Product specifications

DA100 (50Hz) and DA50W Chassis – Repair Notes
Page 45 of 80
Faults in the Audio Circuit
Faults in the audio stage are normally caused by high HT (see power supply section for more details on this fault
scenario). When the HT become excessive, it is possible for one or all of the audio output IC’s to fail. Usually,
the feed coils L350 and L351 (for IC301) and L315 and L316 (for IC302) will go open circuit as the IC draws
excessive current. The part number for these coils is VP-CD3R3K0000. Remember to also check IC1302 on the
centre speaker PWB as this also fails. The feed coils are L1302 and L1303, which have the same part number as
the main channel feed coils.
If a whistling sound is heard from the centre speaker, it could be that it is beating with either of the main audio
channel amplifiers. In this case R1312 can be changed for an 8k2Ω resistor (Sharp part number VRS-
TV1JD822J). This will change the frequency of operation of the class D amplifier and stop the beat.
If the speakers are left disconnected (left, right and centre), it is possible for the protection circuit to operate.
This can be particularly frustrating when repairing a set. As the leads connecting the speakers to the PWB are
fairly long, they can be kept in situ, even when the chassis is tilted to provide ease of service.
IC1300 on the centre speaker PWB can run hot and result in a dead set (short circuit on +16 or - 16v rails). To
reduce the operating temperature of IC1300, add jumper wires JL2 and JL3 as shown in figure 41.
Check for and if necessary re-solder dry joints on C1306. Also check the condition of IC1300 and replace if
necessary. Note that if the track is cut below IC1300 and jumper link JL1 is fitted (as in figure 45) it is not
necessary to carry out the modification as detailed in figure 46. The parts required for this improvement are
listed in the table below.
Reference Description Part Number
JF2 Jumper VRS-TV1JD000J
JF3 Jumper VRS-TV1JD000J
IC1300 Op-amp IC VHIBA4558F/-1
In the case of a dead set, caused by short circuit IC1300, it is possible to run the set by completely
disconnecting the centre speaker PWB.
Figure 45: Centre Speaker Modification 1
Sharp Electronics (UK) Limited - May 2003
Revision 3