Phantom pop bumper activations on Centaur

[David_Vi]

I'm getting very frustrated with this issue, I don't know what else to try.

During gameplay the left pop bumper (sometimes the right but it's rare) randomly fires when you're flipping. I can press the flipper button lots and at some point the left jet will fire.

I've checked the switch, even taped it so it can't make contact.
I can prop up the playfield, start a game (by pressing trough switches so it thinks there's balls), then flip with either flipper and the pop bumper will occasionally fire.
With it taped it still fires but doesn't score, which is also odd as surely with the switch able to make contact it shouldn't vibrate shut by the pop activating?

Here's an example

I've tried a new capacitor on the switch, as well as cutting it off, new diode.
Disconnecting the lane change switches on the flipper buttons.
Added caps to the flipper buttons (like on Williams games)
Redid the switch column connector on the board as it looked like this (coincidentally the knackered wire is the same column as the left jet (thumper bumper)


When it happens and if it scores it only scores 1000, so I'm not sure if it could be another switch, or I'd get points from that too?

Here's a copy of the switch matrix, although I'm not sure if it's really switch related.


The game has a brand new repro Nvram mpu, sdb and sound boards. The only original boards are the lamp boards and power rectifier.

At my wit's end

 

[new forest pinball]

If you have carried out the above thoroughly, then I would be repinning A3- J5 and A4 J2 and closely inspecting A4-J4 PIN number 5 before wasting any more time with switch taping shinanagins ……. Keef…….
(FYI on any bally/stern classic ss games that have been stood any length of time we always as a minimum for reliability re-pin A3 J3 and J4. And A4 J2 and J3 ) highly recommend you do this.

 

[David_Vi]

If you have carried out the above thoroughly, then I would be repinning A3- J5 and A4 J2 and closely inspecting A4-J4 PIN number 5 before wasting any more time with switch taping shinanagins ……. Keef…….
(FYI on any bally/stern classic ss games that have been stood any length of time we always as a minimum for reliability re-pin A3 J3 and J4. And A4 J2 and J3 ) highly recommend you do this.

Any hints of where to find 2.54mm connectors that go upto 25pins? Usually I use eBay for bits like this but it's failing me today.

I've googled the issue a bit and read stories of people separating their entire wire harness to stop interference between the switch and coil harnesses, I really hope my issue can be solved by other means because that is not for me.

Another example. Just hitting the flipper button with flipper held up (don't wanna wear out my new mechs!)

Is there any reason this cable is routed like this as it seems to go in the direction it came from.

 

[kevlar]

I have exactly the same problem on my Flight 2000 and Xenon Dave. On F2k the upper left sling fires randomly when flipping and sometimes although not very often, one of the pops does too. On Xenon one of the pops fires occasionally. Like you I've tried everything to stop it including disconnecting the switches altogether. I posted in the Flight2000 thread on pinside and got this reply..

" This happens occasionally on all bally/stern games of this era. The wiring in the game acts as an antenna and the switch matrix misinterprets a quick-react signal from that switch and fires the solenoid. Notice that you do not get any points for it. This is because the normal switch routine that handles the scoring correctly cancels out the quick react signal (that doesn't stay activated, to do the score routine).

They did this to make the slings and pops more sensitive (the capacitor that is sometimes there helps lengthen the pulse from the switch to ensure that they score, but they don't do much if anything for the solenoid activation portion of the software).

This behavior is called out in the Bally theory of operation; they didn't consider it worth fixing way back when. No one has come up with a definitive way to fix it today. I should try and modify the software to see if that helps but most of my games, for some reason, do not have this issue, so I wouldn't be able to tell if it made a difference. I should be able to tell if the slings and pops were less sensitive though.... let me think on how to change the software. Can you test it if I end up with something that works ok? You'd need some 2732/2716 eproms depending on how your mpu200 is jumpered and an eprom burner."

A few other people chimed in and said theirs was exactly the same.

The guy ( Slochar ) makes a modified rom for F2k, and after me bringing up the subject he set about seeing if he could stop it in software, which he did ( Paul burnt a rom for me ) and it did stop it completely. I eventually went back to the original rom though because his fix introduced another problem. As you said in your second post you could separate the wiring harness to potentially stop it happening but that seems like a lot of hassle. I've just learned to live with it.

