I have a philips N4450 tape recorder that was given to me by a friend. It's in really good condition. The belts were replaced before they disintegrated. My problem is it doesn't matter which fast forward or rewind button I press, it just fast forward. I? have replaced all the germanium transistors, checked all the diodes. Swapped the flip-flop boards and the tape tension boards. It will just not fast rewind. Any ideas?: