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(Topic ID: 272008)

Ni-Wumpf isn't responsive to TILTING?


By JethroP

3 months ago



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  • Latest reply 3 months ago by KenLayton
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#51 3 months ago
Quoted from JethroP:

With this additional bit of information, can the experts following thread this come up with an inexpensive fix?

Buy a metal stern bob and try that?

#52 3 months ago

Sorry guys, I don't get on Pinside that much anymore. Definitely contact me at ace@ni-wumpf.com with questions like this. Jeff did yesterday, which is how I realized this thread was going on.

Tilt unresponsive: this is common, the switch is a graphite bob on one side of the contact, and a brass ring on the other. It is nothing like the gold-plated contact switches through-out the game, and is not going to last 40 years in operation as we expect it to. The transmissivity of the contact is just not there, so getting the contact to drive the strobe line to '0' volts is going to need some effort on our parts. I like the idea of the Stern metal plumbbob, but haven't tried it, and Marco is out of them. So last night, I took steel wool to the graphite bob, *and* the brass ring (and even the area where the metal rod contacts the tilt frame). On my Sinbad, it made a world of difference, though I'd say it still missed 1 out of 4 "hits". My bob is pretty "dinged" up along the graphite from hitting that ring, so I'm not too surprised.

There is likely nothing wrong on the board guys, and no chip/diode you can change to address this, unless you want to mess with every switch on the front door (these are the common return line switches). If your game start button is working than your chips are OK.

If someone *does* have a metal bob - I'd be interested in hearing the results.

-Ace

#53 3 months ago
Quoted from DoverPros:

the switch is a graphite bob on one side of the contact, and a brass ring on the other. It is nothing like the gold-plated contact switches through-out the game

As noted in post #16 of this thread, the pull-up resistor on the switch return line the tilt switch is on is 1k ohms (Gottlieb boards have a 2.7k ohm pull-up resistor). This doesn't help a resistive plumb-bobs cause.
Is there any reason a higher value pull-up resistor (say 10k ohms) couldn't be used to make it easier for the plumb bob to pull the signal to zero volts on fast activation?

#54 3 months ago
Quoted from slochar:

Whatever this ends up being, it's a design deficiency with the Pascal boards as well, because I don't have Niwumpf's in my 2 system 1 games - I forget which one has the issue most of the time I think it's countdown, the joker poker seems to be ok.
Now that I think of it, I think zacaj has an issue with his Genie, where it tilts and sometimes it doesn't, which I definitely experienced there, and he's got the LISY board in his! Maybe there's some subtlety with the original gottlieb boards that the aftermarket boards are missing when reading the tilt bob area?
I'm off for a couple days so maybe I'll stick the scope on it and see what's going on. Also I'm curious on the switch scanning speed - didn't see it listed in the service manual. I thought the processor on system 1 was much slower than others, but it's a completely different design so that might not matter in relation to switch scanning speed.
I think a purpose built circuit could be created to fix this.

To add to this, although I'm not sure if it's relevant here: my LISY board had issues with many standup switches too. No matter how close I gapped them and how much I cleaned them, they wouldn't register consistently. I've since repaired an original gottlieb MPU and installed it, no more issues with the standups, and the tilt seems more sensitive.

I'll see if I can measure the strobes on the original MPU and maybe the LISY too for comparison... I don't have direct access to any Ni Wumpf MPUs though

Update:

original MPU scans all columns at 60Hz. pasted_image (resized).png
It does a weird double pulse consistently, not sure why, but I guess that winds up as a 3ms pulse width? pasted_image (resized).png

#55 3 months ago

Remember Quench - this is an active LOW signal. A lower pull up value on the return is likely to help reactance - not the reverse. So no, a 10k pull-up would be going the wrong direction - especially if there is any resistance in the contact surfaces. It'll help the recovery signal, so that you can strobe faster, but that too is not the intent.

-Ace

#56 3 months ago
Quoted from DoverPros:

Remember Quench - this is an active LOW signal. A lower pull up value on the return is likely to help reactance - not the reverse. So no, a 10k pull-up would be going the wrong direction - especially if there is any resistance in the contact surfaces. It'll help the recovery signal, so that you can strobe faster, but that too is not the intent.
-Ace

Wait, but isn't a higher value pull up weaker? So if the bob is trying to pull the signal down (since it's active low), the weaker the pull down, the lower it will go, which should make it easier to sense? You said in your email that the problem was that it was having trouble driving the signal to 0 due to the bad connection of the bob-ring, not an issue with the pulse length?

