WAS SOLVED NOW BACK AGAIN!: Kicker switch issue Gorgar

[Andy B]

Been helping someone out with a Gorgar that would not start a game.

Got it working so whilst I was there tested all the switches and coils.

Left kicker switch not registering in switch tests. Switch has a capacitor (22 mfd 100 volt electrolytic capacitor according to pinball repair manuals) that has broken off. This is the first time I have come across a capacitor on a kicker switch. What role does the capacitor play on this type of switch please? Reading the system 6 repair manual it says the kicker is a special solenoid which is not cpu controlled so from my limited knowledge of electronics I am guessing the capacitor stores an electrical charge and when the switch closes the charge is discharged to "manually" trigger the kicker?

I can swap it out for one of a higher voltage rating right so long as the uf rating (22) is the same? e.g.:

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Thanks

Andy

 

[stevebm1]

yes uping the voltage rating is fine as long as the uf value is the same

 

[Andy B]

yes uping the voltage rating is fine as long as the uf value is the same

Thanks. I managed to get an exact match from Cricklewood Electronics on EBay.

 

[Jay Walker]

Hello, Andy,

Confusingly, 'Left Kicker' in switch tests isn't the switches touching the rubber band.

Williams threw us a googly or curve ball with their 'Special Solenoids'. The idea was to have an optimum response for bumpers and slingshots, achieved by not having the cpu detect the switch, and then pulse the coil. Instead, the switches that poke through the playfield to be operated by the ball/rubber band simply switch the coil transistor, using some logic gates on the driver board. The first that the cpu and program knows about this is when a 'scoring' switch below the playfield, operated by the slingshot linkage, closes. So if the slingshot does operate, but doesn't score any points, produce a sound effect, etc, the scoring switch is at fault. If it doesn't operate at all, the scoring switch could be okay, with the problem in the 'special' switch/gating/solenoid drive section.

The capacitor and resistor used on the special switches improves the sensitivity of the switch(es), so that it isn't necessary to have an unwisely small gap on the contacts* - the problem with this set-up is that contacts staying closed holds the transistor and coil On, with damaging consequences.

* though a slingshot would tend to repeatedly 'chatter' if its switches were too close

I've made many attempts to explain this area, starting with Gorgar, actually. Though I couldn't get it across to 'Wes'.

 

[Andy B]

Hello, Andy,

'Left Kicker' in switch tests isn't the switches touching the rubber band.

Williams threw us a googly or curve ball with their 'Special Solenoids'. The idea was to have an optimum response for bumpers and slingshots, achieved by not having the cpu detect the switch, and then pulse the coil. Instead, the switches that poke through the playfield to be operated by the ball/rubber band simply switch the coil transistor, using some logic gates on the driver board. The first that the cpu and program knows about this is when a 'scoring' switch below the playfield, operated by the slingshot linkage, closes. So if the slingshot does operate, but doesn't score any points, produce a sound effect, etc, the scoring switch is at fault. If it doesn't operate at all, the scoring switch could be okay, with the problem in the 'special' switch/gating/solenoid drive section.

The capacitor and resistor used on the special switches improves the sensitivity of the switch(es), so that it isn't necessary to have an unwisely small gap on the contacts - the problem with this set-up is that contacts staying closed holds the transistor and coil On, with damaging consequences.

Thanks. The kicker is not kicking. I saw the scoring switches under the playfield beneath each kicker.

I tested the right kicker in switch diagnostics and the kicker worked and a switch registered but, from your description, I’m guessing that was the scoring switch and when I tested the left kicker there was no switch registering as the kicker was not kicking and thereby triggering the scoring switch. Hopefully swapping out the broken capacitor will solve the issue and I don’t have to mess about with the solenoid drive section…

 

[Jay Walker]

Andy B wrote; "I’m guessing that was the scoring switch and when I tested the left kicker there was no switch registering as the kicker was not kicking and thereby triggering the scoring switch"

That's right, in the brief overlap of Special Switches and Test Report, a non-functioning bumper or slingshot would produce "Check Switch, Jet Bumper/SlingShot" due to the scoring switch being unseen.

The 'special' switches connect their input to ground, pulling a chip (and gate) input Low. The gate requires two Low inputs to produce a High output (the other is already Low while a game is in progress) and this results in the pre-drive transistor being switched On, in turn switching the larger drive transistor.

 

[AlanJ]

It’s most likely an issue not related to the capacitor but more likely the driver board not responding to the switch closure - special solenoid circuit needs looking at. the logic chips often fail

 

[Andy B]

It’s most likely an issue not related to the capacitor but more likely the driver board not responding to the switch closure - special solenoid circuit needs looking at. the logic chips often fail

Oh dear...

 

[AlanJ]

Oh dear...

The TIP120/TIP102 that drives the solenoid is driven by a 2n4401 transistor, which is driven by a 7402 ic, driven by a 7408 ic - Those 2 ics are prone to getting blown up - i'd check with a logic probe to see if each is working properly. and then finally the transistor.

