QuestionHi, like the title i have a Sony receiver STR-230a made in Chile. The thing is that it works fine until certain time, like 15 or 20 minutes, and then starts a really loud and erratically noise, even with low volume, so loud that you have to shut it down.
Then when you turn it on it's fine but this time in a couple of seconds began the same loud noise. At first i thought it was dirty in the contacts of the volume, because when i moved them it starts that noise but low and then in a while loud. So i cleaned them really well but nothing. I found (a lot time ago) some fuses broken and a repair with cable jumping the fuses, of course i bought the fuses to replace them but maybe something could broke in the time it was working with that "jumpers".
I think it's something that gets overheated but i don't have the schematics neither the knowledge to solve this.
Also i hope you can understand or guess anything I've said, i have a really bad English.
Thanks for your help. See you.
AnswerEnglish is fine. Fully understand the problem.
IF: Loud nosies come even with volume down low or zero that means the noises are coming into the circuit after the volume control. So, we must consider the power output stages or the power supply line that is feeding the power section. You are smart to consider the volume control as it can cause such symptoms but usually it will settle down after rotating it a few times to clean out the surface dirt inside the volume wiper element.
So, I am thinking it is related to a bad electrolytic capacitor inside the power supply section. It can take a very long time to fully charge up the electrolytic fluid inside that is causing the problem. The electrolyte can be chemically deteriorated or leaking and causing short circuit inside the housing of the capacitor.
The capacitor will be a large one, like 400MFD or 500MFD with 50v or 60v rating. I am guessing but that is usually what one would expect.
Let me know if you need further ideas.
