Audio Systems: STR-DE675 volume button not working, sony str de675, tact switches

Question
QUESTION: Hi,
I have a Sony STR-DE675 and the volume button is not responding anymore (turn it - nothing happens). I almost never use it so it's not a big issue but I would still like to know if there's any way to fix this.
Thank you

ANSWER: When you turn on the unit, do you hear a few clicks?  There should be one followed shortly by another.  If not, I suspect that the outputs have a problem and the unit is in protect mode.  Update this with what you find and I'll look up this model for the most likely parts.
Dan

---------- FOLLOW-UP ----------

QUESTION: Thank you for the quick reply.
Yes the clicks are there and the unit is working fine using the remote. I almost never use the buttons on the unit itself, I always use the remote. Last night after I discovered this problem I started pressing all the buttons to see if there are other problems and I found another one: if I press the muting button in rapid succession a few times it not only mutes the sound but also changes the sound field. That's just strange...If it press it at a "normal" pace it does what it's supposed to do  but if i press it rapidly it does this...
I spoke with a sony service and they said it takes a week to service it. It is the heart of my sound system, everything is connected to it and one week without sound seems forever. This is why I am asking you for a in-house solution (the warranty period is over anyway)

Answer
Sony's service won't be cheap either.  Their service plan is usually a fixed repair cost regardless of the problem.  For your problem, I would suspect a stuck button or a noisy one.  As long as the remote works, I wouldn't worry about it.  The buttons on these units are small "tact" switches.  These fail and are easily replaced.  They cost about $1.50 each.  The only other failure that I have seen that could have your symptoms is a bad cap on the data line.  Although that usually also effects the remote action as well.
Dan