(Topic ID: 207922)

GTB Target Alpha fault

By Vintage-Pinball

6 years ago


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    Target Alpha player unit (resized).jpg
    cropped_TA-1.pdf (PDF preview)

    #1 6 years ago

    Here's an odd one for you: I've a Target Alpha that has a random fault.
    Basically, and irrespective of how many players are selected, the machine sometimes goes to the next ball in play. This happens when the ball only hits either pop bumper, nothing else. The relay that controls the pop bumpers is fine, cleaned and adjusted with no change. Ive got a schematic on order but in the meantime, does anyone have any ideas as to why this is happening?
    Thanks in anticipation

    #2 6 years ago

    Next ball in play is a function of the player unit. Even on multiple players is skips a ball ahead? If it sometimes pops to the next player... then your trough switch could be gaped a little tight. With your fist pound on your pf and see if the impact will cause this. Regardless check the trough switch.

    #3 6 years ago

    So, as soon as it hits a pop bumper it skips ahead? Drain or not?

    Check the whole sequence around the 100s relay (M). B, the pop bumper relay, is involved there. And check the rivets on the Player unit for cleanliness and good contact. Give a light sanding with 600# and then a drop of light oil.

    cropped_TA-1.pdfcropped_TA-1.pdf

    #4 6 years ago

    Thanks for your replies.

    1/ I tried thumping the top of the playfield but it makes no difference. Ill check the trough switch too though.

    2/ Its a random thing, and only when a pop bumper is hit. The ball can really pound a pop and all is fine, then i hits it just once and will then advance to the next ball. I'll try the player unit check though and see what happens.

    Thanks again.

    #5 6 years ago

    I've seen an odd problem on "Target Alpha" before where it adds points to another player's score, usually when the ball is about to be kicked out of the outhole into the shooter lane.
    I read about a fix for that, but it was a long time ago, and don't remember where I saw it. It sounds like a related problem.

    #6 6 years ago

    Does the motor run when this happens?

    #7 6 years ago
    Quoted from HowardR:

    Does the motor run when this happens?

    I need to check, Howard. The playfield is down, obviously, during play so I'll get someone to look through the coin door to watch as its being played and see whats going on.

    #8 6 years ago

    Hi Classicpinballs
    random faults are non-pleasing - does it happen rare or seldom or sometimes or often or most of the times ?
    When it happens rare or seldom or sometimes: I like to use a Test-Light - but I actually play --- the Test-Light is connected "parallel" to a "Relay in question" --- one side of the Test-Light is connected to "one side of the coil on the relay" - the other side of the Test-Light is connected to "the other side of the coil on the relay" - with this: EVERY TIME the relay gets (faulty) feeded by current - the Test-Light also lights-up. There are looooong wires on the Test-Light - I have it clipped-on at the coil - looooong wires - I can take it through the open coin-door out and lay it on the apron --- I have the playfield down and I PLAY - and have an eye on the Test-Light --- IF (if, if) the Test-Light ALWAYS lights-up when the fault happens: I am allowed to clue: The fault is in the feeding-line to the RELAY.
    SteveFury made an Test-Light - see here https://pinside.com/pinball/forum/topic/reading-gottlieb-schematics#post-2634425 - two car bulbs of 12 Volts put one behind the other sums up to "Test-Light of 24 Volts".

    Make Yourself such an Test-Light and hook it onto "Coil of P-Add-Player-Unit-Relay" - then play --- does the Test-Light ALWAYS lights-up when the fault happens ?

    May want to try "quick and dirty test" --- the pin is started and some points are made --- bang with Your fist on the wood NEAR the P-Add-Player-Unit-Relay - does the fault shows up ? Greetings Rolf

    #9 6 years ago
    Quoted from Vintage-Pinball:

    I need to check, Howard. The playfield is down, obviously, during play so I'll get someone to look through the coin door to watch as its being played and see whats going on.

    Or you may be able to hear it. Or you could attach wires from the motor to a light bulb outside the front door.

    #10 6 years ago
    Quoted from HowardR:

    Does the motor run when this happens?

    This will be important to understand but I'll assume that the score motor is running because it takes multiple steps of the player unit (and therefore multiple pulses from the score motor) to advance to the next ball from all players except player 4. If the problem happens and the remaining players' lights flash in order (player 2, then player 3, then player 4) and you end up with player 1 on the next ball, that would indicate that the score motor is running.

    But either way it will help to eliminate some of the possible paths that may be advancing the player unit.

    Target Alpha player unit (resized).jpgTarget Alpha player unit (resized).jpg

    Try blocking switches with a piece of folded paper and playing the game for a while to see if the problem persists. Start with the switch on the AX relay highlighted in red. You may need to add the paper after the game has reset and started a new game. If the problem persists that would eliminate the paths through the S and P5B switches.

    Then remove the paper from the AX relay switch and use it to block the switch on the P relay after the game has started. You may need to keep the ball from draining. If the problem persists that eliminates the paths through the coin unit.

    If neither of these experiments change anything you may need to start tracing wires along the paths to the Add Player Unit solenoid looking for frayed wires, bent solder tabs, solder blobs, etc.

    /Mark

    #11 6 years ago

    Success! I went through your replies and tried the various ideas. The fault was a couple of frayed wires on Add player unit. I could see them at first until my mirror showed them up, underneath the wire itself so not immediately visible. Just 2 little strands were giving me the hassles.

    Many thanks everyone!

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