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Monitor IBM 6547-2BN fault

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Full Member level 6
Oct 30, 2004
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hi all colleagues
i have this IBM 6547-2BN built on samsung chassis CKB5237L which is dead apart from the power green led blinking once a second (nearly) and the relay clicking on power up . All the supply reails are comming correct and i can measure 50V on Collectors of both Q503 and Q406 , couldn't find any short horizontal area , all the supply rails of power supply are comming correct , 50V,80V,13V,7V,-12V .. all are ok except the missing 12V which comming from pin 2 of IC603 which measures about 1.1V and was disabled by Q604 (suspended by MCU) , if i disconnect Q604 base the 12V commes up again wich reveals non-faulty IC 603 , checking both Hsync and Vsync inputs @ pins 24 and 15 of IC 202(MCU) , proved they are present , also they come out of pins 21 and 20 of MCU , i have ocsillator activities around the crystal pins which reavel a working oscillator and crystal .
the supply voltage to MCU is 5.5 to 5.6 V @ pin 10 and there's 5.5V also present @ pin 25 of MCU , the supply voltage is regulated by IC600 which drops down the 13V supply rail to 5V for micon .. i couldn't find anything wrong or missing ??!!
one more thing i've noticed is pin 12 of MCU , H-Protect is high (5 to 6V) ,this indicates an OCP mode , when i disabled this , the HOT Q503 got very hot and no raster appeared .. does this means a faulty FBT?
any help or hint would be greatly appreciated

Added after 5 hours 18 minutes:

hi again
here's the service manual for this monitor in case someone needs it or wanna have a look to help

It may be FBT, you can check this making a frecuency measurement in driver Trs, on base you must be the oscilator frecuency and the colector must be double of frecuency on it or in horizontal out

hello ramonglez59
that post was so old and it turned out to be the FBT .
thanks for trying help
Good luck

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