Hello, I have a Tascam Porta 02 which is not recording on tracks 3 and 4. Tracks 1 and 2 seem to be working fine. Tracks 3 and 4 do play audio correctly. I do not have the schematics, but I have done everything according to the user's manual. So far, no results. I have read that some re-capping may be necessary, but if anyone has any idea where to start, I'd appreciate it.