25 year old 6 speed shimano derailleur

[relnes]

I have an old bike I'm trying to rehab to give away. It has a Shimano 6 speed front and rear derailleurs that has POSITION FH adjust stamped on the front. Through a square hole in the face of the derailleur you can see an adjustment screw. From the rear of the derailleur you can see another screw. There is no notation as to what function they perform. It doesn't seem to have a barrel adjuster or anything marked as high and low limit screws. The derailleur cable is secured by a hex nut rather than a hex screw. I'd like to find information regarding setting the high and low limits as well as how to adjust derailleur cable tension. The front derailler does have the limit screws marked clearly. I have images attached if anyone thinks they can help.
Thanks
Rick

[xerxes]

At a guess, I would say that the one on the front is the high gear limit stop. Try turning it clockwise, you shold see the derailleur move slightly inwards and back outwards when you turn the screw anticlockwise.

Are the gears indexed, or are they just a friction shift? If they are just friction they don't need a barrel adjuster.

The derailleur will be in the highest gear, smallest sprocket, when there is no cable tension. So to set up the limits and the cable, first loosen the cable clamp bolt so that the cable is free, then set the high limit so that the chain runs smoothly in the highest gear, but cannot come off the smallest sprocket. Pull the cable through the clamp bolt so that its taught enough to not flap about against the frame, but not so tight that it alters the derailleur position and tighten clamp bolt. Next adjust the shifter so that the derailleur is in the lowest gear, biggest sprocket, and set the low limit so that it runs smoothly, but can't go too far and off into the spokes.