I have an official TI program recorder that doesn't appear to be working correctly. I've had it apart and cleaned it thoroughly before testing it. I've also tested all the pins on my interface cable. I think my problem is with playback, since it doesn't seem to matter what volume setting I use, I hear the same volume low hum either from the speaker or with headphones. I would assume that if playback were working then I would hear different volumes of tape noise.
Regardless, I don't have a prerecorded audio cassette to test my hypothesis with. I do know the TI-99 is putting out a signal when recording (tested on my PC). What things should I check to identify and perhaps fix this problem?