56FW-53H. DA100 Repair Notes - Sharp TV Service Manual (repair manual). Page 16

DA100 (50Hz) and DA50W Chassis – Repair Notes 

 

removed, the current flowing from source to drain will decrease, the volt drop across R716 will decrease and 
Q702 will turn off, allowing the gate to rise again.  If the over current condition continues, the power supply will 
trip. 
Q702 is also turned on by pin 15 of IC702 during standby to turn the power supply off.  On Dolby Pro-Logic 
models this signal controls the operation of the Dolby Pro-Logic power supply. 

 
Note that the above waveform has been taken on the primary side of the power supply.  It is therefore essential 
that an isolation transformer be used in conjunction with the set.  This will ensure safe connection to the primary 
side reference. 
This waveform will also change in pulse width depending upon the load demanded from the power supply.  The 
greater the load the longer the on time.  The FET will switch on at about 4.5V, this is indicated as a short 
levelling off period on the upward ramp. 
 

Sharp Electronics (UK) Limited - May 2003