YAMAHA A840 7.1 RECEIVER TURNS OFF ITSELF

[designerturk]

hi everyone i m new in this forum.
i bought a yamaha a840 7.1 receiver
it was stuck on blinking red light and i reset the unit.now after 3 seconds it shuts itself .what could be the issue? please help if you have any experience on this specific issue .

 

[avionic]

Welcome to AK... Good Luck with your project.

 

[mbz]

I couldn't find the service manual, maybe others will have better luck.
The amp is in protect mode, the first step is to enter "Diagnostic Mode"
and read the protection reason, a 3 key sequence is required however
without the service manual... The Key sequence for the RX-A2020 is,



Unlikely this sequence will apply to your amp.

Types of protect are,
I PROTECT (short)
DC PROTECT
PS PROTECT

3 second shutdown suggests abnormal power amp DC voltage, eg, shorted output transistor.
Without a service manual this would require a tech to fix, ie, test output and driver transistors...

 

[designerturk]

hi thanks or reply now it doesnt power up at all . before had similar issue with another amplifier and i changed the smal capacitor it worked but this one is different

 

[mbz]

now it doesnt power up at all

Suggests the amp has moved to over current/I PROTECT. Power up is aborted to prevent serious damage

had similar issue with another amplifier and i changed the smal capacitor it worked

Yeah, years ago this got a lot of "press", there's a 22nF cap on the subtrans board that had a high failure rate. You could
try and track it down, typically orange or brownish colour, located near the small transformer. Going to be difficult without
a service manual, suggest take a look at the power supply voltage regulators and caps, normally a top board with 6 or
so heatsink voltage regulators, check supply voltage to each, maybe post a hi-res pic of the board.