The first thing I did was replace the rubber belts as these tend to lose elasticity or sometimes deteriorate alltogether. After doing that I encountered a strange thing. The cassette player was in record mode despite the record switch not being engaged. I discovered that when I had it apart I did not have a hook placed inside the record switch loop, thus the switch could not change state. Once that was fixed it worked perfectly.
The first thing I decided to try it out on was on my TRS-80 Model 100. After adjusting the volume and tone, I was able to get the computer to successfully read and write to a cassette tape.
After that, I tried using it with my PC-1 Pocket Computer. After some further minor adjustments, it seemed to work just fine. Now I can save any BASIC programs I type in onto tape.
Now that I have proven that it works as a storage unit for computer programs, I can use it on my MIL Mod-8.
A few months ago, I had a modified Mod8-6 board with cassette interface made up so that I could experiment with Robert Swartz's MIL cassette solution. So far I haven't been successful. The code clearly writes data to the tape, however when it is read back, it doesn't match. There is some troubleshooting left to do on this.