Hope this will be an easy one for the electronics techies... I have only the most basic knowledge of electronics, but can solder!
So, my Clean channel stopped working as follows... There was a loss of tone over a period of months, and then the volume faded away, until I now only have a very, very faint audio on both clean and boost channels when plugged into the front jack.
What is the most likely component on the clean channel input circuit to fail and cause the lack of input amplification ?
Diagnosis to date:
Visual inspection
- There are no signs of any blown caps or burnt resistors or solder cracks.
- the PCB is clean and in good condition
- the audio is still good if I plug my guitar pedal directly into the Effects Return jack.
When plugged into the front jack:
- the clean channel has extremely low, very faint volume.
- The controls on the clean channel seem to have no effect, but its hard to tell.
- The channel switch and LED between boost and clean channels functions OK , but ...
- the Boost channel is also extremely low volume, (probably because its getting such a faint signal from the clean channel??)
- the Boost channel controls seem to function as they should on the faint signal.
- I also noticed that some of the Boost Channel and the reverb control create a soft buzz when touched.
When plugged into the Effects Return jack:
- the sound is good and full volume, so I can use the amp simply by plugging my guitar pedal directly into the Effects Return jack.
- but of course none of the tone and volume controls have any effect when plugged into the Effects Return, so I really want to try to get the clean channel control circuits working again.
Intended repair steps
- replace the IC chip on the clean channel circuit?
- test and replace Caps
I am really hoping that it will just be a matter of replacing IC chip on the Clean channel circuit...but don't really know if that's the component most likely to produce these symptoms.
Can any electronics fundi's please give me some basic guidance on where to start.
Thanks in advance.
Huntly
So, my Clean channel stopped working as follows... There was a loss of tone over a period of months, and then the volume faded away, until I now only have a very, very faint audio on both clean and boost channels when plugged into the front jack.
What is the most likely component on the clean channel input circuit to fail and cause the lack of input amplification ?
Diagnosis to date:
Visual inspection
- There are no signs of any blown caps or burnt resistors or solder cracks.
- the PCB is clean and in good condition
- the audio is still good if I plug my guitar pedal directly into the Effects Return jack.
When plugged into the front jack:
- the clean channel has extremely low, very faint volume.
- The controls on the clean channel seem to have no effect, but its hard to tell.
- The channel switch and LED between boost and clean channels functions OK , but ...
- the Boost channel is also extremely low volume, (probably because its getting such a faint signal from the clean channel??)
- the Boost channel controls seem to function as they should on the faint signal.
- I also noticed that some of the Boost Channel and the reverb control create a soft buzz when touched.
When plugged into the Effects Return jack:
- the sound is good and full volume, so I can use the amp simply by plugging my guitar pedal directly into the Effects Return jack.
- but of course none of the tone and volume controls have any effect when plugged into the Effects Return, so I really want to try to get the clean channel control circuits working again.
Intended repair steps
- replace the IC chip on the clean channel circuit?
- test and replace Caps
I am really hoping that it will just be a matter of replacing IC chip on the Clean channel circuit...but don't really know if that's the component most likely to produce these symptoms.
Can any electronics fundi's please give me some basic guidance on where to start.
Thanks in advance.
Huntly
