Hi



I am currently attempting to repair my Creative Labs Desktop Theatre
amplifier, I am getting no output from the Subwoofer channel, if you run the
speaker test this again provides white noise in turn on each channel but no
output on the subwoofer. (Yes I have confirmed that the speaker is working
ok)



Unlike the other 5 channels the subwoofer does have a line out, if I connect
an amplifier and speaker to the subwoofer line output and run the speaker
test I do get output on all 6 channels therefore I believe the decoder card
is working correctly.



I have dismantled the unit and checked all connections they visually appear
to be ok, also the unit is on two PCB's a decoder pcb and the 6 channel
amplifier pcb, the subwoofer line out is also on the amplifier pcb therefore
the signal must be getting that far.



If I touch the input pin of the subwoofer power amp IC I get the expected
mains buzz, therefore I am fairly happy that the power amp chip is working.
Therefore it must be in the preamp stage someware.



I did try to obtain the circuit diagram from Creative but they said,
"Unfortunately I cannot give you a circuit diagram of the amplifier. We
don't supply this kind of information" which was polite but not very useful.



Before I sit down at attempt to trace the circuit out I was wondering if
anyone had already done this. Also each channel has an 8 pin IC marked 072D
and JRC, I dont recognise JRC but I am wondering if it is a dual opamp like
a TL072, from what I have traced of the circuit so far it does look
possible.



Has anyone had any experience repairing one of these, or recognise the chip.



Thanks

Dave

Just in case anyone was interested, I found a dry joint and it is now
working fine.
Dave

"Dave Widgery" wrote in message
...
Hi



I am currently attempting to repair my Creative Labs Desktop Theatre
amplifier, I am getting no output from the Subwoofer channel, if you run
the
speaker test this again provides white noise in turn on each channel but
no
output on the subwoofer. (Yes I have confirmed that the speaker is working
ok)



Unlike the other 5 channels the subwoofer does have a line out, if I
connect
an amplifier and speaker to the subwoofer line output and run the speaker
test I do get output on all 6 channels therefore I believe the decoder
card
is working correctly.



I have dismantled the unit and checked all connections they visually
appear
to be ok, also the unit is on two PCB's a decoder pcb and the 6 channel
amplifier pcb, the subwoofer line out is also on the amplifier pcb
therefore
the signal must be getting that far.



If I touch the input pin of the subwoofer power amp IC I get the expected
mains buzz, therefore I am fairly happy that the power amp chip is
working.
Therefore it must be in the preamp stage someware.



I did try to obtain the circuit diagram from Creative but they said,
"Unfortunately I cannot give you a circuit diagram of the amplifier. We
don't supply this kind of information" which was polite but not very
useful.



Before I sit down at attempt to trace the circuit out I was wondering if
anyone had already done this. Also each channel has an 8 pin IC marked
072D
and JRC, I dont recognise JRC but I am wondering if it is a dual opamp
like
a TL072, from what I have traced of the circuit so far it does look
possible.



Has anyone had any experience repairing one of these, or recognise the
chip.



Thanks

Dave