Yes, there is, but on Donkey Kong, Junior and earlier cabinets, it's not hooked up on the monitor! On Popeye cabinets and later the control is hooked up.
On the monitor main board is a pot with a black shaft (VR403) which is the vert positioning pot. However it won't work if the jumper is not connected. Directly adjacent to the pot (to the right of it) is three shiny pins sticking up from the board close to each other. There may or may not be a white plastic connector with a jumper wire in it. If you're lucky and the connector is there then the control is hooked up and turning the black plastic shaft on the pot should move the picture slightly up or down. If the white plastic connector is not present then you need to jumper two of the three pins in order to activate that pot. Jumpering the middle pin to the pin closest to the edge of the circuit board should allow positioning the picture lower. Jumpering the middle pin to the pin farther away from you should allow positioning the picture higher up.
Example of the jumpering:
O
\ jumper
O
O
or
O
O
/ jumper
O
I use a cheap alligator jumper wire from Radio Shack like their number 278-1157 to jumper the pins. Be sure it is securely connected.