Sansui 551 left channel distortion/issues

[Zreeber]

Hi, i recently purchased a sansui 551 to use as a phono stage for my turntable. The receiver sounds amazing but i am having a few issues. When i play a record everything sounds fine, both channels working perfectly, no distortion or noise, then every once and a while the left channel will get terrible distortion, i would compare it to the sound of a blown speaker. Its always the left channel. Ive swapped to speakers to make sure thats not the issue. The weird thing is if i unplug the left RCA input from the back of the receiver and plug it back in the distortion goes away and everything goes back to normal. I originally thought it might be a problem with my RCA cables from my turntable so i bought an 3.5 mm aux to RCA cable to try in my AUX port. after a few minutes of playing through the AUX port i had the same issue. Sometimes the issue happens quickly, sometimes i can listen to music for a while before it appears again
The other issue im having is with the AM/FM. the right channel works perfectly fine, but the left channel is always only noise, like the sound of a bad signal. sometimes you can faintly hear the music from behind the distortion if the radio signal is strong enough. Could these two issues im having be related? Any tips would be greatly appreciated on where i should start with troubleshooting this problem, this is a great sounding little receiver that works well in my space and id love to be able to use it all the time without the hassle of having to unplug and replug in the rca cables every time i get noise.
thanks

 

[tutor_turtle]

First, clean all switches and potentiometers with DeOxit. Fader Lube™ for the pots, D5™ for the switches.
Next, clean the RCAs with a low-abrasion cleaner. I found Luster Lace used with an 11/16 nut driver cleans them nicely.
If that doesn't do the trick, you do indeed have a hardware issue.
You'll find the circuit is quite simple with a dozen critical parts, at most. (caps and transistors) on a board not much more than three inches square.
If you find this to be the case, it will almost certainly to come down to a transistor. Change them all.
If the tuner crunches when you turn the knob, the (variable capacitor) shaft bearings need a drop of light oil (typewriter oil: 0W) D5 might do the trick.
Don't spray directly on the tuning cap, it will mess with the alinement. Coat a cotton tip swab and go easy, less is more.

 

[Jefft91]

I've had this symptom with a cold solder joint on a transistor and also with a bad mechanical connection. I'd be checking for cold solder joints in addition to @tutor_turtle suggestions for switces and hardware, but do the easiest things first of course.

 

[tutor_turtle]

I just had an interesting problem on a model 771 receiver that came through the shop this week.
The dashboard lights were flickering, causing noise throughout the system.
The lamp clips (all of them) had solder fractures from years of heat cycling. Reflowing the joints fixed the issue.
This is also a common problem for the regulators in the power supply section. They can get crazy hot, as the heat sinks are typically under-sized.

 

[parman]

I have a 771 with left channel issues and it started with flickering lights. I would really like to get it sorted

 

[davidhun]

I recently recapped and replaced some transistors in my 551 with a similar problem on the same channel.

I believe 2SC1312 is on the shoot-on-sight list. The culprit for me, however, was TR11. Dust accumulation bridging the legs of the transistor was definitely a contributing factor.

Here's a list of what I [attempted] to replace in that circuit. Note TR09,10 :

Number​	Original​	​	Found​	​	Replacement​
TR01,02​	2SC1312 (G)​	​	2SC1312G​	​	KSC945CYTA​
TR03,04​	2SC711 (E,F)​	​	2SC711E​	​	KSC1845FTA​
TR05,06​	2SC1000​	​	2SC1000GR​	​	KSC1815YTA​
TR07,08​	2SA697 (C, D)​	​	2SA697​	​	KSA916YTA​
TR09,10​	2SC1166 (O, Y)​	​	2SC1211D​	​	KSC2383YTA (NOT SUITABLE)​
TR11,12​	2SA661 (O, Y)​	​	2SA697​	​	KSA916YTA​

The KSC2383YTA was recommended as a replacement for 2SC1211D here but didn't work for me. Full disclosure, I was in "hurry up mode" and maybe needed to reverse it; I don't remember. I just put the original back because it wasn't a problem transistor.