Why is the volume on my right channel so low?!

[Turkeybaster]

Hey guys, new poster and hobbyist.

I have a Sony STR-k502p that I thought had a blown front right channel. After taking it in my shop and doing some problem solving steps I identified that it was not completely out, it was just running at about a quarter the level as all the others. I swapped sources, input channels, checked balance levels, yet it was always the front right at a much lower level than any of the other channels.

What do you guys think is the issue? I popped open the case and cant visually identify any obvious flaws.

[Uniballer]

Re: Why is the volume on my right channel so low?!

Burnt resistor, bad capacitor, bad solder joint, half-blown semiconductor... Start troubleshooting.

Have you seen this video? Good info (go find that online service manual). Sony STR-K502P A/V Control Amplifier

Traditional audio methods:

1. Inject a signal into the amplifier starting from the output stages back towards the input. Compare working and non-working channels as you go by the sound from the speakers. This allows you to spot the bad stage in the amplifier. Then you will need to test individual components to find the bad one(s).

2. Check signal levels through successive stages with an oscilloscope, comparing working and bad channels as you go. Same as above: this identifies the bad amplifier stage.

[Turkeybaster]

Re: Why is the volume on my right channel so low?!

When I said "Hobbyist", what I should have said was fan on the sidelines with dreams of playing

While I have a soldering iron, and passable skill with it, I have a cheap analog multimeter (which I will be replacing with a digital auto) and definitely no oscilloscope, not the skill to use one. My electronics experience comes from building and working on RC cars, so I'm a baby in your world.

I would be able to replace a part if it was identified, but I dont have a background in electronics engineering, nor can I properly read a board diagram.

I do have the repair manual though, and I am pretty good at learning from watching good Youtube vids as I am a visual learner.

I did learn a decent work around for my problem, however, if I cannot fix it. As the receiver has a separate multichannel input, I am simply choosing two of the working channels, and wiring the speakers in accordingly, to create my own stereo front right/left as needed since it is just being used as a garage workshop stereo.

[Agent24]

Re: Why is the volume on my right channel so low?!

You can also use another amplifier to trace the signal. Trace through alternating between both channels, find where the audio level drops in the faulty channel.

[CapLeaker]

Re: Why is the volume on my right channel so low?!

or with an a sine wave on the amp input and poke around with the oscilloscope.

[Uniballer]

Re: Why is the volume on my right channel so low?!

Tracing an amplifier isn't that hard. I remember finding a bad transistor in my brother's stereo this way when I was 14-15 years old, and riding my bike to the nearest Radio Shack to get a replacement and putting it in. No schematic, but not too difficult.

Try this video: Audio Troubleshooting

[Agent24]

Re: Why is the volume on my right channel so low?!

or with an a sine wave on the amp input and poke around with the oscilloscope.

Yes, that is a better way, but he already said he doesn't have an oscilloscope.

[budm]

Re: Why is the volume on my right channel so low?!

Use the computer sound card to generate 440 Hz tone to feed the amp inputs, then use True R.M.S DMM in AC mode to look at the signal level in each stages. If the meter just has simple one diode rectifier for Average AC when measure the circuit that has DC, the DC voltage will shows up in the reading, so you may have to use DC Blocking cap.
http://www.electronics-lab.com/downloads/pc/005/