Howdy Everyone
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
I recently picked up a HTR-5280 for a fiver at a thrift store. I cleaned it up and powered it on, and everything seemed fine. Had it on for say, an hour or so. No issue.
Next day I go to power it on, it stays on about 5 minutes, then powers off. I power back on, again the same. Eventually the time it would stay powered on would become shorter and shorted. So now, it powers on (ie, lights up) then quickly turns off. I learned that these units have a protection mode that you can bypass for further testing, but even with it bypassed, it would quickly turn off.
So i opened it up, and started testing things. I have limited knowledge with stereos and the like, but tested the voltage regulators. I really couldn't get the unit to stay on long enough to test in circuit, so I decided to remove them and test with a power supply. Sure enough, on of the 7805's was only outputting around 1.5volts instead of 5v. So i ordered some of them up. (I actually ordered them all to just go ahead and replace them all, but only the 7805's have shown up. The other did test ok)
I then reassemble and power back on, same thing. Darn. However this time, when i power on with the protected mode bypassed, it stays powered on. So that's good.
But, if i disable protected mode and power on. then power it off, and power on normal, it stays on. It only seems like it wont power on when its been cold for a bit. and when it does, if i bypass that protected mode, power on, power off, power on.. it stays on.
Again, I'm pretty new to electronics in general, but for some reason, I'm thinking there could be a capacitor issue? And the reason why I say that is, its almost like if i force it to power on, it charges up that capacitor enough to bypass the protection mode kind of thing. I might be completely barking up the wrong tree though.
Any ideas of what should be checked next? I appreciate any info. Thanks all!
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)