Laney BC 120 not working

[Ronjon]

Recently I came across a broken Laney BC 120 amp. The unit powers up and when I send audio signal (CD music) through the Active or Passive input, I get low volume distortion and none of the controls (gain, bass, treble, volume, eq etc) work.

I read a gentleman with the username, oc disorder who posted a beautiful trouble shooting scheme back in 2014 for a BC 120 (http://music-electronics-forum.com/t37745/). Can anyone please help troubleshoot this amp? I alway wanted to troubleshoot a circuit board and perhaps this will be my first one!

Thank you!

[J M Fahey]

Start by searching for and posting the schematic here

[xtian]

Plug your CD audio source into the FX return on the rear panel. Sound OK?

[Ronjon]

Start by searching for and posting the schematic here

Ok. Thank you. I believe the following link’s page 2 and 3 has the schematics. I am not sure of page 2 however. The label says 9057_3 instead of 9057_2 that I see on the PCB that I have.
http://music-electronics-forum.com/a...bc120range.pdf

[Ronjon]

Plug your CD audio source into the FX return on the rear panel. Sound OK?

Thank you for the suggestion! It seems like I may have bad contact on the PCB. The FX return and other inputs sound fine using the head phone jack. I haven’t hooked up the cabinet speaker yet. I will get back to you confirming that tomorrow. Thank you and have a good night!

[Ronjon]

Very odd! Now the amp is working flawlessly. I am certain hooking up correctly and testing it and found problem and now there is no issue with it. Thank you again for your encouragement and guidence. I wish you guys all the best.

[g1]

See the sticky post about switching jacks at the top of the "Maintenance" section. Most likely connecting to the FX return jack gave it a bit of exercise which cleaned or 'deoxidized' it. It is used to route the signal through from the preamp to the power amp section.

[Ronjon]

See the sticky post about switching jacks at the top of the "Maintenance" section. Most likely connecting to the FX return jack gave it a bit of exercise which cleaned or 'deoxidized' it. It is used to route the signal through from the preamp to the power amp section.

Thank you for your kind note. I did not know this problem! Plugging in and out a 1/4” must have cleaned the contacts. This was a blessing in disguise.

Thank you xtian.

[The Dude]

You should still clean the jack contacts with some contact cleaner for reliability. I wouldn't trust the amp to stay working otherwise.

[Ronjon]

You should still clean the jack contacts with some contact cleaner for reliability. I wouldn't trust the amp to stay working otherwise.

Yes, I will do that as soon as I get some contact cleaner. Thank you for the warning!