Onkyo amplifier A-RV401 - output signal to speakers cuts intermittently

[gerolo]

Hi everyone,

I'm kind of a newbie on troubleshooting electronics issues, so any pointers on the following will be greatly appreciated: I have an integrated Onkyo amplifier, model A-RV401 (bought in 1994). For the last few years, I've noticed that the audio output to the speakers is cut intermittently (mostly on the right channel), when listening to sources connected to any of the A/V inputs at low input levels.

According to what I've observed, the problem is not related to the volume knob or bad speaker connection. A momentary workaround is to quickly turn the volume up and then back to the previous position, but after a few secs/minutes sound starts to get scratchy again. Today I plugged my MP3 player to the front A/V input, and started getting scratchy sound when turning the volume of the MP3 player all the way up, and the amp volume to a 1/4 of its total approx. However, I found out that even if I turn the amp volume up a little and then turn the MP3 player volume down, the problem still shows up - so it's kind of related to the level of the signal that is fed to the speakers, rather than to the position of the volume knob.

I've read several posts concerning faulty capacitors in old amps, and how they affect performance. I've got an schematic of my amp's circuit board, but I'd appreciate some pointers on where to start checking for any faulty components.

Thanks in advance for your help!!!

[tangmonster]

I would suggest posting the circuit diagram

Also , mostly capacitor problems only happens in MUCH older amplifiers than yours.

What i have found in a few 90's and up amps is that they use 78xx and 79xx chips in a few places and that i have had them become intermitted due to very poorly designed too small heatinks.

One time I thought it was a 7805 that had a problem and then it turned out to be a very small bridge rectifier before it.

So like always , test all the power supply voltages on the 78xx and 79xx pins and any other power sources. Since it's only one channel I might be on the wrong path..

And it might be an opamp...

[sakis]

it could be a number of things ...one that is easy to trace down is the output protection relay if exist .... keep the cover open watch out for dngerous voltage and use a plastic pen to tap over the relay while playing music

by the same logicand always with aplastic part and always carefull you may tip and tap here and there over the pcb to locate a loose connection or bad soldering

i also agree to capacitors .... they seem quiet yound to be replaced ... but look also for the obvious ....fluids arround them , salted corosion of any form , signs of thermal stress here and there

post pictures ...post a schematic if its available

regards sakis

[schepbo]

i have the exact same problem, same amp

[stoc005]

More than likely it is the speaker protection relay that is dirty. If it has them, tap each one and see if the sound returns or is intermittent. Clean them with contact cleaner and fine emery paper, 600 or so grit. If sealed, be prepared to replace them.