 

[kevlar]

See the last paragraph on page 8 of the Bally Theory of Operation attached below for explanation..

 

[David_Vi]

Redid one connector and tried to rearrange the wire harness in the backbox. Did nothing of course but I suppose it's tidier!

I have exactly the same problem on my Flight 2000 and Xenon Dave. On F2k the upper left sling fires randomly when flipping and sometimes although not very often, one of the pops does too. On Xenon one of the pops fires occasionally. Like you I've tried everything to stop it including disconnecting the switches altogether. I posted in the Flight2000 thread on pinside and got this reply..

" This happens occasionally on all bally/stern games of this era. The wiring in the game acts as an antenna and the switch matrix misinterprets a quick-react signal from that switch and fires the solenoid. Notice that you do not get any points for it. This is because the normal switch routine that handles the scoring correctly cancels out the quick react signal (that doesn't stay activated, to do the score routine).

They did this to make the slings and pops more sensitive (the capacitor that is sometimes there helps lengthen the pulse from the switch to ensure that they score, but they don't do much if anything for the solenoid activation portion of the software).

This behavior is called out in the Bally theory of operation; they didn't consider it worth fixing way back when. No one has come up with a definitive way to fix it today. I should try and modify the software to see if that helps but most of my games, for some reason, do not have this issue, so I wouldn't be able to tell if it made a difference. I should be able to tell if the slings and pops were less sensitive though.... let me think on how to change the software. Can you test it if I end up with something that works ok? You'd need some 2732/2716 eproms depending on how your mpu200 is jumpered and an eprom burner."

A few other people chimed in and said theirs was exactly the same.

The guy ( Slochar ) makes a modified rom for F2k, and after me bringing up the subject he set about seeing if he could stop it in software, which he did ( Paul burnt a rom for me ) and it did stop it completely. I eventually went back to the original rom though because his fix introduced another problem. As you said in your second post you could separate the wiring harness to potentially stop it happening but that seems like a lot of hassle. I've just learned to live with it.

I may have stumbled upon your post in my Google session last night. I went down the rabbit hole and it wasn't all that positive once I'd realised I'd tried everything that worked for everyone else, meaning in probably in that category of having a game where the wiring just so happens to do this.

Afterall there are 1000s of games of this era, of the same title that don't have any issues.

What you're saying does explain something else I tried. I had assumed it was nothing to do with the switch matrix as I had blocked the pop switches from working. But in one test I unplugged the switches from the MPU and tried to replicate the issue. Maybe I didn't try it for long enough but I didn't get a pop activation once.

So it is (most likely) going by the test and what you were told, related to switches in a roundabout way. Originally I had thought it was the solenoids interfering with each other.

When I first noticed the issue it wasn't scoring points but since changing capacitors it does. If I had a time machine I'd go back to when it wasn't scoring as I could tolerate that in hindsight.
(I took the caps off and still it scores).

See the last paragraph on page 8 of the Bally Theory of Operation attached below for explanation..

Some good reading for me as I wasn't born when Bally service school was enrolling

 

[Moonraker]

Sounds like you need a ferrite core on the switch matrix loom for EMI suppression. Not sure how large the loom is so first link might be most appropriate. The second link has a smaller internal diameter but might be more cost effective with 3 or 4 wires per ferrite.

0444177081 | Fair-Rite Ferrite Sleeve | RS

uk.rs-online.com

0446164181 | Fair-Rite Ferrite Core | RS

uk.rs-online.com

 

[David_Vi]

Sounds like you need a ferrite core on the switch matrix loom for EMI suppression. Not sure how large the loom is so first link might be most appropriate. The second link has a smaller internal diameter but might be more cost effective with 3 or 4 wires per ferrite.

0444177081 | Fair-Rite Ferrite Sleeve | RS

uk.rs-online.com

0446164181 | Fair-Rite Ferrite Core | RS

uk.rs-online.com

Interesting, I read about people using these to mixed success. How do they work? I thought you'd have to insulate the entire loom.

 

[drhex]

EMI voltage spikes on the cable get dampened by the core as they induce a current in it. EMI doesn‘t have a lot of energy so this is pretty effective.

