up voltage(around 15 to 17.5V), U901 UC3842 will start to work and output 5V at pin 8. If
voltage on U601 pin 7 is too low, check and fix following circuits
：
start up circuit R914,
and C914.
3.1.4 If no output pulses at U901 pin 6, check and replace U901.
3.1.5 If driving pulses at U901 pin6 and drain of Q901 are correct but voltage at U901 pin 7 low
than threshold voltage --causing U901 to stop and restart periodically, check and repair
following circuits. Power transformer T901 bad; D903 short-circuit/opened.
3.2 No Display, power output normal.
3.2.1 Check and fix FBT B+
：
If no B+
（
27.5V
）
on pin2 of FBT replace D906, C916.
3.2.2 Check driving output voltage
：
0 or very low check and replace Q402, Q401.
3.2.3 Power off monitor. Check yoke connection. Use multimeter to check D501, D502, D401, Fix
if any is bad.
3.2.4 Power on, check voltage at pin10 of U401 if no voltage, check and fix Vertical circuit B+,
D904.
3.3 No Display (No Raster).
3.3.1 Check yoke connection.
3.3.2 Check CRT board and verify CRT heater is on.
3.3.3 Check G2 voltage if fail, check and fix FBT or D502.
3.3.4 Check K (cathode) voltage at negative of D501 about 150V, If no voltage output Check and
replace D501 and C501.
3.4 Vertical Deflection Failure
3.4.1 Vertical display can't be held--check and fix
：
U401.
3.4.2 Vertical raster abnormal (one horizontal line, size too small or fold back on top / bottom) --
check and fix
：
14V supply at U402 pin2, if has voltage check and fix U301.
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