(Topic ID: 298634)

Firepower sling locking on

By robm

5 months ago


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  • 25 posts
  • 6 Pinsiders participating
  • Latest reply 5 months ago by Schwaggs
  • Topic is favorited by 1 Pinsider

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#1 5 months ago

Have a Firepower that has the right slingshot locking on. It has a rottendog MPU/driver combo board installed that has been working fine for months.  I had to replace a fuse after the first time.

So coil resistance and diode tested OK, so i pulled the board out and replaced the drive transitor (q10) with an IRL540N.

Still the same - coil was locking on.

So then replaced the coil with a new one and new diode, and its still locking on.

However its a little strange in that the coil doesn't lock on at power up, only after the ball shoots into the shooter lane after a game is started. It also locks on when i go into the coil test.  I've also tested the slingshot switches with a multimeter and they test fine (ie: switch isn't closed).  I also have tried starting a game (it takes a couple of seconds to kick the ball out), and pulling the switch input switches (2J2, 2J3) from the board and the sling still locks on.

So it seems to me that maybe when the fuse blew the first time, it may have taken another component out. Any suggestions on what to test or replace?  I looked at IC9 (74HCT240N), and swapped it for a 74LS240N (didn't HCT on hand), and its still doing the same thing.

https://o.pinside.com/c/17/0d/c170de447bd8d412293f3b4b9a9627b9a14ac741.pdf

https://o.pinside.com/6/66/fe/666fe21714cdd0b15b94b2c99ec24a8a44a73617.pdf

#2 5 months ago

Do the activation switches have a capacitor and resistor wired on them? Might be a shorted capacitor if so. Try snipping one leg of the cap where it attaches to the switch and see if the problem persists. (Provided this game uses them--i think it does)

#3 5 months ago
Quoted from robm:

Have a Firepower that has the right slingshot locking on. It has a rottendog MPU/driver combo board installed that has been working fine for months.  I had to replace a fuse after the first time.
So coil resistance and diode tested OK, so i pulled the board out and replaced the drive transitor (q10) with an IRL540N.
Still the same - coil was locking on.
So then replaced the coil with a new one and new diode, and its still locking on.
However its a little strange in that the coil doesn't lock on at power up, only after the ball shoots into the shooter lane after a game is started. It also locks on when i go into the coil test.  I've also tested the slingshot switches with a multimeter and they test fine (ie: switch isn't closed).  I also have tried starting a game (it takes a couple of seconds to kick the ball out), and pulling the switch input switches (2J2, 2J3) from the board and the sling still locks on.
So it seems to me that maybe when the fuse blew the first time, it may have taken another component out. Any suggestions on what to test or replace?  I looked at IC9 (74HCT240N), and swapped it for a 74LS240N (didn't HCT on hand), and its still doing the same thing.
https://o.pinside.com/c/17/0d/c170de447bd8d412293f3b4b9a9627b9a14ac741.pdf
https://o.pinside.com/6/66/fe/666fe21714cdd0b15b94b2c99ec24a8a44a73617.pdf

Isolate the input switches for the sling:
Disconnect connector 2 J13 on the driverboard start game again to check sling coil still or does not energize.
sys6repairdriverconnectors (resized).jpg

#4 5 months ago
Quoted from frunch:

Do the activation switches have a capacitor and resistor wired on them? Might be a shorted capacitor if so. Try snipping one leg of the cap where it attaches to the switch and see if the problem persists. (Provided this game uses them--i think it does)

Snipped the cap - problem is still there

#5 5 months ago
Quoted from PINTEC:

Isolate the input switches for the sling:
Disconnect connector 2 J13 on the driverboard start game again to check sling coil still or does not energize.
[quoted image]

Removed 2J13, and coil still locks on - although if i remove 2J12, it doesn't lock on

#6 5 months ago
Quoted from robm:

Removed 2J13, and coil still locks on - although if i remove 2J12, it doesn't lock on

That points to a problem on the board (not the switches).

When you go into solenoid test the coil will lock on. When you exit coil test, does the coil disengage?

If so, I'd replace IC7 74HCT08 AND gate since you already replaced IC9

#7 5 months ago
Quoted from Schwaggs:

That points to a problem on the board (not the switches).
If you go into solenoid test the coil will lock on. When you exit coil test, does the coil disengage?

No, coil stays locked on when i exit coil test and go into switch test.

#8 5 months ago
Quoted from robm:

No, coil stays locked on when i exit coil test and go into switch test.

Try exiting diagnostics completely.

