Yes, I'm not sure exactly when, but in the 60s United did switch it so the
pins tripped the Bank Relays and before it was vice versa..
If I'm not mistaken, on your machine the pin deck is attached to the head,
right? Pin switches are hot wired right to the Pin Relays in the Relay Bank?
Does some of the pins seem to pull their corresponding relays 100% of the
time and it's always the same few that have the problem?
I'd maybe first recheck the Pin Relays closed switches when the Pin Relays
are in the reset position.
With the pins made/up, stick a small screwdriver in between the what should
be closed switches in the Pin Relays that hadn't but should have energized.
If almost all 10 pins randomly have the problem, then we'll probably have
to consider other options. I'm sure you have, but carefully checking the switches
solder joints is always worth doing. I've seen jumpers that you swore were okay,
but come to find out, they weren't..

Hi. I'm thinking that most of the Pin Relays energize, so it's not a low voltage
problem unless a dirty contact in the #7 (and maybe others) Relay, but if it's a
contact, maybe one that's barely touching..
It's been a while since I worked on a Williams Shuffle from that era, but on
the pin deck, when a pin goes up, the make/break switches break the circuit
to the pin unit, then transfers it to the Pin Relay. If the 7 is up, and you elegator
clip the #7 pin contacts that are now making, the 7 Pin Relay should energize.
When it doesn't, with the elegator clip still attached, with a small screwdriver,
I'd make contact with the close switches in the 7 Pin Relay and check if touching
one of those sets energizes its own (7 Pin) Relay. With the elegator clip attached
(and the solder joints are okay), we know for sure the #7 Pin Unit make/break
switch on the Pin Deck is 100% making. If needed, you might want to bring
a jumper wire (an elegator clip on each end) with you and jump point to
point from going by the schematics. I made a jumping wire that's like 6 ft. in
length and it has come in handy..
Yes, it's common for certain Pin Relays to energize from other Pin Relays when
they get energized, including the 7 pin going up, but if the 7 pin (at times) doesn't
go up when it's the only one left when shooting a spare, then it wouldn't be from
contacts in other Relays. Only contacts within' itself..
What you'll have to do is run your hand over the pin rollovers (but not over the
last row of rollovers which energize the Shot Relays) until the problem happens
then make sure that set of switches (from the make/break) on the pin deck of
that pin is 100% making, then concentrate on its Pin Relay switches. If no luck,
then you'll want to follow that circuit's path from the schematic, and do some
jumping..

Yes, that's what I meant. I'm primarily into Ball Bowlers, but if I remember correctly,
the Chicago Coin's pin decks are attached to the lane, and yours to the head, so your
pin units are wired direct (no jones plugs) to the Pin Relays in the Relay Bank..
With the schematic and a little jumping, you'll probably catch the problem..