Sony STR-DE445 wont go out of PROTECT-mode

[mtoivanen]

Hi! I got Sony STR-DE445 for free because it originally had weird noises in front right channel, which would go away if you bump the connectors or the amp itself. So, I took it apart and fixed a lot of cold solder joints, and then put it back together. Well, now the amplifier only shows up PROTECT message and wont let me do anything I checked that there should not be shorted contacts anywhere. I also noticed when I turn on the amplifier, there is over 9 volts going to speaker connections(way over voltage I guess), and on the digital pwb, there is 7805A voltage regulator(IC1009) which goes extremely hot when amplifier is on and showing the protect message. I also checked all power transistors and they seem to be good aswell.
I'm pretty much newbie with fixing this kind of audio stuff, but it would be nice if I can get this to work Any ideas what could be wrong with this one?

[CapLeaker]

Re: Sony STR-DE445 wont go out of PROTECT-mode

You got DC on the output stage (brick is shot) or the bricks aren't making proper contact (more cold solder joints). As long that is there, the amp stays in protect mode. Since the amp was doing some weird noises first in one channel, I would resolder every single pin on those 2 output modules first. After you are done clean up your solder work with pure alcohol and an old toothbrush. You don't want to add potential damage.

[mtoivanen]

Re: Sony STR-DE445 wont go out of PROTECT-mode

Okay, this is getting weird I cleaned up all the solder on those 2 big chips, and applied some fresh solder to them. Also noticed 2 cracked contacts and more cold joints, which I fixed. Still in protect mode, but what I discovered now, left and center channels have 12 volts, and the right channel has -46VOther thing I noticed, on the front panel there is A.F.D and 2CH buttons which used to show orange light, now there is only flash or nothing. I guess one of those big chips or both of them could be faulty?

[Andrew F. Ali]

Re: Sony STR-DE445 wont go out of PROTECT-mode

Well Sir. If it was working before you attempted to repair the cold solder joints. I would conclude that you unknowingly made a short circuit on one of the joints. Retrack your steps. It happens to the best of us, so don't give up. You'll get there with persistence.

[mtoivanen]

Re: Sony STR-DE445 wont go out of PROTECT-mode

Yup, it could be possible too. I take my magnifying glass and check everything with care, hopefully that will help. And yes, it was working, but right channel only made popping and cracking sounds and if I had speaker plugged in to right channel, it would sometimes go to protect aswell, thats why I started repairing this

[budm]

Re: Sony STR-DE445 wont go out of PROTECT-mode

Service manual

[shortfoxyman]

Re: Sony STR-DE445 wont go out of PROTECT-mode

Yup, it could be possible too. I take my magnifying glass and check everything with care, hopefully that will help. And yes, it was working, but right channel only made popping and cracking sounds and if I had speaker plugged in to right channel, it would sometimes go to protect aswell, thats why I started repairing this

Hello i have the same problem.....the 7805 on digital module get very hot and it is permanent on Protect Flashing mode. Did you find exactly which is the problem?