Akai four track reel to reel won't record though vu meters say it is.
The vu meters only show that there is an input signal. The meters do not mean the deck is actually recording. If the deck will play a previously-recorded tape, how well does it sound? if the sound quality is muffled or very low, the play-back heads are dirty. If the playback heads are dirty, then the erase and record heads are too. In the tape path, the direction your tape moves from supply reel to takeup reel determines which heads are in which order. Most R-to-R decks play from left reel to right reel. The magnetic heads are in this order, with the the arrow indicating tape transport direction:
Supply Reel moves tape across > Erase head first, then across > Record head second, then across > Playback head. Some machines use the same head for record and playback, but no machine uses the erase head for anything but erasing pre-recorded material on the tape.
First, using tape recorder head cleaner or rubbing alcohol, clean the erase head (the first one the tape moves across) thoroughly with a Q-tip. If the heads are VERY dirty, use a pencil eraser AND the Q-tip. If this head is not clean, it will either not completely or not at all erase the material already on the tape. If the tape isn't erased, you either will get your new recording laid over the top of the existing one and it will sound like gibberish, or the new recording will not be recorded at all, and the original recording is all you will hear. Next, clean the second head the tape passes over. Usually this is the record head. If it is dirty, it will not record clearly or at all the material you are trying to record. Last, if there is a third head (most decks have this), clean it thoroughly as well. This is the playback head, and if it is dirty enough, you will hear nothing, although your new recording may very well have been laid down on the tape. Always clean all tape heads at the same time; in other words, don't just clean one head and not the rest of them. Clean all tape deck heads AS WELL AS the capstan (skinny metal pin that rotates) and pinch roller (the rubber wheel that 'pinches' the tape between itself and the rotating metal pin) thoroughly, rethread your tape through the head array, capstan, and pinch roller onto the takeup reel, and see what happens. If everything is clean and you still don't get any playback of your recording but you do get playback of pre-recorded tapes, then the problem is in the record circuit, and can be anything from faulty input stages to a bad head--deck heads DO go bad, although not often. If this is what happens, you have to take the unit in for repair by a qualified technician.
