Assuming it's not a mechanical problem.
Looking here at the schematic seems the circuit along the ball count step up circuit is at fault.
Only see 3 points for fault,most likely the score motor contacts is the culprit.
Clean and gap as needed for all suspect within the path.

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Not sure if you have the schematics? here they are. >> http://mirror2.ipdb.org/files/2110/ShangriLa.pdf

Looking at your photo>>Left to right>>The switch you seek is starting from the left is your motor (2nd disc cam stack) ,1st set on the bottom of contacts from the set of three switching sets. ( as shown in the snip in my previous post)
Motor cam layout from your photo L-R >> is Index,cam 1,cam2,cam3,cam4,cam5,impulse,impulse.

Check you outhole and trough switch too.

A quick way to test and also mimic what issue you have is to lift the playfield up(remove ball first) score some points pressing a rollover or target which should activate the ball index relay,then press the outhole switch w/a wooden pencil and the ball count should step properly.
A way to mimic the ball count not working is to put a piece of paper between the score motors contacts to stop the flow of current on the way to the Ball count s.u. solenoid.
In order for this to happen after scoring points via a rollover /target and locking in the ball index relay first ,then add the paper in the score motor contacts (2nd cam from the motor position A contacts) and the ball count will not change.

Hey pindude80. Almost got it.
Did you look at the ball count unit itself? It could be bound up with gunk and not function correctly too.
A clean and lube should get it going.

Thanks,

Ok .

Ok ,(schematic 21f)You have to put points on it before the Ball count unit will step up,(basically a mulligan)until the Ball index locks in before it will operate after which its allowed to Step up to work and count each time the ball enters the outhole with small delay before being kicked over to the shooter rod. It will stayed locked until the last ball to game over. Check the Ball index relay and clean /adjust.
If that doesnt fix it ^^ try the following.
It seems that your first post showed it would happen at any ball,if thats the case then maybe the gap at the score motor cam is too close it seems. I had a similar problem with a Gottlieb and if the contacts were too close in the outhole switch that it would stay on the same ball occasionally,after i opened up the contacts gap it started to count correctly,maybe the same problem is happening on your score motor contacts. Assuming the wires at the termination points are soldered well and strong,see if that works.

Yes,^^that is correct, it will lock the index relay when points are scored until it goes into the outhole and then it unlocks till points are scored again which will allow the ball count step up to add but only after it is in locked mode. It wont lock in if points are not scored nor will the ball count advance either.
Sorry if i confused the way i described it prior post.

Looking at the coin unit and the player unit is what is between the score motor contact and the ball count step up relay, thats where i would look at next. See in the schematic snip on my first post. As it seems like everything else is working fine.

Looks to be the common feed to the coin unit (the blue-black tracer and the red-white tracer shown in the snip above)is what its showing going through to the ball count step up. Find the wires on the coin unit and see whats happening. Might also want to clean your jones plugs too as corrosion/crud could be the intermittent issue on the ball count.
As for the player unit it does not feed to the ball step up, the player unit is stepped through a make and break via score motor 2a.<<Was watching football and not reading that right when i posted before.
We are running out of things to look at.

2-3 turns approx.just enough to reset them.

Look at the contacts for the extra ball,
Could be a n.c. contact causing the problem.
Adjust and clean them, then make a score to close the index and pull the outhole switch.

Lets try this test first.
Ok it may be you have the torsion(return) spring too tight which will give the symptoms your describing.
If its too tight it does not have enough strength(the step up coil) to set to the next tooth(ball).
Here is what you want to do,unwind the torsion spring and put one turn on it.
Reset a game for 1 player. A quick way to do it with the playfield down is to press a rollover or target to lock in the index relay/put up points drop the ball in the outhole,let it kick over to the shooter lane,index locks/add points ,drop the ball in the outhole,let it kick over ....repeat till 1-5 ball to game over ,then reset it and see if goes to ball one. If it goes to ball one then there is enough tension.
If it does not go to ball one then with the torsion spring will need an additional turn to allow it to fully reset to one,try again ........

You said it would step up fine manually and the torsion(reset) spring works correct.
So when you put the ball in the cycle as described above,ball 1-5 game over did the ball sometimes take multiple times to step up to each ball?
On the ball count unit sometimes the drive spring gets a little slack in it and can not have enough umph to lock in the next tooth,but it can be altered by taking a few spring rounds (start with 1-2 is usually enough) and bending them off to the side and then reattaching it at the new spring loop location.

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On the post in red is where i am talking about bending the loops at.
* It may take a little time setting it but once you have it set it will work fine,trust me i had the same issue.

When you step the ball count up manually it does go to game over correct?

What is the difference between manual and electrically advancing?
Lets isolate the Bc unit.
Do you have an insulated alligator jumper wire? With the pinball unplugged attach the clip to the yellow secondary tap return,then with other end place it safely near the Bc unit step up solenoid.
On the solenoid you will see 2 wires,black which is the Hot feed and Red/white is the return path.
Plug the power cord in ,reset the game and with the insulated gator clip in a safe manner quickly tap the coil red/white tab and it should stop at each ball #.
It should step up each tap from 1-5 to G.o.
What are the results?