#57 3 months ago
Quoted from DoverPros:

this is an active LOW signal. A lower pull up value on the return is likely to help reactance

Respectfully, I don't see your logic here.
If the plumb-bob is having trouble pulling the signal LOW because of resistive contact, then a *higher* value ("weaker" as Zacaj put it) pull-up resistor will allow the signal to swing low easier.

The question is whether there would be any side effects of raising the pull-up resistor value, i.e. will the R0 return signal accidentally trigger on noise interference through the cabinet/playfield wiring harness?

Out of curiosity, can you explain the Ni-Wumpf software logic to determine a "valid" tilt switch activation? i.e. how often are switches scanned, and how long do the switch return signals need to be active LOW to be considered a valid switch activation and not just noise/switch bounce? Or does your software switch matrix scan method work differently? (I come from the Bally world)

With the lower 1k ohm pull-up resistor being used, shouldn't the C7 "switch settling" capacitor be raised in value to hold an activated low signal longer?

#58 3 months ago

Gents, in a series circuit, where there are two resistors R1 (the pull-up), and R2 (the resistance of the contact at the plumb bob from bi-metal contact), the higher the pull up resistance (R1), the greater the voltage drop will be measured (whatever the current) across that part of the series network. So in the conductance case, you'd be right, with all that voltage across R1 (especially if we pull it higher), the lower the signal would drop as measured across the contact (R2). This would be good, as you guys describe.

But we are not seeing "contact", and the reason isn't the voltage, it is the *width* of the voltage pulse (zacaj' picture above is, after taking away the double pulsing, pretty generous. The normal pulse is 15 - 40 mSecs active-low depending on the board) . We are trying to increase *reactance*, not conductance - the inverse of capacitance across that contact. Which means we hope to pump current across those contacts to overcome whatever the RC value of that contact is (lower the pull-up resistor). I can't change the filtering capacitance on the input circuit on the board, or when you press the start button, you'd register more than one "game start" request occasionally. So I have to change the 'Q' response of the contact during a pulse (skip the rest of the parts of that equation that I cannot change, like chokes and crap) - to do that, I have to pump more current: i.e. lower the resistance of the pull-up, and hope that the resistance of the plumb-bob contact is still minimal when compared to a 1K pull-up. When you think about it, at what point would it make a difference if the pull up is 10K or 1K - probably right around 100 Ohms contact resistance value. I don't think that this is the case, so I doubt that we care about the resistance of the pull-up.

Having said all that - it's a crap shoot. At design time, you start somewhere, put a scope on the signal (with capture), set your scan frequency, and see what the return signal looks like as we tweak the return capacitance / resistance values, coupled with the strobe signal pull up resistance. Fun huh?

Now, to answer the question: on the original board, we did logic debouncing of a contact - in other words, a valid switch is identified after 3 active low pulses are received sequentially on the return line from the same strobe line at the 8279. That is not normal for a pinball CPU, but at the time, I was into acoustics, and a purist, this was how we did things to be absolutely sure that transient signal spikes from the rest of the game were not being seen on the return circuits showing false signals. In 1995 it worked great! Even for the plumb bob (or so I thought then with the game I had) It was partly this circuit design that allowed us to really improve spinner target response. We could detect spinner closure 2 - 3 times the amount that the original board could, and this was one of the odd goals we had (remember the reactance spiel). With the new board, we tried conditioning the return pulse with a more complex circuit (check the schematics between the 2 boards), and do away with switch debounce. Embarrassingly, that worked just as well, and the response seems about the same. It cost more, but the return circuits were pretty much bullet-proof - you could short a coil voltage to the returns, and not blink (though, that would probably take out the strobes).

Now, how fast are they strobed? I can look it up, but remember we are strobing the displays at 2X the speed of the switches. We need to fit 8 strobe lines into one full strobe "cycle". Whenever I change the active low pulse width, I also wind up changing the width of the full pulse cycle on the displays. I think the default width is 15 mSecs as I mentioned above - the original board used closer to 40 mSecs active low, which will definitely help improve switch detection of the plumb bob, but then you've lost your spinner response, (and overall playfield response feel).

Now, you can change this on the new board: set the options to EXPERT mode and tweak the switch strobe speed. It shouldn't affect the game - though it might make the displays a little less crisp. Don't go past 40mSecs. This will help the plumb bob response, by reading the signal, hopefully after the reactance curve falls to the acceptable level, and won't affect the front door switches.