 

[Andy B]

The TIP120/TIP102 that drives the solenoid is driven by a 2n4401 transistor, which is driven by a 7402 ic, driven by a 7408 ic - Those 2 ics are prone to getting blown up - i'd check with a logic probe to see if each is working properly. and then finally the transistor.

Cheers Alan. Will be going back next week so will update then.

 

[Jay Walker]

Try verifying the coil and its return wiring, though, i.e. temporarily (just momentarily) ground the metal tab of the power transistor. The coil will operate if it and the return circuit are alright.

As a guide, the first component in from the special switch is an 'And' gate, in a 7408 chip. The switch connecting to ground pulls an input of this gate Low, so its output follows and goes Low. The other input to the And gate is used by the program to pulse the coil, usually only during the Solenoid test. Either of them going Low produces a Low output.

This line then becomes one input to a 'Nor' gate, in a 7402 chip. Two Low inputs to this gate are required to produce a High output, switching the 4401 pre-driver transistor. The other input here, often known as the 'Game On' line, is shared by the Nor gates of all six Special Solenoid drives, and also switches the flipper relay*. It drops Low when a game is started, or upon going into bookkeeping/diagnostics.

* after a spare gate is used as an Inverter, to bring it High again

 

[Andy B]

Replaced capacitor and manually fired the kicker by grounding the transistor.

Fired fine so issue is with the ICs as suggested I guess.

Have brought driver board home to replace and socket the chips.

 

[Andy B]

I can't read the Logic Diagram for the driver board!

There are 2 x 7402N and 2 x 7408N ICs in that section. One of the 7402Ns has been socketed so I'm guessing previous owner had problems with that one in the past (but as far as I can tell from visible inspection of upper side of board tracks - see below - this one is not connected to my faulty left kicker).

I was thinking I might just replace and socket all 4 ICs in that section but I don't really want to mess with chips that don't have issues.

For the life of me I can't work out from the logic diagram which chips control the left kicker solenoid.

However, if I follow track on the upper side of the board from the pre-driver concerned (Q8 is the driver transistor) (all pre-driver and driver transistors test OK with board out of machine) they go to the bottom one of the two horizontally mounted 7402N in that section and then follow the tracks from that 7402N they go to the bottom one of the 2 horizontally mounted 7408Ns in that section - is that a safe way of working it out?

P.S. When taking these photos I noticed a transistor appeared to be missing at Q12 but checking the manual this transistor and associated solenoid are marked as "Not Used" though there is a pre-driver for it. Can anyone explain the logic to that to me please?

PPS I didn’t test with logic probe as I haven’t taught myself how to use one yet!

Thanks

Andy

 

[Jay Walker]

The drive transistor is Q8?. Take whatever Special Solenoid number it is, 4?, and the switching side, the Special Switch Trigger SST will also be number 4. So the And gate will be the one with ST4 heading for it, and the switching circuit lies to the left of your finger in the picture.

 

[Andy B]

The drive transistor is Q8?. Take whatever Special Solenoid number it is, 4?, and the switching side, the Special Switch Trigger SST will also be number 4. So the And gate will be the one with ST4 heading for it, and the switching circuit lies to the left of your finger in the picture.

Thanks. I got it now. Drive transistor = Q8, Pre driver = Q7. ST = 4. 7402N = IC 8. 7408N = IC6. Now where's that soldering iron and solder sucker...

 

[Jay Walker]

There is something you could've tried, since Special No.6 isn't used. As someone asked a while ago, it's feasible to move the coil drive wire and the Special Switch wire to an unused circuit. It depends how you feel about such a modification, or bodge as it could be regarded, and if circuit 6 is working itself. The cpu would only be affected when it came to solenoid test, the coil would pulse as No. 22 rather than No.19 20. But I read now that the drive transistor's missing. Probably 'borrowed' as a replacement. The label looks like it's numbered '26097', which would mean it was originally fitted in a Firepower, Williams number 497. In that case, it would've driven a slingshot, the right side I think.

To speak of always learning, I've only realised just now that the later revision of Williams' driver board doesn't have pre-drivers for solenoids - Specials 1 to 6 have drive transistors 1 to 6.

 

[Andy B]

Replaced and socketed IC6 and IC8. Problem solved. Cheers for all the advice!

 

[Andy B]

Was called back to look at Gorgar again.

This time left bumper coil had locked on (they switched it off when they saw smoke coming from under playfield).

I tried the usual:

Checked coil resistance - All good and plunger moves freely in sleeve so looks like no permanent damage done there
Checked coil trigger switch - not trapped closed
Replaced coil trigger switch diode - Coil still locking on
Replaced coil trigger switch capacitor - Coil still locking
Removed driver board
Tested coil transistor and pre-driver - Both tested good in board but swapped them out anyways just in case - coil was locking on

So I replaced the 7402N at IC 8 that I had replaced a few weeks back (which had resolved the issue with the non working left kicker).