Ok

Do you hear/see the game over relay trip at that point? if yes continue on,if no skip to # 3
With machine unplugged.
1- Continuity check w/meter for the bulb. If bulb checks out ok,put it back into the socket base and check continuity this time with one probe to the socket base itself,with bulb completing the circuit use the other probe to the center terminal feed on the bottom of the base. If that passes then move to next step.
2- Power up the pin and reset ,advance/step up to game over.
Check for voltage when the game ends at the game over light,use your meter set for Ac voltage and touch one probe to the center terminal and the other probe to side of the bulb base,(careful not to short out) you should get a V reading.
3- If not then you will have to check your feed /return wiring of the game over relay/to the game over light not working or the g.o. relay itself,it could also be the contact/tracer on the ball count unit is not completing due to the b.c.u wiper fingers needing an adjustment,etc..... Clean and adjust.

Once you get the g.o. to light proper then we can move back to the ball count step up issue.

It's very easy to over look the obvious. I've been watching this thread from the beginning and learned alot of useful info, unfortunately, at your expense. Glad you got it fixed and back to playing. Pin-it should be writing trouble shooting tutorials and posting them.

Yeah that happens ^^,bulb quality (china/taiwan made) is lacking to say the least.

Lets narrow this down, back to the b.c.u. ▲ Try this with the playfield up,reset the game activate some points to set the ball index,then press(careful its live) the outhole relay direct(not the outhole switch itself) and what happens does it advance to ball 2? if so repeat for each till the g.o. lights. Did it count up correctly?

Very true.^^ Best to keep an open mind. ♪ ♫

Most things are simple...untill the human mind intervenes.

Or adult beverages!

So true.

Ok,Give the outhole relay a good cleaning (flex or file)and check leaf sw. gaps.
For some reason it works proper when you bypassed it using the gator clips direct ,now its a question of why its not getting the same voltage kick running through the circuitry (outhole switch triggers the (pulls in) ☼Outhole relay through☼Extra ball jack plug through☼Ball index relay through☼Score motor contacts 1-a through☼Coin unit and finally to the☼B.c.u. step up solenoid.
You said you dont use the extra ball feature,but as wizardblom pointed out it, could be you dont use it but it might be part of the problem in the circuit.

True^ we get what we pay for.

Unless they changed it in production and got rid of that feature,but seen here it says same player shoot again in the backglass which means an extra ball is given at some score or sequence.
A little hard to see but its there >> http://www.ipdb.org/showpic.pl?id=2110&picno=20171&zoom=1
On the schematic you can see in the G.I. (9-10/a-b section)the extra ball lite and shoot again lite wiring.
See what you can find and clean either the jack plug or extra ball relay if found.

Look under the playfield itself for the extra ball jack/relay,might be hiding there or in the backbox.

Not sure what that would have been for.^ Just make sure both are soldered well and tape them up good.
Does the score motor ever give intermittent operation?

The upper one is the service jack for the score motor(on /off),and the lower is for coin adjustment. 1-play for 10¢ or 2-play for 10¢ depending on plug position.

It works when you gator clipped bypassed it,maybe a relay is weak and not holding tight (extra ball or ball index) or the score motor contact gap is just a little off.

Maybe someone else can chime in here and see if we are missing something.

An extra pair of eyes via someone who has/had one is a good idea.
Seeing three others who have it.
https://pinside.com/pinball/archive/shangri-la/owners

Pm them and see who responds.

I was thinking maybe the machine is giving you the same player shoots again,maybe thats why its staying on the same ball.

Not questioning, just asking how it would know to do that without the spsa relay? Is it possible the wires that are tied together where the empty space is?

I don't think so, but don't know for sure. I would think the jones plug for the extra ball would only have 3 conections at most,IE; 1 for extra ball, 1 for credit, 1 for novelty.

I dont think the empty space on the mech. board is a missing extra ball relay.
As it would not either stay stuck on the same ball all the time since it is was bypassed direct,the clue i see is that it is random and to me it sounds like the E.B. relay is get activated either by vibration or possible contact continuity.

Looking more at the schematic it looks like if you lite up all three stars (red/white/blue) lites the special. Which is followed by 300 and center target.
It works by not allowing the ball to be count down via the E.B. relay not unlike a Make and break switch,if you see the snip at the top of this thread you can see how its a normally closed switch but will open when energized which tells me the contact of the E.B. relay is fault. Otherwise in order for the E.B to happen you must complete all the sequences to achieve it.

Seen here on the snips: When completed the E.B. relay pulls in when special sequence is completed then the contacts separate on the relay thus not allowing the Step up to occur which makes sense to what you are having.

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Link to Flyer and Schematic... http://www.ipdb.org/showpic.pl?id=2110&picno=4320&zoom=1

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