Old dolby pro logic amp not outputting to rear speakers on pro logic mode, yet it will output to rears if using 5.1 in

[ArAnd0mPers0n]

I'm using an old amp that I literally found on the side of the road (Fisher TAD-9925, and i'm not upgrading since I don't have the cash to do so) and for some time the pro logic surround functions worked. Out of nowhere they have stopped functioning, and sound only comes out of rear speakers if the 5.1 input on the rear of the unit is used instead of the stereo input with the pro logic functions. What can I do to make them work again? By the way, I am pretty experienced with soldering and repairing electronics (Although for this specific amp I don't have much experience, since I only replaced the STK411-230E in it, and it has a very complicated construction.

 

[americanaudiophile]

Since the 5.1 input works I would guess that the Dolby chip is bad.

 

[ArAnd0mPers0n]

Since the 5.1 input works I would guess that the Dolby chip is bad.

Which one? There's two in the amp: LA2787 and a LV1017.

Edit: After a little looking I think the LV1017 may be the chip to replace. You think this is the case too?

 

[americanaudiophile]

Can't say but searching briefly I can't find the LV1017 for sale online. The LA2787 is out there.
If you enjoy fixing this stuff then have fun but if you can find a used Dolby Digital receiver it will sound way better than the Fisher which is actually Sankyo and comes from a package system.

 

[ArAnd0mPers0n]

Can't say but searching briefly I can't find the LV1017 for sale online. The LA2787 is out there.
If you enjoy fixing this stuff then have fun but if you can find a used Dolby Digital receiver it will sound way better than the Fisher which is actually Sankyo and comes from a package system.

I'll just say one thing though, I actually prefer the sound of pro logic receivers, but thanks for the advice.