In the end, everything is a trade-off. Electronically, you get fast game play, or a good plumb bob. If you want to run a System 1 tournament, clean the bob, and the brass contact ring, you won't be disappointed, if that is still not great, set the switch strobe speed higher, and put the game into Tournament mode. Sorry, this isn't an option on the older boards.

-Ace

#59 3 months ago

Thanks for the explanation Ace,
I have no experience with Gottlieb in this regard as I'm from the Bally world. They require active high switch returns which seems the better approach and gives more margin to sense active TTL switch signals, but that's another matter. They use 56k ohms pull-down resistors with no switch smoothing caps on the MPU board - these caps are fitted directly and only across fast react switches (tilt mech being one of them) with a value of 0.05uF - hence the O.P asking about installing caps on the Gottlieb tilt switch plumb-bob mech.
Bally scans the switch matrix every 8.3ms. Each strobe line is active approx 257us and the switch returns are read at the 238us mark. Two consecutive active high signal returns on a switch are then considered a "valid" closure. The switch has to be serviced then sensed as open before it can be validated a new time and this works very well. I don't know if you're handling debounce in software or via the 8279 keyboard mode.

With the tilt plumb-bob closing/opening instantaneously unlike the swiping action of all other game switches seems to me makes it difficult to sense sequential closures in this scanned matrix circuit. With that in mind, if someone was to design a circuit to sense the plumb-bob activation and have it simulate a longer hard switch closure, what's the optimal time of the active low pulse you want to see?

#60 3 months ago
Quoted from Quench:

, if someone was to design a circuit to sense the plumb-bob activation

Quench, if I’m reading into your question that you are up to the task, you da man!!!

#61 3 months ago

couldn't you just add a cap to the plumb bob to draw out the signal longer so the board can see it easier?

#62 3 months ago
Quoted from CaptainNeo:

couldn't you just add a cap to the plumb bob to draw out the signal longer so the board can see it easier?

No. Read this entire post. Been asked and answered already. Also, read this post: https://pinside.com/pinball/forum/topic/capacitors-on-switches-for-gottlieb

#63 3 months ago
Quoted from JethroP:

No. Read this entire post. Been asked and answered already. Also, read this post:

I don't think anyone in that thread actually said that a cap won't lengthen the pulse? I'm not seeing one offhand. It's not helping in your case, but is there really an electrical reason why the cap doesn't lengthen the pulse here? I don't know of one, and the fact that this isn't helping suggest it's not a 'length' issue to me...

I'd love to actually get a scope on your machine and see exactly how long the pulse is lasting, if a cap effects it, and how low the voltage is getting during that pulse...

Quoted from DoverPros:

The transmissivity of the contact is just not there, so getting the contact to drive the strobe line to '0' volts is going to need some effort on our parts

Quoted from DoverPros:

But we are not seeing "contact", and the reason isn't the voltage, it is the *width* of the voltage pulse

DoverPros seems to have said both ways, so I'm confused on that end. Is the issue that the pulse is too short, or the issue is that bad contact isn't pulling the voltage down enough?

#64 3 months ago
Quoted from JethroP:

Quench, if I’m reading into your question that you are up to the task, you da man!!!

Sorry not me, I don't have any system 1 games to test it on.

In the meantime, I still think the diode/cap has some merit, *but* a 1N4004/1N4148 diode isn't going to cut it and neither is a 0.047uf capacitor in this circuit.
The logic low level for a TTL chip is considered between 0 and 0.8 volts. The MPU board wants to see the active closed switch signal in that range for a period of time.

A low current voltage drop across a 1N4004/1N4148 diode is approx 0.72 volts leaving you next to no room and that's assuming the MPU board manages to pull the strobe line down to zero volts.
That's the reason I asked if you had a 1N5819 diode. The low current voltage drop across them is about 0.25 volts giving you more headroom before the signal upswing moves into the indeterminate logic level voltage.
The 1k ohm pull-up resistor on the MPU board will charge a 0.047uf capacitor too fast rendering it useless in this application. You might need something like a 10uF cap to hold the closed switch state longer.

But I'm only guessing - not sure I can add much more here since I don't have any games of this series to experiment with.

#65 3 months ago
Quoted from zacaj:

I'd love to actually get a scope on your machine and see exactly how long the pulse is lasting, if a cap effects it, and how low the voltage is getting during that pulse...

