Your problem is probably incidental to your cleaning.
You need to systematically start with the inputs connectors. Are the outputs of the Teac going to the inputs of your preamp? If so, try switching them what you think are the inputs of the Teac (sometimes the labeling can be confusing).
Also, try working all the switches in the signal path back and forth a couple of times to be sure they're engaging correctly. You could have a broken switch or iffy contact that has to be played with a little.
IIRC, you were getting stereo out of it before but you said it didn't sound very good. Are you sure that the selector switch is set to tape and not source? Could you have engaged record by accident? If so, then you may have erased the sound on the tape you're using to test the machine. Do you have another tape to test it with?
If not, hook it up to something and try recording something with it. While it's recording, switch between "Tape" and "Source" . There's also an output volume pot. It should be set at around one oclock.
If you don't have one, it's a good idea to get your hands on manual. You can download one for free here;
http://www.hifiengine.com/manuals.shtmlYour machine is particularly complex. You really need to spend some time with a manual to know the right settings.
In other words, relax and take your time learning this stuff. It's very unlikely that you've done anything that pushing the right button(s) won't fix.