101 is not there. I am closely looking into why IC201 is not working, I think we have found this area to be where to look.

    Also have checked to shorts on the T101 and measures 390uh, this is inline with the application notes on IC101.

    My thoughts are now conditions around IC201are not as they should be, either the IC is in some sort of shut down mode, safe mode or has completly failed.
     
  7. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Yes, it needs IC201 & power on the secondary side first in order to start up the power factor correction circuit (IC101). What about D203 & R203?
    Can you indicate where in the diagram the tracks burnt?
     
  8. karlfoxman

    karlfoxman

    11
    0
    Feb 12, 2011
    I will get the Zener looked at and also the resistor you mention, I will try to supply Vcc for IC101 externally to see if it will switch the fets and supply the 370v. At least that way we can focus on why IC201 is not working as it should do.

    Here is the best I can do with getting the burnt tracks on the schematic's.

    http://img207.imageshack.us/i/trackdamage.png/
     
  9. karlfoxman

    karlfoxman

    11
    0
    Feb 12, 2011
    Also if anyone can find a datasheet for FA5508 I would be very greatful!! I have looked everywhere!
     
  10. karlfoxman

    karlfoxman

    11
    0
    Feb 12, 2011
    Done some more fault finding, found datasheet for FA5518 which is equivilent of 5508. Measured voltages on PIN1 (CS) and gives reading of 8.7volts. Now reading the datasheet this indicates that the IC is in latch mode. Looking back at the schematics im thinking a condition on the CS pin is causing the latch.

    Can anyone think of a idea what CS pin is doing? I know that PC202 are doing and I believe PR101 is a therminstor.

    FA5518 Datasheet

    http://www.megaupload.com/?d=B1L2IYBS
     
    Last edited: Feb 16, 2011
  11. karlfoxman

    karlfoxman

    11
    0
    Feb 12, 2011
    Just to let you all know, its now 100% working. Found the faults, the psu testing lead us to believe was still problems as was not under any load. Gave Vcc low and very noisy readings with no loads on the outputs!
     
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