You are welcome to come, and even invited and encouraged!! You're in Rochester, I'm in San Jose. I found you a flight end of the month, round trip for $202. Don't forget to bring your scope. I don't have one.

#66 3 months ago
Quoted from Quench:

That's the reason I asked if you had a 1N5819 diode. The low current voltage drop across them is about 0.25 volts giving you more headroom.
The 1k ohm pull-up resistor on the MPU board will charge a 0.047uf capacitor too fast rendering it useless in this application. You might need something like a 10uF cap.

I'm happy to experiment. I'll have to buy a 1N5819 diode and a 10uF cap. If anyone has one they could drop in the mail I'd appreciate it, otherwise, I'll end ordering one. I think I have a cap.

#67 3 months ago
Quoted from Quench:

not sure I can add much more here since I don't have any games of this series to experiment with.

Does the diode and cap go across the bob/switch? And should the cap be a ceramic disc, or can it be electrolytic?

#68 3 months ago
Quoted from JethroP:

Does the diode and cap go across the bob/switch? And should the cap be a ceramic disc, or can it be electrolytic?

Disconnect the strobe wire from the tilt mech.
Banded side of the diode on the strobe wire.
Non-banded side of the diode to the tilt mech where the strobe wire was connected.
Capacitor across the two contact points of the mech.
If you're using an electrolytic capacitor, connect the negative lead to the non-banded side of the diode.
Identifying the strobe wire is the one that does NOT connect onwards to the coin switches and start button.

Hopefully this helps, if not something more fool proof needs to be done.

#69 3 months ago
Quoted from Quench:

Disconnect the strobe wire from the tilt mech.
Banded side of the diode on the strobe wire.
Non-banded side of the diode to the tilt mech where the strobe wire was connected.
Capacitor across the two contact points of the mech.
If you're using an electrolytic capacitor, connect the negative lead to the non-banded side of the diode.
Identifying the strobe wire is the one that does NOT connect onwards to the coin switches and start button.
Hopefully this helps, if not something more fool proof needs to be done.

Thanks. I am ordering parts and will report back, probably in a week or two.

#70 3 months ago

Update from arcade owner is that his all have pascal boards, and they all tilt. He will be setting up another game in a couple weeks and putting a NiWumpf in it to check out its response.

If the switches are active low as Ace says adding a cap will do nothing to lengthen a low pulse (it would make it shorter, if anything). Seems "backwards" to me, if the normal state of the switch is high, so the pulse is low. I wonder what the design philosophy behind that was?

#71 3 months ago
Quoted from slochar:

Update from arcade owner is that his all have pascal boards, and they all tilt.

Confirmed that my Joker Poker + Pascal tilts no problem.

#72 3 months ago
Quoted from slochar:

Update from arcade owner is that his all have pascal boards, and they all tilt. He will be setting up another game in a couple weeks and putting a NiWumpf in it to check out its response.
If the switches are active low as Ace says adding a cap will do nothing to lengthen a low pulse (it would make it shorter, if anything). Seems "backwards" to me, if the normal state of the switch is high, so the pulse is low. I wonder what the design philosophy behind that was?

Aren't most games active low? WPC at least, I think sys 3-7 too? On my homebrew I found it helps with avoiding stray switch activations from induced current from nearby solenoids

#73 3 months ago

The strobe being low is what I mean. Maybe most games are - I thought Bally sent a positive pulse (I guess any multiplexed PIA would have to?)
Is it easier to detect a low or a high pulse vs. noise?

#74 3 months ago
Quoted from stevevt:

Confirmed that my Joker Poker + Pascal tilts no problem.

I have joker poker with pascal as well. Also tilts no problem. As does my count down with pascal.

#75 3 months ago
Quoted from JethroP:

Thanks. I am ordering parts and will report back, probably in a week or two.

Quench, you are a hero! Your solution works!!
Installed 10uF ceramic cap and 1N5819 as you suggested. Works every time. Even took out the metal bob and reinstalled my old graphite bob and works perfectly. I'm sure others will find this solution to their problem. No doubt Ni-Wumpf will now recommend this in the future. They should pay you a royalty/consulting fee for solving their design problem.

Thank again!!!

#76 3 months ago

Great to hear! thanks for the update

#77 3 months ago

see the cap method did work. With an altered addition.

#78 3 months ago

Glad this helped get the tilt working properly.

