My SONY DAV-HDX275 DVD Home Theatre System isn't turning on

[FallenHero02]

I have a SONY DAV-HDX275 DVD Home Theatre System that keeps breaking when I try to fix it.
We've had this sound system for many years without any issues but only recently did it "die" for some reason. Upon later inspection, I found that the fuse blew.
The fuse that it was using was a 6.3A 250V fuse. I was able to acquire one and then replace it. It worked after that when I turned it on straight after putting the fuse in. After this, I didn't use it for a few weeks. When I did get to use it, it worked. But then about a week later I went to use it again and it didn't turn on again.
I believe that it is once again the fuse but I do not understand why the fuse blew again.

Can someone please help me find out what the problem is so I can fix it?
 

[bob91343]

Obviously there is an overcurrent somewhere.  First, replace the fuse and then measure the current through it.  If it's safe, then you have an intermittent problem.  If it's marginally close to rating, then you need to find out why.

The problem is likely in one of two places.  The power supply or one of the output amplifiers.  Once you decide which, it should tell you where to look.

[SpecialK]

Well let's see what we know.  It's a tiny revice for being a 5-disc DVD player plus having six amplifier channels.  So it's a switch-mode power supply because clearly it doesn't have enough iron (large transformer) for a properly sized linear power supply.

Now according to the service manual available on-line, there are several devices I am suspicious of in the power supply:

• C901 Mylar capacitor across AC line.  Assume for noise suppression or PFC.
• TH901 Thermistor to limit in-rush current.  Seems like this is an issue.
• C903 main supply filter capacitor.  These are often killed by the severe ripple currents in SMPS.
• VDR901 varistor for AC line regulation