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My pioneer SX-680 makes only faint sound

pio_sx_680

pio_sx_680

New Member
so I just got saved this Pioneer SX-680 from getting pitched at the dump. the guy who had it was the first and only owner. i brought it home and put a 4ohm RCA speaker on it and a variety of other speakers (up to 4 ohm) and none of them worked in any of the different outputs. everything seems to be functioning properly, but when I turn on the radio, i can tune it to different stations but i have to put my ear up to the speaker to hear anything, and its often staticy when i do hear out of it. would greatly appreciate any insight as to what may be causing this.IMG_1180.JPG IMG_1181.JPG
 
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Welcome Aboard!

First, it is important to use ONLY 8Ω speakers with this model. The audio output amplifier uses hybrid modules instead of discrete transistors, and they are very sensitive to speaker load.

Second, it will be helpful to determine whether the unit will operate normally with other input sources, such as the AUX and TAPE inputs.

Third, you will need to determine whether the speaker fuses are intact.

You may find more help in the Pioneer forum, and searching for threads related to the SX-680 may reveal a lot of useful information.
 
The one I had many years ago acted that way.
It was a bad power regulator transistor.

A good vintage tech should be able to fix it fairly easily.
 
I have a Realistic STA-960 that did the same thing. I had to clean all the switches, especially the tape selector to get full sound out of the speakers.
 
One more thing- did you connect and external antenna when you tried listening to the radio? The built in antenna only picks up AM.
 
UPDATE: so I took the stereo apart, hooked up 8ohm speakers and cleaned the board up, and tried something nuts: I switched the two STK0039 amplifiers and now instead of faint sound the speaker is a little louder, but it is fuzzy. right channel speakers still dont work and the needle on front doesn't really move. I don't have access to AUX, but when I did a few months ago I hooked it up and had the same problem with noise being faint. I appreciate all the help from you fine folks! im new to this but I'm trying to learn and I'd rather fix it myself then sacrifice my pride and the opportunity to learn by taking it to the technician. Heres pictures of the project thus far
IMG_1187.JPG IMG_1188.JPG IMG_1186.JPG IMG_1189.JPG
 
Is this unit missing a heatsink for those " chip amplifiers" ? Don't operate this unit with out the heatsink..

index.php
 
pio_sx_680 said:
but when I turn on the radio, i can tune it to different stations but i have to put my ear up to the speaker to hear anything, and its often staticy when i do hear out of it.
Click to expand...
Are you using some kind of external antenna for FM ? That bar antenna on the rear panel is for local AM only.
 
avionic said:
So you swapped them around and nothing really changed ?
Click to expand...
If this is true. You have and issue with the pre-amplifier/switching circuitry.. Either a dirty switch , controls or combination of both. Or a failing component within.. Need to first give it a good Deox-it treatment to all the switches and controls.
 
avionic said:
There is only 1 Deox-it brand.
https://caig.com/
Click to expand...
okay ill check that out, and i switched the two original STK's around, and the noise was no longer faint.after switching and getting louder noise, i noticed that the amp at the top of the pic does not get warm and the amp at the bottom gets warm
 

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pio_sx_680 said:
okay ill check that out, and i switched the two original STK's around, and the noise was no longer faint.after switching and getting louder noise, i noticed that the amp at the top of the pic does not get warm and the amp at the bottom gets warm
Click to expand...
avionic said:
Is this unit missing a heatsink for those " chip amplifiers" ? Don't operate this unit with out the heatsink..

index.php
Click to expand...
 
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