I have a Project Debut Carbon which is set up to an amp with a preamp. A few days ago a problem presented itself as only one of the speakers is loud enough, the other one being very quiet. If I disconnect the TT from the preamp and connect it to an aux by itself, both speakers work fine (except of course being both quieter than normal because a preamp is not present.) Can anyone please help me solve this? I resothered each colored cable near the RCA jacks but it didn't solve anything.
The problem is in either the phone preamp or the cable connecting it to the amp (if it's an external one.)
If you have a preamp - power amp system and the phone preamp is built in to the preamplifier then the phono section in that can be bad without affecting any of the other inputs.
By the way a phone preamp does more than just amplify the output of the cartridge. It applies the required RIAA EQ that is needed to listen to all records.
Then one channel the phono preamp is bad. You don't say what make and model it is?
Can't say for sure but the black wires are likely to be the minus or ground and the colored wires the positive leads.
A broken wire is usually easy to see.