Product specifications

DA100 (50Hz) and DA50W Chassis – Repair Notes
Page 35 of 80
Sharp Electronics (UK) Limited - May 2003
Revision 3
Faults in the East/West Circuit
When fault finding in the east/west circuit, it is important to ascertain in which part of the circuit the fault lies.
Check the control output of IC801 – pin 32. There should be a parabola waveform on this pin at a base frequency
of 50Hz. It will change wave shape depending upon the amount of correction applied, so it is important to enter
the service mode and ensure that none of the adjustments are at minimum or maximum.
If this waveform is present, and changes as adjustments are made, then the fault will lie in the drive or output
circuitry. Faults in this area include:
1. R519 going high or open circuit – it is a 100kΩ connected to the 150V supply.
2. Q506 going short, open or overheating – change L603, L604, D502, D503, D504, D516 and C528.
3. D603 and D604 going open or short-circuit.
4. Dry joint on C601 and/or C610.
If the waveform is not present, or is severely distorted, or the adjustment range is poor, then the fault could be
caused by the memory IC – IC1003 or the VDP - IC801. It is recommended that if this is the case, then the
NVM is blanked (see the NVM blanking section of this article) first. If this does not cure the problem, then it is
probable that IC801 is at fault.
Sometimes it will not be possible to set the geometry correctly in all modes after blanking he NVM. In this case
it will be necessary to ensure that the EPROM (IC1002) is correct as per the information given at the start of
this article. When the correct EPROM is fitted, the NVM will have to be blanked to enable the correct
information to be downloaded into it.
Replacement EPROM’s have been produced so that minimal geometry adjustments are required. If the picture
geometry is very poor after following the above procedure, the fault will be elsewhere in the east/west circuitry.
Reference Function Part Number Comment
R519 Ramp charging resistor VRD-RA2HD104J Goes high or open – on component side of PWB
Q506 Eat/west output transistor RH-TX0151BMZZ Open or leaky – SMD
L603 Feed coil RCLIP0286BMZZ Low resistance – normally 8Ω
L604 Line earth return coil RCLIP0284BMZZ Low resistance
D502/3/4 Clamping diodes RH-DX0551BMZZ Intermittently faulty
D516 Clamping diode RH-EX0837BMZZ Intermittently faulty
C528 Reservoir capacitor VCEAGA1JW106M Leaky
D603 East/west modulator diode RH-DX0299BMZZ Open or short circuit
D604 East/west modulator diode RH-DX0302BMZZ Open or short circuit
Notes
D516 is not shown on the GF circuit diagram, although it is fitted to the chassis.
R519 is sometimes a 150kΩ resistor, check the value before replacing, as fitting the incorrect value will result in
poor east/west geometry performance.