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Pioneer SX 780: Problem Playing in Stereo

Hey everyone.

I have a Pioneer SX-780, that I have had for about five years now. It has always been in perfect working condition until yesterday when I stopped getting any decent level of volume out of my left speaker, when playing a record in stereo. There is a very faint amount of sound that comes through when playing at about half throttle, but nothing at a listenable level.

When played in phono, the speaker produces fine out of both speakers, but switching back over to stereo gets me nothing. Playing through the auxillary input off of my computer in stereo works fine as well, so its somehing to do with phono in stereo?

Thanks in advance for your help!!

Re: Pioneer SX 780: Problem Playing in Stereo

It's fairly easy to determine if its the receiver or turntable at fault.

Just connect each of the turntable leads in turn to the working right channel phono input of the receiver. If you can hear music at the same level through both leads then it's the receiver at fault (dry solder joint/switch/component failure etc). Double check this by trying each lead on the left channel input to confirm the input is faulty. If only one lead makes a sound then it could be a break in the turntable lead/faulty cartridge/poor connection etc.

Re: Pioneer SX 780: Problem Playing in Stereo

I assume that you mean there is a problem when playing in FM stereo mode; your first paragraph says there is no left channel when playing a record then you say phono works fine. It would appear that you have a FM stereo multiplex problem; could be the IC that performs this function or the function switch is dirty.

Re: Pioneer SX 780: Problem Playing in Stereo

Sory, I will try to make it more clear. I have no sound coming from my left channel when playing my record player, through phono on the stereo setting. When i play through phono, in mono, the left channel works fine. As well, playing through auxillary, or radio, in stereo, the left channel works fine. He only time the left channel doesnt work is playing amrecord player, in phono, on the receivers stereo setting.

Re: Pioneer SX 780: Problem Playing in Stereo

The easiest way to test the phono input is to use a stereo RCA cable; plug it into the phono input and listen for hum at a very low volume level--touch the center pins and you should hear hum on both channels. If you get hum on both channels, then you have a bad turntable cable, bad cartridge, loose wire at the cartridge or bad tone-arm wiring (unlikely).
If the problem is in the SX-780, it is probably the phono pre-amp; could be bad capacitors or even a defective transistor.

Re: Pioneer SX 780: Problem Playing in Stereo

You may have a problem with the phono input cables, or the phono preamp, or the switch itself.
I cannot determine that over the internet.
Reasonably speaking, it's got to be trouble-shot on my testing bench.
Some answers are just not available through the internet.