Product specifications

DA100 (50Hz) Chassis – Article for Television Magazine
Dolby Pro-Logic Circuit Operation
Dolby Pro-Logic functions are provided by a separate PWB on the models ending with the number 4, i.e.
66GF64H. This panel contains all the power supply, processing IC’s and output devices required for
the Dolby Pro-Logic function. The PWB is virtually identical between models, except that the GF
models route the sub-woofer output onto the main PWB as it exits the DPL processor (IC1301). It
also uses a different output on IC1301 for the sub-woofer. This means that the FW and GF PWB’s are
not interchangeable.
The power supply is identical in operation to the main chassis, but only generates four supplies. +/-17V
supply for the output amplifiers, +8V for the Dolby Pro-Logic processor and a +5V supply used for the
muting circuits. This power supply is turned off during standby by IC702 on the main chassis in the
identical way to the main power supply
A stereo signal is fed into the Dolby Pro-Logic PWB from the MSP. This is either derived from the
off air NICAM source or an external AV source. This signal is converted into a Dolby Pro-Logic signal
by IC1301 from which it is outputted to the various channel amplifiers as listed in the table below.
Speaker Output IC Number Impedance IC1301 pin – FW IC1301 pin – GF
Left IC1302 8Ω 24 – DACC1_L 24 – DACC1_L
Right IC1303 8Ω 23 – DACC1_R 23 – DACC1_R
Surround IC1304 16Ω each speaker 27 – SC1_OUT_R 31 – SC1_OUT_L
Sub-Woofer IC1305 4Ω base reflex 21 – DACC2_R MSP (IC305) pin 31
Note that the output from the surround amplifier is connected to two 16Ω speakers. Both speakers
are connected in parallel, but in anti-phase to each other. If the front speakers are connected to the
rear speaker output, IC1304 will eventually fail. Invariably the customer will complain that the rear
speakers did not have enough volume before the IC failed.
The power supply used on this PWB is similar in operation to the main chassis, but the heatsink
containing the chopper transistor gets very hot. Sometimes it is too hot to touch - this is normal.
Figure 47: Pro-Logic PWB
Page 47 of 80
Sharp Electronics (UK) Limited - March 2003
Revision 2