It sounds like it is, yes. My Flipper Parade often gave 6 or more balls on starting a new game. I cleaned the BCU stepper and it was fine afterward.

To me it sounds like either the stepper is getting stuck and sometimes not making it all the way back to 5 balls (or I suppose it could be a problem with the disc itself), or else the coil isn’t getting the right number if pulses to get it back to 5 always.

Have you serviced the stepper unit including the disc?

Can you have someone press start while you observe the coil to see if it’s pulsing enough times but not moving? If it’s pulsing not not moving freely I’d say you have a mechanical issue with the stepper. But if it’s not pulsing enough then there’s something wrong in the circuit and you’d want to look at the schematic at whatever causes that to reset (could be a score motor switch).

Hi Playdium
I would look along the "marked green" wiring. Greetings Rolf

0Playmates-pinside-snippet-Work-01 (resized).jpg

For my own education, why is the path you marked green correct and not the one OP marked? Still learning schematics. Thanks, Rolf!

Hi goldenboy232
Playdium writes in post-1 "upon startup the game" --- ipdb tells us the pin is an (true) Add-A-Ball-Pin. Playdiums "red line" has a switch on a relay (maybe "E"-Relay) the Score-Motor-Switch-1C is drawn closed means closed when the motor does NOT run --- when starting a game the motor DOES run.
Along my "green line" we see "DB-Armature-Switch" --- the word "armature always has to do with "starting a game".

I wrote about xsvtoys and SteveFury - want to read this: https://pinside.com/pinball/forum/topic/first-time-em-several-question-marks#post-4282958
Greetings Rolf

Wow those are WORN in that last photo.

Hi Playdium
please do net get angry --- one thing is "we should use the proper words" - in post-1 You write "(problem BCU) randomly resets to 5 balls, or 4 or 3". I think the words "reset, resetting" are used when the Unit is stepped 5,4,3,2,1,Zero ball(s).

In post-8 You use the words "high power" --- the stepping up and the stepping down the BCU is done with 24VAC. See the first JPG --- encircled burgundy-red: Score-Motor-Switch-1A. In the schematics Aquarius we see the "Timing Chart" - SCM-1A closes the switch FIVE times in the period of time when the motor does turn a third of a revolution --- the stuff to actuate the motor-switches is there THREE times --- the motor is 120-degrees symmetrical. I doubt that THREE times there is the same fault "actuating BCU for the fourth and the fifth time".
MAYBE (maybe) - see in the JPG my red line and the question mark: Maybe the DB-Relay is resetted too early - so fourth and fifth pulse from SCM-1A are suppressed ? Watch the DB-Relay and listen to the sound of the motor turning - DOES DB-Relay resets VERY late in the turning of 120 degrees - almost at the end ?

See the second JPG - a picture "Gottlieb King of Diamonds - taken from somewhere in pinside" --- see my green line to the spring wound around the axis. IF (if, if) the spring is tightened when stepping Zero,1,2,3,4,5: Maybe the spring is tightened too much for the steps 3 to 4 to 5 ? Remember the original setting - unhook the spring - loosen a third or a half or a full circle - hook-in again the spring - then try the pin - any better ?

I watch Your video - I do not see a stepping - I do not see something of help me understanding - please write an explanation "first we see ... then we see ... then the camera is turned and we see ... etc." I do not understand the video --- well I am NOT good in Single-Player-Pins - due to the fact "such pins are ultra-rare in Switzerland". Greetings Rolf

0Playmates-Work-02 (resized).jpg

0Playmates-pinside-picture-King-of-Diaomonds (resized).jpg

Hi Playdium
in the first JPG in Your post-8 I see a wire "orange-green" - also I see a wire "yellow-red maybe the colors are mingled" --- in Your snippet of schematics in post-4 look for "Coil on Subtract Ball Count Unit" then look rightbound --- Switch "Ball Count Unit" with these wire-colors.

When You want to learn about "white, red, black wire" on the unit, shown in post-8: You must look all over Your schematics for "some word(s) and Ball Count Unit" - then look at the wire-colors. OR: You show more of the schematics. Greetings Rolf

Hi Ken
I believe we are on the problem You mentioned in post-1 - randomly NOT stepping up to five balls when starting a game (?).
HowardR lately showed his good invention --- an Jumper-Wire or an Test-Light --- one end has an (conventional) gator-clip (to clip-on the Jumper-Wire / Test-Light at an easy accessible Solder-Lug on an switch (we want to clip-on)) --- the other end of the Jumper-Wire / Test-Light ends in an Safety-Pin. The insulation around wires in pinballs is made of fabric --- we insert (sideway - almost parallel to the running wire) - we toggle-off the pin, unplug the main power cord (Safety Reasons) - we insert the safety-pin end of Test-Light-Wire into a wire about 2 to 3 inches away from a solder-lug - insert into the wire - as it is impossible to clip-on there an gator clip. Examples of such "impossible to clip-on an gator-clip are "Score-Motor-Switches" or Relay-Bank-Switches" - not enough room for a gator-clip to clip-on.

