Marantz SR4320 very distorted channel

[Wehan]

I have a Marantz SR4320 receiver and it has a very distorted and garbled right channel. Where might I start looking for issues and/or can someone walk me through troubleshooting this thing? Somehow missed this on the first quick pass lol but I have found A problem and hopefully THE problem (See pics).

[R_J]

Re: Marantz SR4320 very distorted channel

It almost looks like something was spilled in that area, try replacing the burnt resistor, check the transistors in that area, like Q318 etc.

[Wehan]

Re: Marantz SR4320 very distorted channel

It almost looks like something was spilled in that area, try replacing the burnt resistor, check the transistors in that area, like Q318 etc.

Can these transistors be checked in the circuit or do I have to pull them and test?

[R_J]

Re: Marantz SR4320 very distorted channel

You can test them in circuit, if they check shorted or maybe not right, then remove & test them out of circuit, you can also compare the reading with the same transistor in the working channel.
Have you tried just replacing the resistor to see if it works, Just keep an eye on it when you turn on the amp, if the resistor starts to smoke, check for shorted transistors.

[Wehan]

Re: Marantz SR4320 very distorted channel

You can test them in circuit, if they check shorted or maybe not right, then remove & test them out of circuit, you can also compare the reading with the same transistor in the working channel.
Have you tried just replacing the resistor to see if it works, Just keep an eye on it when you turn on the amp, if the resistor starts to smoke, check for shorted transistors.

Checked the transistor against the good channel and it seems like it's bad, I get pretty steady reading on the good chanel but on the bad channel the resistance starts out nearly twice as high and keeps going up quickly.

[AsRock]

Re: Marantz SR4320 very distorted channel

That dark crap what i think it is ?, isn't that the stuff that goes conductive ?, if so might be under the cap(s) too.

[Wehan]

Re: Marantz SR4320 very distorted channel

That dark crap what i think it is ?, isn't that the stuff that goes conductive ?, if so might be under the cap(s) too.

Did not know that could be conductive, gonna have to double check but I believe the caps there have some hot-snot all around them.

As an update; replaced the resistor and pulled the transistor but it checked good out of circuit. Just need to get some mica transistor insulators and I'll have it back together.

[redwire]

Re: Marantz SR4320 very distorted channel

Looks like R352 burned up. 100R 1/4W. That is the for the -ve rail for the right channel power amp driver and voltage amp stages.

I would expect other resistors like R348/R346 100R to also burn up.
Shorted C314 is the only thing I can see that would cook just this one part.

[Wehan]

Re: Marantz SR4320 very distorted channel

Looks like R352 burned up. 100R 1/4W. That is the for the -ve rail for the right channel power amp driver and voltage amp stages.

I would expect other resistors like R348/R346 100R to also burn up.
Shorted C314 is the only thing I can see that would cook just this one part.

R352 has been replaced, Q316 has checked out good, R348 and R346 appear good, pulled C314 and C312 and both are rated at 220uF but measured out to be 203uF each. Is this an issue or are they within tolerances?

[R_J]

Re: Marantz SR4320 very distorted channel

They are not that bad, and not the cause of the problem. most caps like that are 20% tollerance. and they are not new so they may check a bit low, change them later if you like.
Have you tried turning on the amp after replacing the resistor?

[Wehan]

Re: Marantz SR4320 very distorted channel

They are not that bad, and not the cause of the problem. most caps like that are 20% tollerance. and they are not new so they may check a bit low, change them later if you like.
Have you tried turning on the amp after replacing the resistor?

Yeah, I found the M rating on them = +- 20% and they are -7% so they are perfectly fine. Haven't turned the amp on yet because the mica insulators under Q323-326 split apart, replacements should be here any minute.

[Wehan]

Re: Marantz SR4320 very distorted channel

Got the board along with new Mica strips and ceramic thermal compound installed.

Good news: the new resistor didn't smoke and seems to be doing just fine.

Bad news: I have next to no output from headphones or speakers, I get a very quiet output when the volume is all the way up and that's it. confirmed the issue is present on channel a and b left and right and on multiple inputs and tuner. seems I might have goofed something else up?

HAHAHAHA I fixed it, APPARENTLY These jumpers HAVE to be installed to get any sound!!!

Works awesome now!

[R_J]

Re: Marantz SR4320 very distorted channel

Glad its working, simpler than you thought. I have seen a lot of amps where someone forgot the loop throughs from pre out to main in.

[AsRock]

Re: Marantz SR4320 very distorted channel

Got the board along with new Mica strips and ceramic thermal compound installed.

Good news: the new resistor didn't smoke and seems to be doing just fine.

Bad news: I have next to no output from headphones or speakers, I get a very quiet output when the volume is all the way up and that's it. confirmed the issue is present on channel a and b left and right and on multiple inputs and tuner. seems I might have goofed something else up?

HAHAHAHA I fixed it, APPARENTLY These jumpers HAVE to be installed to get any sound!!!

Works awesome now!

Been there done that with the jumpers lol, Good to hear you fixed it.