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Barco 700 SF fault

Discussion in 'Projectors, Screens & Video Processors' started by JMPremier, Sep 3, 2004.

  1. JMPremier

    JMPremier
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    hello i hope someone can help me
    i have just got hold of a barcovision 700 but there seams to be a faulty
    the leds on the front show this

    coinc - amber
    hold down hd - off
    sf - red
    hold down eht - red
    standby - off
    -17v - green
    +hthd - green
    +conv - green
    +210v - green
    -9v - green
    +30v - green
    +9v - green
    +17v - green
    -conv - green

    from what i have read - by roland i think - it might be a voltage reg that is low that causes the sf fault which in turn puts a fault on the hold down ht

    or is it a ht fault that causes the sf fault?

    any pointers would be really welcome

    john

    ps i am an electronic engineer
     
  2. Roland @ B4

    Roland @ B4
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    SF = SCAN FAIL ie the circuits that make the beam sweep from side to side have gone faulty.
    The scan fail circuit tracks across several boards and connectors so that if one is faulty it will shut the pJ down.
    I suspect you have a faulty Horizontal or Vertical scan board.
    Do a quick check on the safty resistors on those boards (marked "SR")
     
  3. JMPremier

    JMPremier
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    hi roland
    i have checked the 2 (i can only find 2) safety resistors on the convergence board (part# 76020152(is that the scan board)) and they are both fine

    i did find some sort of fluid on the main psu in the section that has the eht xformer
    the fluid was very conductive too i have cleaned it all off with ipa buy now
    wonder if it was actually this fluid that has caused some of the the transistors or
    ic's to fail
    i will try to check them all but i will only be able to check the hi/lo resistance
    across the junctions of the transistors because i have no schematic to test for
    correct voltages
    i can test the 4093 with my ic tester

    do you think it might be in need of a new psu board? (part # 7622001)
    are they available or expensive?
    john
     
  4. Roland @ B4

    Roland @ B4
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    It's possible and yes they are expensive. though because you have all the voltage lights up I would be surprized if it is the PSU.
     
  5. JMPremier

    JMPremier
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    right i've got a bit further on this
    i managed to get hold of a 701s service manual (most of the circuit is the same) there doesnt seem to be a sf fault it looks more like a problem around the hef4093b also there is a transistor on the psu/ht board (q203/bc338) that is also faulty pulling down the sf signal from the deflection board
    what is also happening though is that one of pins 10 12 or 13 of the 4093 are also pulling pin 6 low (sf pulls pin 6 low for the logic to cut the eht on sf fault)
    i've unplugged the eht supply so that i dont damage the phosphors just in case i'm wrong about the scan circuit being ok
     
  6. JMPremier

    JMPremier
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    @roland
    should the horizontal and vertical deflection circuits still try to scan with the sf and eht hold down present?
     
  7. JMPremier

    JMPremier
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    update.......
    replaced q203 and hef4093 :) the sf fault has dissappeared and the hold down eht has cleared too :D
    but there is still a fault :(
    the fuse for the quadrupler was o/c so i replaced it, i have +300v going to the 'high' side of the quad primary but the 'low' side isnt being switched low for some reason
    it looks like i need to spend a bit more time on it but its looking promising
     
  8. JMPremier

    JMPremier
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    i think the quadrupler may be goosed
    the circuit now seems to be running ok but it pops the fuse for the quadrupler
    the peculiar thing is that all of the ic's throughout the pj seem to be dated 92xx and also on the plate the pj was manufactured in 1992 but on the quadrupler the date is mid 1993 which suggests that it has been replaced
    the pj has had hardly any use though (no dust build up and tubes look brand new)

    how can i test the quadrupler?
    how much are replacement ones?

    any help appreciated


    :oops: edit......
    the quad is the original i've just noticed the serial number sticker that matches all the other parts and the ser# on the plate too
    it is dated jan1993 i thought it said jun1993

    the part# for the quadrupler is R7622091 which is the same as the BG/BD701/701s and BG/BD808/808s so i expect there are many used ones out there........ anyone got one for a reasonable price? :lease:
     
  9. JMPremier

    JMPremier
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    Right a bit of good news, the quadrupler appears to be ok.
    I traced the fault down to the MOSFET that does the high speed switching for the quad, unfortunately I could not get one today that was the same (cant find the IXTH11N100 that it shows in the manual or the APT100R1BN that was actually fitted) the best that I could get was one that was pretty much on the borderline of being able to do the job (BUZ323) I put it in and hey presto the pj burst into life :) for about a minute before the BUZ323 died :(
    So at least I am now confident that it is repairable I just need to source the right MOSFET
    @Roland
    do you have any MOSFETs for sale? or what would you recommend as a replacement?

    John
     
  10. JMPremier

    JMPremier
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    Well its all up and running again, I replaced the MOSFET with a more suitable (more suitable than than the last one I fitted anyhow) 600v 20A device (IXFH6N100).
    I did a quick setup it took about 30 minutes so I know things will need doing properly, When doing the raster positioning on the blue and red guns they are both slightly out of the phosphor and I could only move the raster up and down and not left or right, the left and right keys just moved it up and down, am I doing something wrong or is there a logic problem on the convergence board or something?
    Also the image size was a bit 'jumpy' going slightly smaller depending on the overall light output of the pj, any ideas what causes this? is it due to the eht voltage being low or something?
    Any advice appreciated.

    John
     
  11. Roland @ B4

    Roland @ B4
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    John
    (When can you start £££££)
    Well done on the repair BTH.
    I have a IXTH11N100 here if you need it.
    Course L/R raster shift for R/B is on the underside of the focus/shift board. Two brass topped pots.
    Image width on one of these should be rock solid. so it could be your mosfet is underrated.
     
  12. JMPremier

    JMPremier
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    You have PM roland :)
     

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