 

[DRD]

I get occasional phantom pops on my Paragon. It is the same for all players so I have not gone to exhaustive lengths to sort it.

Thanks @Moonraker for the Intel. My scared Stiff has 3 or more ferrite cores in the backbox and I wondered why. I think my former shadow might have had one up there too

I will treat Paragon to a few to see if 'owt changes.

 

[David_Vi]

I fiddled with it all day yesterday, by the evening I was fed up and thought I'd put the pop switches back to normal and have a rest from it but then just started changing LEDs

Usually I dislike cool white but I swapped a few into the backbox and thought they worked so changed all except the orbs and I think it works really well!
(I'd missed two others when I took this pic so ignore those)


When Claire got home we played a few games.
Then I noticed, the noise when the pop phantom fires is not the usual pop SFX.
So left it for the night and today it only took a couple minutes to realise the pop firing was setting off the star rollover next it and sometimes one of the 1000pts standup targets behind the ORBS drops.

So it wasn't scoring! I didn't need that time machine. I am now happy to tolerate the phantom pop for a while as it doesn't score.

I'll look into ferrite cores soon, I'm just happy to have it in a fair playable state so I can get away from it for a bit

 

[*paulb*]

Had an email exchange with someone several years ago that had a similar problem (phantom pop bumpers) on a Fathom. We never did get to the bottom of it - tried everything as described in this thread - except for ferrites. Thinking now it might have been EMI.

I wonder if a faulty or partially failing solenoid flyback diode could be an EMI source?

 

[kevlar]

Damn EMI!

 

[AlanJ]

I have tied switch matrix rows to ground using 10-20k resistors to eradicate rogue triggers. Yes I know they are tied low using resistors on the MPU, but it helps to tie them down at the source of the issues - i.e. under the playfied, where noise is more likely to occur.

 

[David_Vi]

I have tied switch matrix rows to ground using 10-20k resistors to eradicate rogue triggers. Yes I know they are tied low using resistors on the MPU, but it helps to tie them down at the source of the issues - i.e. under the playfied, where noise is more likely to occur.

I'll try that when I've got the resistors. For now I have a task list for Claire's Creech

 

[HomerRamone]

I'll look into ferrite cores soon, I'm just happy to have it in a fair playable state so I can get away from it for a bit

This is a trap - and the reason I've not started doing mine.. Ill just wait a while and play a bit more

 

[Moonraker]

Interesting, I read about people using these to mixed success. How do they work? I thought you'd have to insulate the entire loom.

You can actually insulate the entire loom, it's called shielding (or screened). The problem is it's a lot more expensive and adds weight, thanks to all the extra shielding wire. If you know the cause then it may be possible to just shield that particular wire or wires but that can take a lot of time and effort to identify.

Thanks @Moonraker for the Intel. My scared Stiff has 3 or more ferrite cores in the backbox and I wondered why. I think my former shadow might have had one up there too

Yes, they're quite common on some latter games, as knowledge of how to stop interference improved.

Also depends on what the cause is - I suspect it may be the flipper coil being activated but it's tied in with a particular transmission line which is acting as an antenna. Then another line may be acting as a receiver feeding the pop bumper (or MPU!), causing it to be activated. In the B/W WPC era, it may be the DMD that is the cause, which is right next to the cables that the ferrites are on.

I wonder if a faulty or partially failing solenoid flyback diode could be an EMI source?

Could be, or it could be something else. That is one of the problems with EMI, it can be hard to determine the cause without the right (can be very expensive) detection equipment.

I have tied switch matrix rows to ground using 10-20k resistors to eradicate rogue triggers. Yes I know they are tied low using resistors on the MPU, but it helps to tie them down at the source of the issues - i.e. under the playfield, where noise is more likely to occur.

Again another solution, this time to stop floating signals. Probably a very good solution in the case of pop bumpers being triggered but again it depends on the source (or cause) and how it's happening and how sensitive the trigger signal needs to be for something to be activated. It could be that the original design had the resistors in but were removed as a cost saving versus the odd pop bumper activation that many people won't notice when playing on site. Or it's being caused by aging electronics that were not design to last for so long, so no need for them originally.