Found this in an old thread:
Conion c100
tape 1
FBM 9.6
SBS 8.9 x 2
From what I remember, one of the 8.9's was a little too big (or was it too small?), but these sizes are very close. I'm pretty sure the flat belt size is dead-on.
Did you check the pin connector near the front, in the middle of the box on the top board? It's hard to see with just the back case removed. That one gave me a lot of trouble in the beginning of my resto. If it's not the culprit, you may need to remove the board and search around for a loose solder joint. Several months after I finished the C-100, I had a solder joint on a transistor start to let go, causing the "machine gun" effect.
You will need to remove the chassis to remove the board, but the chassis needs to be removed to properly clean the pots and switches anyway.
Here's the connector that gave me trouble. The arrow is pointing to the connector between the switches.:
Help.jpg