Sony STR-DE915 no coax digital audio.

I repaired this Sony STR-DE915 receiver which had no output on any of the
channels even though the dc output was normal and the speaker relays were
clicking on. The culprits were two AC muting transistors, Q503 and Q512,
which are activated from the CPU.

I tested the analogue portion of the receiver and that was ok. Then I hooked
up a Marantz DV6200 DVD player to it and it worked fine with an optical
cable hooked up to it but when switching the input to a standard coax cable
as well as switching the input mode to "Digital (AC-3 RF)" there was no
sound. The digital coax jack on the back is labeled, "LD/DVD IN, AC-3 RF."
Is this not compatible with the current Dolby digital technology of the
Marantz DVD player?

Thanks for your reply.

 

I have that same amp. Its blown up twice, and is one of the reason I
dislike Sony.
Make sure you select the correct source on the front of the unit. And
while it may say AC-3 RF, the Sony will not decode a RF signal..it must be
demodulated first.
I found that out the hard way, when I first bought my amp to hook up to my
laserdisc AC-3.
HTH
While your at it, add a heat sink to the chip for the rear channels. It
runs very, very hot, and has no heat sink.

 

HTH

Your probably thinking of one or more driver IC's. (STK 350-230 or
uPC2581)The rear amps use heatsink mounted output transistors, same as all
the other channels. They do run the pants off those...

Mark Z.

 

Yes, the correct source is selected on the receiver and the input is coming
from a DVD player, not an LD player. I thought it would need no other help
for the signal to be decoded so I'm still wondering if the receiver is bad
on the coax input or something else is going on.

Thanks for your reply.