I just picked up a 917-1 and am having several problems with it. No matter how many coins are played, the line unit always steps up to the maximum after the first coin is played. If I manually reset it, it will immediately step back up to the max. Is this normal?
not normal.
there's a "pay detect trip relay" and a "j.p. detect trip relay". If either of those is tripped, you'll have your line unit issue.
looks like both of those are electrically reset, so they will look like a pair of coils at right angled to each other operating a shared switch stack.
From Maurice's 917 pics, they are on the edge of the top insert panel.take a look and see if one is tripped (usually that means the switch stack is down). If it is, manually reset it and see if the problem goes away.
the pay detect trip relay resets via the same wire as the line unit, so if the line unit is resetting but the pay detect isn't, it could only be the reset coil itself, the wire, or it's resetting but tripping immediately. The reset pulse comes from a line unit '0' switch. The '0' is one of the ones poking out over the white plastic ratchet on the line unit and gets shoved open by the white pin when the unit resets. You'd want to check the switch with the wire going to the reset coil lug ... schem says it's grey/red and a wire segment goes to the pay detect trip relay reset coil.
fix the line unit issue first and if it's the pay detect trip relay, that may change the payout behavior. If still not working, then pick whether you want to debug coin or credit play and we can go from there. The game has diodes all over the place, so some techniques for payout testing won't work.
do you have a voltmeter / ohmeter / jumper wire?
I split your post into a new topic so more people are likely to look.