Loud crackling develops on its own, even after all controls were cleaned and working again.

[CdrData]

I've an old Sansui 221 which had been crackling with the volume control. I cleaned all the knobs that were causing crackle successfully, they all seem very smooth now. However yesterday before I did this I was using it and after about an hour noticed a developing hum. After another 30 min it started crackling on its own, getting so loud I had to turn it off. Subsequently I tried it and it would start the loud crackle after a few minutes. Today it worked before and after cleaning when I was testing the knobs, but it started happening again after only 30 mins. If I try turning it on again it now starts within 10 seconds.

Perhaps its the grounding?

I'm not sure what to try next, any help would be greatly appreciated!

 

[teaser]

Have You tried other power outlets in your home ?..........have you tried using a good power strip ?

 

[CdrData]

I've tried multiple power outlets to no avail, exactly the same result.

 

[everlost]

a hum i could blame on ground loop. a crackle i would lean towards switches, dials, transistors, and/or resistors.

the time factor makes this sound more temperature related, maybe mosture? when you cleaned the dials, did you disassemble them and used an alcohol solution? did you damage any wires by tugging or bending too much? or did you run them back and forth several times?

 

[CdrData]

a hum i could blame on ground loop. a crackle i would lean towards switches, dials, transistors, and/or resistors.

the time factor makes this sound more temperature related, maybe mosture? when you cleaned the dials, did you disassemble them and used an alcohol solution? did you damage any wires by tugging or bending too much? or did you run them back and forth several times?

I didn't disassemble, just took the cover off and used the switch cleaning lubricant Servisol to spray a little in each side of each dial - volume, balance, treble, bass, and selector (all of which were slightly malfuntioning and have been corrected). I also cleaned inside the phones jack (all following this: http/www.tomshardware.co.uk/forum/57120-6-cleaning-controls-jacks-info ). This stopped all the crackling resulting from moving the dials.

I just made this video of the problem: https/www.dropbox.com/s/fz2y10iys3pwsbh/3.mp4

Even with the volume at zero it still happens. Shortly after this it stopped crackling after turning it on, when I turn the volume up there is a definite hum. After leaving it off for 5 min I got an initial crackle for a few secs but it stopped. It comes and goes. By the way there is also a ground connector at the back, might that help or make it worse?

This has been sitting in a garage for maybe the last 5 years, so it may have been exposed to low levels of moisture. Maybe there is corrosion somewhere that I can't see. The reason I stopped using it was because it developed sound issues like L/R channel cutouts (found it was the selector which I just fixed), but I don't think it was anywhere near this bad back then.

 

[teaser]

those female rca jacks on the back are really dirty,clean those also

 

[everlost]

considering the VU meter didn't look like it was moving i would think the pre amp circuits are probably fine. i would also check and clean any wire joints/connections that are not soldered, an look for any cracked or broken solders.

the ground terminal would help any hum you might have on your inputs, you would use it to connect any other equipment (tape, phono) to your receiver.

 

[CdrData]

considering the VU meter didn't look like it was moving i would think the pre amp circuits are probably fine. i would also check and clean any wire joints/connections that are not soldered, an look for any cracked or broken solders.

the ground terminal would help any hum you might have on your inputs, you would use it to connect any other equipment (tape, phono) to your receiver.

The VU meter actually only shows the signal quality of the radio tuner. I'll have a closer look at all the connections and clean the unsoldered ones with isopropyl alcohol, thanks for the advice.

That makes sense about the ground terminal, I am using an Aux input. What can I connect it to that will ground it?

 

[everlost]

its not really a point to gound the reciever, like to a wall circuit. but a place to make all your equipment at the same potential. you would tie in all your equipment to this point to eliminate ground loop signals (60hz hum) from circulating through your inputs/outputs. especially if not all of your equipment has a 3 prong plug. if not all your equipment has a ground terminal, any metal chassis screw will do.