“Hello everybody. I recently purchased a Pro-One, so keeping this is a bit redundant. I have had tons of fun with this little guy. I bought him to learn synthesis, since I am primarily a guitar player. All of the knobs and switches on this unit have proved to be great fun. Trigger the Sample and Hold with a drum machine, and you will be right pleased. This unit sounds great. There are absolutely no scratchy pots of faders. Everything works.
Things worthy of mention include the following:
1- Though there are no missing screws for the back-plate, sometime in the past somebody must have tightened two of the screws too much and cracked the fragile plastic pole pieces. The screws are still there, they just spin and spin. On a positive note, they are really of no importance and the back-plate stays solidly in place.
2- The battery cover is cracked, but manages to stay in place. Do not ask me how, it just does. I do not understand it.
3- The silver “Hold” button was replaced last month. It was working intermittently. Now it works perfect every time.
4- I had a 10 turn trim pot installed in the VR-7 position to make for easier and more accurate adjustments of the tuning and scaling. It is the blue squarish looking device by “VCO Tune”.
5- Being an older analog synth, the tuning/scaling does tend to drift depending on how long you have had the unit on, your power supply etc. Since I used this mainly for bleeps and bloops, it really never bothered me. If you are playing some Chopin Concerto with an orchestra and need ultra precise intonation, then you may have a problem on your hands.
6- Power switch was replaced for greater tuning stability. The original power switches have an issue that if you tap around them, the tuning dances around. This unit does not exhibit this problem.
7-The modulation grip needs two thumb screws in order to connect. Nothing fancy. Should be easy to find.” Link