The instructions should be included with each Ni-Wumpf system 1 cpu board.

#79 3 months ago

Great job guys!!! I sold my Sinbad to a good friend. I'll put together a kit for him. My Joker Poker is working fine with the electronic tilt, but if I ever sell it I'll put the plumb bob back in and keep the electronic tilt.

#80 3 months ago

Impressive engineering by Quench! I can't believe I watched this solution come about in real time. This is what makes Pinside awesome!

#81 3 months ago
Quoted from QuietEarp:

Impressive engineering by Quench!

I totally agree! This has been an unresolved problem for years! I searched the problem on different sites that dated back years and never found a solution. It's so much fun to be playing my game now and I'm tilting the heck out of it....just can't get over the fact that it's working now!

#82 3 months ago

Probably should get a write up perhaps even with a drawing and have marked as key post. I will be ordering parts with my next order.

#83 3 months ago
Quoted from Insane:

Probably should get a write up perhaps even with a drawing and have marked as key post. I will be ordering parts with my next order.

Annotated pictures would help.

#84 3 months ago
Quoted from JethroP:

Quench, you are a hero! Your solution works!!
Installed 10uF ceramic cap and 1N5819 as you suggested. Works every time. Even took out the metal bob and reinstalled my old graphite bob and works perfectly. I'm sure others will find this solution to their problem. No doubt Ni-Wumpf will now recommend this in the future. They should pay you a royalty/consulting fee for solving their design problem.
Thank again!!!

can we get a photo? thanks!

#85 3 months ago
Quoted from KenLayton:

Annotated pictures would help

Quoted from lint:

can we get a photo? thanks!

Something like this? Title suggestion?
IMG_5457 (resized).jpg

#86 3 months ago

Very cool you guys found a fix. What are the markings on that capacitor? It looks very small, more like a pico than a micro, and too small for a 10 uF cap.

#87 3 months ago
Quoted from Biffbar:

What are the markings on that capacitor?

Marked 106. That would be 10uF. Here is what I bought:

Screen Shot 2020-07-15 at 9.08.29 PM (resized).png
#88 3 months ago
Quoted from Biffbar:

Very cool you guys found a fix. What are the markings on that capacitor? It looks very small, more like a pico than a micro, and too small for a 10 uF cap.

MLCC type capacitors now-a-days are pretty impressive in size to capacitance/voltage rating. It would be a 106 cap code.

#89 3 months ago

This should also be added to the PinWiki site.

1 week later
#90 3 months ago

Any tips on getting Ace to respond to email? Same board which is acting dead. I need to know if it is gone or I can mail it in, etc. No responses at all. been 2 weeks.

#91 3 months ago
Quoted from lint:

Any tips on getting Ace to respond to email? Same board which is acting dead. I need to know if it is gone or I can mail it in, etc. No responses at all. been 2 weeks.

I called and emailed him for a few days before he contacted me back. All I can say is keep trying. BTW, what's going on with your board?

#92 3 months ago
Quoted from JethroP:

I called and emailed him for a few days before he contacted me back. All I can say is keep trying. BTW, what's going on with your board?

You can see the thread I created here: https://pinside.com/pinball/forum/topic/ni-wumpf-system-1-cpu-v1-board-issues#post-5754534

#93 3 months ago

I really appreciate the effort made by JethroP and Quench. I went ahead and disconnected and removed the prototype electronic tilt board from my Joker Poker and reinstalled the good old plumb bob. I used a nice new plumb bob with thumb screw from PBL along with the new diode and capacitor. The tilt now works perfectly I am glad to report. Now if only the foam ear plug trick would work on these old Gottlieb games without replacing the plumb bob hanger and shaft...

I like the original tilt mech better than the electronic one for a number of reasons. The electronic one worked just ok, but the software was in a very early stage and needed a lot of work to be a really good replacement for the plum bob. Being a beta tester, I wrote up a long list of things that I would change and sent them to the person who is designing the board. Unfortunately I am not sure he is still working on this project as I have received no response.

Edit: Here are the parts I ordered. Diodes and capacitors are literally a dime a dozen, so I figured I would order cheap assortments that had the proper values in them. This will give me enough to do a bunch of games and who knows when I will need some other diode or cap for an old Bally game or something? Anyway I found a diode assortment for $5 shipped and caps for $10.

amazon.com link »

amazon.com link »

#94 3 months ago

Those are good prices on those assortments of diodes and capacitors.

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