Lasonic TRC-931- No stereo sound when using RADIO function, but MONO works as it should with both speakers...

[Myklejay]

I have a Lasonic TRC-931 (MKII) that works well, except for no STEREO sound while using the RADIO function.

1) When RADIO function is selected, with STEREO selected, I only have sound in the left channel, with very low (almost non-existent) sound in the right channel with the volume turned up, balance works.
2) When RADIO function is selected, but with MONO selected, I get sound on both left and right channels at equal volume, and balance works.
3) When the AM/FM switch is rocked back and fourth several times quickly, the FM sound becomes very distorted on the left channel when STEREO is selected. The distortion goes away when switched to MONO. (makes me think that this AM/FM selector switch may be the culprit)
4) I have perfect STEREO and 2 channel MONO sound with all other functions on the box. (tape, phono, aux)
6) When headphones are plugged in, I get the same symptoms as playing through the speakers (no stereo sound with RADIO function, all other functions have STERO sound)
7) The box also has a "ground loop" type buzz that gets louder when the volume knob, or really anything metallic on the left side of the box is touched. Crazy thing is, when the A tape deck EJECT button is touched, the buzz goes away completely...(not sure if the two issues are connected or not)

I have taken all boards out, looked them over for anything obvious, and have thoroughly cleaned out all pots and switches with Deoxit D5. This did not help the issues noted above.

Any suggestions to help sort out these issues would be greatly appreciated!

 

[SparkyChef]

I have a Lasonic TRC-931 (MKII) that works well, except for no STEREO sound while using the RADIO function.

1) When RADIO function is selected, with STEREO selected, I only have sound in the left channel, with very low (almost non-existent) sound in the right channel with the volume turned up, balance works.
2) When RADIO function is selected, but with MONO selected, I get sound on both left and right channels at equal volume, and balance works.
3) When the AM/FM switch is rocked back and fourth several times quickly, the FM sound becomes very distorted on the left channel when STEREO is selected. The distortion goes away when switched to MONO. (makes me think that this AM/FM selector switch may be the culprit)
4) I have perfect STEREO and 2 channel MONO sound with all other functions on the box. (tape, phono, aux)
6) When headphones are plugged in, I get the same symptoms as playing through the speakers (no stereo sound with RADIO function, all other functions have STERO sound)
7) The box also has a "ground loop" type buzz that gets louder when the volume knob, or really anything metallic on the left side of the box is touched. Crazy thing is, when the A tape deck EJECT button is touched, the buzz goes away completely...(not sure if the two issues are connected or not)

I have taken all boards out, looked them over for anything obvious, and have thoroughly cleaned out all pots and switches with Deoxit D5. This did not help the issues noted above.

Any suggestions to help sort out these issues would be greatly appreciated!

Hey all, recently got my Lasonic TRC 931, got it fired up and am experiencing the exact same issue as Myklejay as well as a non functional power switch. New to this any any help/advice is appreciated (also looking for parts, need buttons for the B tape deck, a know for the function switch and possibly a mic select switch) tia
SparkyChef

 

[hopey]

Try moving the audio cable attached to the tape head this can be the source of the ground loop, you can separate the cores where it terminates at the PCB.

7) The box also has a "ground loop" type buzz that gets louder when the volume knob, or really anything metallic on the left side of the box is touched. Crazy thing is, when the A tape deck EJECT button is touched, the buzz goes away completely...(not sure if the two issues are connected or not)

Yes its sounds like the FM mode switch, need to pull down and clean internal contacts. You may have to remove from PCB.

3) When the AM/FM switch is rocked back and fourth several times quickly, the FM sound becomes very distorted on the left channel when STEREO is selected. The distortion goes away when switched to MONO. (makes me think that this AM/FM selector switch may be the culprit)

 

[SparkyChef]

Try moving the audio cable attached to the tape head this can be the source of the ground loop, you can separate the cores where it terminates at the PCB.

7) The box also has a "ground loop" type buzz that gets louder when the volume knob, or really anything metallic on the left side of the box is touched. Crazy thing is, when the A tape deck EJECT button is touched, the buzz goes away completely...(not sure if the two issues are connected or not)

Yes its sounds like the FM mode switch, need to pull down and clean internal contacts. You may have to remove from PCB.

3) When the AM/FM switch is rocked back and fourth several times quickly, the FM sound becomes very distorted on the left channel when STEREO is selected. The distortion goes away when switched to MONO. (makes me think that this AM/FM selector switch may be the culprit)

Thanks for the response, I'll give that a try!(and report back)

 

[Hajidub]

Thanks for the response, I'll give that a try!(and report back)

His advice was for the sound, what's weird is my Lasonic power button just stopped working (after working fine and no use). I need to take it apart and see if the spring lock gave up.