Replacing that IC8 solved the locking on left bumper (after I had to trace a loose connection issue that meant no power was getting to any of the coils!) but now the left kicker won't work again :-(

It surely can't be a coincidence that these are both special solenoids and both connected to IC8 but the guy had played the game for a few weeks with no issues before the left pop bumper coil locked on so i don't think swapping out IC8 (which resolved the left kicker issue) caused the left bumper issue - that would have happened straight away wouldn't it? Also don't know why swapping out IC8 again has fixed the locking on left bumper coil but now left kicker is not working again. Am I missing something simple here?

Thanks

Andy

 

[Jay Walker]

Does the left slingshot work in the solenoid test? For the cpu to switch Special Solenoid 4, it brings 'ST 4' low, at one of the AND gates in IC 6. This gate switches Low (and can switch the NOR gate of IC 8) either when the playfield switch closes, or when the ST line goes Low. The NOR gate switches its output High, and should operate the solenoid when both its inputs are Low. One of these is the Enable/Disable line common to all the Special Solenoid circuits, the other comes from the circuits' own AND gate.

In an attempt to summarise;

1. Playfield switch OR Solenoid ST line going Low switches AND gate to a Low output
2. IF Enable/Disable is Low (Game in progress, or in diagnostics), Point 1 switches NOR gate to a High output, operating pre-driver, etc
3. But IF Enable/Disable is High (Game Over, or tilted), Point 1 has no effect on the Low output of the NOR gate, and driver circuit remains Off

 

[Moonraker]

Am I missing something simple here?

Quite possibly... connectors and in this case I would suspect the interconnect. It can be replaced (https://www.pinwiki.com/wiki/index.php/Williams_System_3_-_7#The_.22Once_Dreaded.22_40-pin_Connector) but for peace of mind I'd rip out the old board set and replace with new. As you've found it can save a lot of hassle and agro. I practice what I preach, here's the Gorgar I look after:

 

[Andy B]

Does the left slingshot work in the solenoid test? For the cpu to switch Special Solenoid 4, it brings 'ST 4' low, at one of the AND gates in IC 6. This gate switches Low (and can switch the NOR gate of IC 8) either when the playfield switch closes, or when the ST line goes Low. The NOR gate switches its output High, and should operate the solenoid when both its inputs are Low. One of these is the Enable/Disable line common to all the Special Solenoid circuits, the other comes from the circuits' own AND gate.

In an attempt to summarise;

1. Playfield switch OR Solenoid ST line going Low switches AND gate to a Low output
2. IF Enable/Disable is Low (Game in progress, or in diagnostics), NOR gate switches to a High output, operating pre-driver, etc
3. But IF Enable/Disable is High (Game Over, or tilted), no effect on the Low output of the NOR gate, and driver circuit remains Off

I walked away after getting the left bumper working without licking as I’d already been there a couple of hours resolving that (and the issue with lack of power to all coils as a result of a loose connector from backbox) so I didn’t get a chance to start diagnosing the issue but last time it went I replaced IC8 and that sorted it.

They were OK with the kicker not working - they were just so happy I got machine working again without left bumper coil locking on - so I said I would take a look at it next time I was there (I’m sure there’ll be something else that’ll crop up) - I could do with a break from the machine if I’m honest!

I will update post when I go back and have another go at it.

 

[Andy B]

Quite possibly... connectors and in this case I would suspect the interconnect. It can be replaced (https://www.pinwiki.com/wiki/index.php/Williams_System_3_-_7#The_.22Once_Dreaded.22_40-pin_Connector) but for peace of mind I'd rip out the old board set and replace with new. As you've found it can save a lot of hassle and agro. I practice what I preach, here's the Gorgar I look after:

View attachment 175624

Yep, I told them about the replacement board and that it would be £300 plus (though I don’t think Pinball Palace have them in stock currently).

They’re reluctant to shell out that much just to fix that one issue (though it would obviously be a big issue for us collectors/players), plus I think they only paid about £300 for the machine in the first place (a good few years back).

 

[s000m]

Yep, I told them about the replacement board and that it would be £300 plus (though I don’t think Pinball Palace have them in stock currently).

They’re reluctant to shell out that much just to fix that one issue (though it would obviously be a big issue for us collectors/players), plus I think they only paid about £300 for the machine in the first place (a good few years back).

Pretty bonkers if they could sell this for way more than £600.

Had the same with this JD I picked up.

18 broken switches in the report a garbled DMD and broken glass everywhere...

If they don't want to repair it. Offer to buy it off them?

 

[Andy B]

Pretty bonkers if they could sell this for way more than £600.

Had the same with this JD I picked up.

18 broken switches in the report a garbled DMD and broken glass everywhere...

If they don't want to repair it. Offer to buy it off them?

They’re not interested in selling it and it’s definitely not my bag.