Read Sharp 76FW-54H Service Manual online
DA100 (50Hz) Chassis – Article for Television Magazine
Page 64 of 80
Sharp Electronics (UK) Limited - March 2003
Revision 2
Servicing Tips
When servicing this chassis, it is advisable to remove it from the plastic support frame, by taking out
the eight or ten fixing screws. This only takes about a minute and can save many more when searching
for a component located underneath one of the bracing bars! It is not acceptable to remove any of
this support frame as this may result in the chassis cracking.
Note that the 56cm version of the chassis does not have a support frame because the base of the
cabinet and rear cover supports it. On the 56FW53H the front of the chassis locates into a slot at
the front of the cabinet. If this not correctly aligned then the PWB will crack when the rear is cover
is put on.
When pushing the chassis back into the cabinet on the 56FW53H only, take care not to damage IC705
on the bottom of the PWB. This device can catch one of the strengthening ribs on the bottom of the
cabinet if the chassis sags when being pushed back into place.
For general fault finding, the flow chart below is invaluable for tracking down the most probable fault
area. As with all fault finding flow charts it is not infallible.
It is possible to work on the chassis away from the cabinet and CRT. When power is connected to the
unit, it will start up and respond to the remote control just as if it is connected to the CRT and other
peripheral components. However, it is important to ensure that the chassis is not run in this condition
for too long due to incorrect loading of the horizontal and vertical output stages. This results in
excessive heat being generated in the driving semiconductors, which can lead to their premature
failure.
In the case of some power supply failure this is one of the most convenient ways of fault finding, and
to ensure that the chassis can be worked on for a reasonable time, disconnect the horizontal feed
resistor, R623.
If the speakers are disconnected, the protection circuit may operate intermittently. This will cause
the set to shut down. It is therefore important to leave the speakers connected. This is not a
problem as the leads are fairly long and allow the chassis to be moved without impediment.
the eight or ten fixing screws. This only takes about a minute and can save many more when searching
for a component located underneath one of the bracing bars! It is not acceptable to remove any of
this support frame as this may result in the chassis cracking.
Note that the 56cm version of the chassis does not have a support frame because the base of the
cabinet and rear cover supports it. On the 56FW53H the front of the chassis locates into a slot at
the front of the cabinet. If this not correctly aligned then the PWB will crack when the rear is cover
is put on.
When pushing the chassis back into the cabinet on the 56FW53H only, take care not to damage IC705
on the bottom of the PWB. This device can catch one of the strengthening ribs on the bottom of the
cabinet if the chassis sags when being pushed back into place.
For general fault finding, the flow chart below is invaluable for tracking down the most probable fault
area. As with all fault finding flow charts it is not infallible.
It is possible to work on the chassis away from the cabinet and CRT. When power is connected to the
unit, it will start up and respond to the remote control just as if it is connected to the CRT and other
peripheral components. However, it is important to ensure that the chassis is not run in this condition
for too long due to incorrect loading of the horizontal and vertical output stages. This results in
excessive heat being generated in the driving semiconductors, which can lead to their premature
failure.
In the case of some power supply failure this is one of the most convenient ways of fault finding, and
to ensure that the chassis can be worked on for a reasonable time, disconnect the horizontal feed
resistor, R623.
If the speakers are disconnected, the protection circuit may operate intermittently. This will cause
the set to shut down. It is therefore important to leave the speakers connected. This is not a
problem as the leads are fairly long and allow the chassis to be moved without impediment.
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