Sony STR-6046a motorboating

[STR-6046A]

My sony suddenly started making this motor boating sound. I thought it was in the right channel at first. It just appeared, Turned the Sony off one day and the next time on it was there. When I switched the pre-amp off it was gone. So I went and replaced all the caps on the Pre-amp board, but that didn't fix it. So I replaced all the Caps on the Output amp , too... and the Powersupply. To no avail.
Then I did a desperate attempt of reflowing all the solder joints ,starting with the output amp and then going to the Preamp. There I found a little curled up something stuck between two components. No clue what it is, but when I got it out, the noise was gone.
Got all Caps replaced now with nice Nichicon NKZ and she sounds pretty sweet, I must say.

here is the curled up something uncurled... I'm sure that wasn't supposed to be there.

that 1uF cap still needs to leave...

 

[62vauxhall]

A piece of foil trace from the PC board?

That orange cap may be a low loss Elna or something. Might be best to leave it be.

 

[STR-6046A]

That low loss Elna is actually made by Nichicon. But it's long gone, I took that photo while I was recapping.

I thought that too, that it could be a trace, but there is no green side, both are shiny.

A piece of foil trace from the PC board?

That orange cap may be a low loss Elna or something. Might be best to leave it be.

 

[Oldsansui441]

I wonder where that piece of metal came from, good find. I bet it does sound better after your cap replacement, 62vauxhall is correct, that orange Elna is a low leakage cap, you can replace these with Nichicon UKL's.

 

[STR-6046A]

I think I replaced it with a UKG , actually I'm pretty sure I did. Couldn't get it as a UKZ

 

[Oldsansui441]

Fair enough, yeah those Nichicon KZ's and FG's do have a fairly low leakage figure also, just not as low as the KL's. It is a bit of an apples vs oranges comparison when trying to compare new electrolytic leakage specs vs the old Pioneer tuning fork low leakage capacitor leakage specs as l have noticed they are tested over a different time factor.