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1983 Pioneer SX-50 just went CRAZY! Please help?

S

Saffire

Active Member
Before I begin, here's a little backstory to this beautiful stereo of mine.

It's almost 40 years old now, and has never been re-capped, all original parts. But it's been working beautifully for the few months I've had it so far. Recently, there's been an issue where the stereo would lose power for a split second when cold. The display would rapidly flicker off, along with the speaker relay clicking off, and then everything would turn back on and function normally. This all would happen in a split second, and occur once or twice after the stereo has been first powered on. However, as I said, this issue only occurs during a cold start. The stereo functions just fine when it's warm and has been powered on for a little while. This leads me to believe that it's a bad solder joint at play here, but I'm not sure.

Today, I powered on the stereo, and it started going crazy! The relay started clicking off and on, like usual, but it was doing it rapidly, and the display suddenly went very dim. The dim display never happened before until now. It was all really erratic, and luckily I managed to record the incident, so I'll let you guys see for yourself:

As I type this, the stereo is sitting idle, tuned into an FM station and just chilling like nothing ever happened. I'm too scared to plug my speakers back into it. When the display dimmed, the digital VU meters were near max level, and I don't want to risk blowing out my speakers. Any thoughts?
 
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UPDATE: I may have found my problem...

I just cracked open the stereo, and on the circuit board, I found a single strand of copper wire that was bridging two capacitors together. Maybe this is the cause of the problem? Currently giving all connections a nice CRC Contact Cleaner bath.
 
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I had the sx 60. I sure love the green displays. I graduated to a SX V80. Good to see you figured it out and kept it going
 
What happens with a lot of Pioneer amplifiers is that stabilizing transistors of the power supply desolder themselves over time. Take a look at the soldering points of transistors and resolder them carefully if you detect something untidy. Do not produce short circuits in the process!
 
Thorsten R. said:
What happens with a lot of Pioneer amplifiers is that stabilizing transistors of the power supply desolder themselves over time. Take a look at the soldering points of transistors and resolder them carefully if you detect something untidy. Do not produce short circuits in the process!
Click to expand...

I'll keep that in mind for the future, thanks! The stereo works perfectly now after a good cleaning, I think my problem was a combination of a strand of copper wire where copper wire shouldn't be, along with a dirty fuse holder.
 
When I worked in my father´s shop I unpacked the very first Pioneer A-717 we got. I connected it to speakers and switched it on. Ka-bumm! Well, I switched it off at once and took the upper housing off. Out fell - a pin! Well, the amp were not damaged and played as if nothing had happened.

By the way one of my favourite amps!
 
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