#9 5 months ago
Quoted from Schwaggs:

Try exiting diagnostics completely.

Replaced IC8, no change. I'm not sure how to exit diangostics without going through the whole thing, and don't want to cook the coil?

#10 5 months ago

Misread above - i also replaced IC7, still locking on

#11 5 months ago

connector 2J13 is the special solenoid switch inputs, 2J12 is the special solenoid drives.

the pre driver Q9 (2N4401) may be faulty?

can you check pins 4,5 & 6 on the 7402 IC9?
both inputs, pins 4 & 5, must be low for the output pin 6 to be high.
if both of the inputs are low the problem may be IC6 seeing as you have changed IC's 7,8 &9.

#12 5 months ago
Quoted from Rikoshay:

connector 2J13 is the special solenoid switch inputs, 2J12 is the special solenoid drives.
the pre driver Q9 (2N4401) may be faulty?
can you check pins 4,5 & 6 on the 7402 IC9?
both inputs, pins 4 & 5, must be low for the output pin 6 to be high.
if both of the inputs are low the problem may be IC6 seeing as you have changed IC's 7,8 &9.

On IC9, 4 is high, 5 and 6 are low.

This rottendog MPU does not seem to have predrivers, just the mosfets.

#13 5 months ago

Ic6 looks to be a bit of some sort of manufactured chip20210815_150845 (resized).jpg

#14 5 months ago
Quoted from robm:

No, coil stays locked on when i exit coil test and go into switch test.

Try exiting diagnostics completely.

You are trying to simulate "Game in progress" and "Game Over". Coils are enabled when you start a game (or enter diags) and disabled when you end the game (or exit diags). If the act of enabling and disabling the coils energizes and de-energizes the locked sling coil, that tells us something.

Trying to figure out where in the chain the signal is getting locked on.

Do you have a logic probe?

#15 5 months ago
Quoted from Rikoshay:

connector 2J13 is the special solenoid switch inputs, 2J12 is the special solenoid drives.
the pre driver Q9 (2N4401) may be faulty?
can you check pins 4,5 & 6 on the 7402 IC9?
both inputs, pins 4 & 5, must be low for the output pin 6 to be high.
if both of the inputs are low the problem may be IC6 seeing as you have changed IC's 7,8 &9.

This is a rottendog board - the chip numbers and circuit is different than an original Williams board that you are referencing.

#16 5 months ago
Quoted from robm:

Ic6 looks to be a bit of some sort of manufactured chip[quoted image]

Looks like they made their own through hole 74HCT154 from the available SMD chips. This chip hasn't been made in through hole form-factor for quite some time.

#17 5 months ago
Quoted from Schwaggs:

Looks like they made their own through hole 74HCT154 from the available SMD chips. This chip hasn't been made in through hole form-factor for quite some time.

Their system 80 board has these as well. Great Plains electronics had some of the DIP versions a couple months ago as I picked up a few to fix said RD SYS80 board.

#18 5 months ago
Quoted from slochar:

Their system 80 board has these as well. Great Plains electronics had some of the DIP versions a couple months ago as I picked up a few to fix said RD SYS80 board.

I wish I would have seen that! I could use some.

#19 5 months ago
Quoted from Schwaggs:

Try exiting diagnostics completely.
You are trying to simulate "Game in progress" and "Game Over". Coils are enabled when you start a game (or enter diags) and disabled when you end the game (or exit diags). If the act of enabling and disabling the coils energizes and de-energizes the locked sling coil, that tells us something.
Trying to figure out where in the chain the signal is getting locked on.
Do you have a logic probe?

OK, played a game by pulling 2J12 and checking through the game. Coil locks on when i momentarily put 2J12 back on as well as scores increase by 10 or 20 points each time.

When the ball drained at the end of the game, coil returned to normal (ie: not locked on).

yes, i have a logic probe, don't fully understand it but willing to learn and happy to share whether pins on ICs are high or low if you can give direction on which pins to test

#20 5 months ago

yeh my bad, was looking at an original schematic, not taking into account a different driver board.

so when you tested the pins, I assume the coil wasn't locked on?

also forgetting that you would need to desolder a wire from the sling coil when doing the test, need to test the NOR gate when the coil is on.
if the coil was on and you got those same readings it looks like IC6 to me.

your results show off, but it does look like you can use your logic probe.

to completely isolate the switches you could remove a wire?
the coil energising and subsequent scoring is the other switch that closes when the 'arm' moves.
there are the 2 switches through the playfield that energise the coil and one that closes which is part of the switch matrix that causes the scoring.

i'm wondering what you can put in place of the solenoid so as to do testing and not cook it......maybe 2 x 24V car/globes in series, this way when it's on you will see the globes light up?

