CTV2003 06 01
Month of Issue: 18
TELEVISION TECHNICAL BULLETIN
Page 1 of 2
Sharp Electronics (UK) Limited
Reference AVW 06062003 - 1
White – Carry out as required
Yellow – Carry out as required and whenever the unit comes in for service
Red – Carry out on all units
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 100k
Ω 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 or
re-flashed 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 (see CTV2001 05 04). 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.