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Monitor CTX Model CGP1772E VL700 problem

15 Lut 2008 20:57 2045 3
  • Poziom 12  
    Hi all colleagues
    i have this monitor CTX Model : CGP1772E based on chassis VL700 , the green led is blinking too fast and i found the HOT Q403 = TT2054 was short circuit , tried to load the power supply with 60W light bulb while the HOT is out of circuit but now i see i have a power supply problem as will , the power attempt to start for a second and then shut down .
    the power supply is based on 3842 PSU IC and both of the two 56K in series startup resistors seems to be ok , one of them is slightly high but( within tolerence +/- 5%) .
    there's no opvious shorts in primary or secondary side except the HOT that's out of circuit now , the B+ switching regulator fet is intact and not shorted even the HOT was shorted.
    i need any closest readable schematic for this monitor and also a replacement equivalent for this HOT TT2054 .
    thanks for any help given
    Kind Regards
  • Poziom 12  
    Hi colleagues
    i have power supply that's didn't start while the Horizontal output transistor out of circuit and loaded with 60W light bulb and there should be a feedback sync pulse from the FBT to the power control IC , this pulse comes using a one turn wire around the ferriet core of the FBT and it'll be missing when the HOT is out of circuit .. does this prevent the power supply from starting up?
    how can i diagnosis the circuit then?
    i've nothing missing or bad in the power supply area and it still didn't start while the HOT is out of circuit but i beleive this is because of the missing pulse from the FBT , how can i let it start by paypassing this pulse?
    any idea?
    thanks for any help given
    Kind Regards

    Dodano po 3 [godziny] 29 [minuty]:

    Hi all colleagues
    yes , the power supply will not start unless it gets the pulse from FBT through the wire turn on the core ferrite of FBT , i've replced the horizontal output transistor TT2054 with a good one from scraped monitor , this was 2SC5301 , which has much better specs , now the monitor works fine but the transistor 2SC5301 gets too hot , the question now is :
    1- is it normal for that monitor to have the horizontal output transistor working hot like that?
    2- how to force the power supply to start working for diagnosis without receiving the pulse from FBT?
    i don't want to lose the new transistor as it's so hard to find one like that here in my country and i want to see what's driving the horizontal to work so hot but want to keep it out of circuit while the power supply working.
    any help or advice is highly appreciated
    Kind Regards
  • Poziom 12  
    Hi all colleagues
    i have got the chance to take those supply rails that comes out of the powr supply :

    D188 to C120 i have 83V
    D189 to C121 i have 52.3 ( this is the +B voltage .. is it right?)
    D113 to C119 i have -10.8V
    D102 to C125 i have 6.9V
    D10?? can't see the complete mark here , the cathode of this diode goes to C130 where i have 14.9V
    the horizontal driving signal sound ok
    is those voltage are correct?
    does any one has a schematic for this monitor?
    why the horizontal output transistor gets too hot?
    please help and many thanks for any help given
    Kind Regards
  • Poziom 12  
    hi
    any help or advice please?
    thanks for any help given
    Kind Regards