See the JPG - I wonder if (encircled burgundy-red) motor-1A switch TRUELY closes five times in a turn of 120 degrees (?). To test this: See my drawn yellow Test-Light*** - one side is clipped-on somewhere at the abundant Wire-Black (my example is: Coil on Add 1000 Unit) --- look for an Coil having two wires of color Black soldered-on at one solder-lug on the coil. The other side with the safety-pin end: Insert the safety pin 2 to 3 inches away from motor-1A-Switch into its wire-color-orange-yellow. The other blade of this switch has an wire of unknown color soldered-on - BUT the wire of unknown color is also soldered-on at "Through-Switch***" - "Through-Switch***" has wire of unknown color and wire-orange-black --- check the Through-Switch for the color unknown - look for same color on motor-1A-Switch - insert the safety-pin of the Test-Light on motor-1A-Switch into wire-color-orange-yellow.
Then plug-in, toggle-on, start a game: DOES the Test-Light ALWAYS light-up FIVE times when the motor does a turn of 120 degrees ?

"Through-Switch***" - here http://www.ipdb.org/showpic.pl?id=1828&picno=39631 in the upper right corner of the pic is the Through-Switch*** - the ball kicked out - rolls over to the shooter-alley and by rolling over: Closes the Through-Switch***.

Test-Light*** - @Steve-Fury made of two 12Volt-car-bulbs put one behind the other his 24Volt-Test-Light - he shows it here: https://pinside.com/pinball/forum/topic/reading-gottlieb-schematics#post-2634425

I would like to know "DOES the Test-Light ALWAYS lights-up FIVE times when the motor is doung a turn of 120 degrees (a third of an revolution) ?" Greetings Rolf

0Playmates-Work-03 (resized).jpg

Hi Ken
thanks for the videos - unfortunately when I play them "the video kind of "freezes" - then jumps to another position. Unfortunately the lighting up of the Test-Lamp is very fast - hard to count.

In post-17 You write "motor 'randomly' turns 1/3 or 2/3 or 3/3 of an full revolution". (((Williams and Bally have 180 degrees symmetrical Score-Motors))) Gottlieb Score-Motors are 120 degrees symmetrical. The "unit / entity" is 120 degrees turning (among other stuff done): Five times the motor-1A-Switch is actuated when the motor makes a turn of 120 degrees.

In an fully running gottlieb it depends - the 1/3 or 2/3 or 3/3 depends on "is it complicated / time consuming when the pin does reset the Score-Drums".

Maybe I chase an fantom - my idea is: One of the three symmetrical 120 degrees actuates truely five times the motor-1A, another of the three symmetrical 120 degrees actuates (faulty) only four times - the last of the three symmetrical 120 degrees actuates (faulty) only three times.
The use of the Test-Light is tricky - another idea - when the pin is toggled-off: Mark with some paint - one dash - mark one of the Home-Positions, aother Home-Position mark with two dashes - the last Home-Position mark with three dashes.
Play - start new games - do this about 10 to 20 times - keep a record of "after the game has started and then the pin idles - motor no longer turns: Stopping on Position "one mark" the Ball-Count-Unit has stepped X steps --- stopping on Position "two marks" the Ball-Count-Unit has stepped Y steps --- stopping on Position "three marks" the Ball-Count-Unit has stepped Z steps --- big question: Is it totally random or do You see a pattern like (just as an example) "one mark gives Ball-4, two marks give ball-5, three marks give ball-3" ? You can prove my theory right or You prove it wrong. Greetings Rolf

My guess, for what it's worth as I'm newer to this hobby, is that your heavily worn wiper fingers are getting caught on worn rivets (each was designed to be rounded for smooth action - attached pic has lightly worn wipers on left and brand new on right). I would recommend replacing with new wiper fingers, grinding smooth the heavily worn rivets (or ideally replacing them as well) and very lightly wiping path with Teflon lube. As a temp hack, while you're waiting for new wipers, you could try to grind what's left of your wipers into something that resembles the rounded shape of new ones.

image (resized).jpeg

If could just be age, but in addition when an electric current flows through a coil it has something similar to the momentum that a mass has. When the circuit is interrupted, that electrical "momentum" has to go somewhere and can arc across the interrupting contacts. Some games have resistors (or diodes in DC circuits) to keep arcing to a minimum.

For a more technically correct description, look at these threads:
https://pinside.com/pinball/forum/search?s=1&what=posts&q=resistor+arcing&topic-machine=&pinsider=&age_days=&subforum=63&sort_by=date&sort_order=DESC#results

Did you send the contact plate to PBR to have the rivets replaced?

Jody

PBR also has NOS BCU discs for $15.