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DA100 (50Hz) and DA50W Chassis – Repair Notes 

 

 

 

Sharp Electronics (UK) Limited - May 2003 

 

DA100 (50Hz) and DA50W Chassis – Repair Notes 

 

It can be seen in the waveform that there are 'noise spikes' throughout the display.  This is due to the 
oscilloscope being used to record this picture.  An analogue oscilloscope will display a smoother curve. 

Sharp Electronics (UK) Limited - May 2003 

 

DA100 (50Hz) and DA50W Chassis – Repair Notes 

 

Sharp Electronics (UK) Limited - May 2003 

 

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. 
 

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. 
 

DA100 (50Hz) and DA50W Chassis – Repair Notes 

 

There are two types of CRT PWB fitted to this chassis.  One is for use with the 66cm and 76cm versions of this 
chassis and the other is for the 56FW53H only.  The major difference is that the 56cm model does not have a 
scan velocity modulator or picture rotation circuits on this PWB.  This means that it is physically smaller than the 
other models. 
Note that the CDA IC, IC1801, can be one of three types – see note in IC Identification section. 

 
 

It is possible for the grey scale to wonder, picture brightness to ramp up or down.  If the G2 is set correctly, 
IC1801 is suspect.  Check by substitution. 
If the reference voltage on pin 2 of IC1801 is about 10V, picture smearing will occur.  This is normally on the red 
channel.  If the voltage is below 9V the picture will blank.  In both cases, Q912 or its associated components can 
be responsible.  This transistor can get hot during operation (especially on the GF models due to more current 
being drawn through the device).  If you suspect that the transistor may fail due to its temperature being too 
high it is permissible to fit a 68Ω, 0.5W resistor between the collector and emitter of Q912.  It is easier to fit 
this resistor to the print side of the PWB.  

Sharp Electronics (UK) Limited - May 2003