#21 5 months ago
Quoted from robm:

OK, played a game by pulling 2J12 and checking through the game. Coil locks on when i momentarily put 2J12 back on as well as scores increase by 10 or 20 points each time.
When the ball drained at the end of the game, coil returned to normal (ie: not locked on).
yes, i have a logic probe, don't fully understand it but willing to learn and happy to share whether pins on ICs are high or low if you can give direction on which pins to test

Scoring is to be expected, there is a separate switch on slings and pops that is in the switch matrix that triggers sound and scoring. When you plugged in the coil and it fired, it triggered the switch matrix switch which added score.

So from the results of this test, we know that IC9 is enabling and disabling the coil properly. Everything downstream to the coil from IC9 is working properly. IC9 *could* still be at fault but we know everything else from there down is good.

Test 1) Swap IC7 and IC8 and see if the problem moves

Test 2) setup your logic probe
Remove J13
Probe the inputs to IC9 - they all should be HI (when in attract). Pins 6, 8, 11, 13, 15, 17

If one of these is LOW - trace back to the inputs to IC7 and IC8. Each of the inputs should be HI in attract. IC7 Pins 9, 10, 12, 13 and IC8 Pins 1, 2, 4, 5, 9, 10, 12, 13

If one of these is LOW, you either have a problem with a shorted capacitor or a bad PIA depending on which Pin is stuck low.

#22 5 months ago
Quoted from Schwaggs:

Scoring is to be expected, there is a separate switch on slings and pops that is in the switch matrix that triggers sound and scoring. When you plugged in the coil and it fired, it triggered the switch matrix switch which added score.
So from the results of this test, we know that IC9 is enabling and disabling the coil properly. Everything downstream to the coil from IC9 is working properly. IC9 *could* still be at fault but we know everything else from there down is good.
Test 1) Swap IC7 and IC8 and see if the problem moves
Test 2) setup your logic probe
Remove J13
Probe the inputs to IC9 - they all should be HI (when in attract). Pins 6, 8, 11, 13, 15, 17
If one of these is LOW - trace back to the inputs to IC7 and IC8. Each of the inputs should be HI in attract. IC7 Pins 9, 10, 12, 13 and IC8 Pins 1, 2, 4, 5, 9, 10, 12, 13
If one of these is LOW, you either have a problem with a shorted capacitor or a bad PIA depending on which Pin is stuck low.

Awesome.

1 - swapped IC7 and 8 - no change right sling still locking
2 - IC9 pins 6 and 8 are low in attract wiht J13 removed, 11,13,15,17 are high
3 - IC8 - tested all as high (good)
IC7 - pin 13 tested low when you suggested it should be high - all others were high as expected

#23 5 months ago
Quoted from robm:

Awesome.
1 - swapped IC7 and 8 - no change right sling still locking
2 - IC9 pins 6 and 8 are low in attract wiht J13 removed, 11,13,15,17 are high
3 - IC8 - tested all as high (good)
IC7 - pin 13 tested low when you suggested it should be high - all others were high as expected

Great job, you found the problem! IC7 Pin 13 should be HI - That is ST5 which is driven by IC26 6821 PIA. Do you happen to have another PIA laying around you can try?

If not, you can try swapping IC26 with IC27 or IC10.... when you do, the locked on solenoid should move to the other sling or one of the pop bumpers (following the bad pia to its new location). This will confirm the PIA is bad.

#24 5 months ago

Massive thanks to Schwaggs, i had a couple of 6821 spares on hand, swapped IC26 out and it works fine!

Really appreciate your assistance - i did notice that IC7 pin 13 led to ST5, but couldn't find where that was on the schematic, although can see it now you've pointed it out.

I would really like to understand how to understand what IC pins should be high and low, so i can do more of thhis sort of board work

Thanks again

rob

#25 5 months ago
Quoted from robm:

Massive thanks to Schwaggs, i had a couple of 6821 spares on hand, swapped IC26 out and it works fine!
Really appreciate your assistance - i did notice that IC7 pin 13 led to ST5, but couldn't find where that was on the schematic, although can see it now you've pointed it out.
I would really like to understand how to understand what IC pins should be high and low, so i can do more of thhis sort of board work
Thanks again
rob

You did all the heavy lifting, I was happy to help! Congrats on getting it back up and running!

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