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WPC95 coil not working


robm

Question

I have done some power driver board swapping between MB and MM to isolate an issue, long story short, put the original MM board back in it, and the trough eject is not working - all other coils are.

 

There is 75V at both lugs of the suspect coil, if i ground the drive side lug, the coil fires.

 

If i disconnect J116 (pin 2 drives this one) and ground pin2 of J116 plug, the coil fires. If i plug J116 back in, and ground Q64 (TIP102), it does NOT fire. The coil is driven by Q68 (TIP36c), predriven by Q64 (TIP102), predriven by Q55 (5401).

 

I have replaced all 3 of the abovementioned transistors, with no change. When i measure voltage at the tab of Q64 (TIP102) is fluctuates and can't get a decent reading on the digital DMM - the other TIP102's around it all measure 75V.

 

SO, i am convinced it is a board issue (since the coil fires if i ground J116 plug, so can presume wiring to coil is fine), and the next step would be replace u7 (74LS374), which i understand to be the next step back from Q55 (5401) - is this the next best thing to try, or any other suggestions?

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WPC95 coil not working

 

I've had strange issues before and pulled my hair out saying it should be working.

Days later, reseated the ribbon cable and bam. Working.

And that was a Whitewater trough kicker.

 

Sent from my iPhone using Tapatalk

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Well this was pretty frustrating as i replaced U7, and same result.

 

So started testing voltages and connections again, and noticed that the 75V came on at Q64 when i wriggled J116. Turns out, the stupid IDC connector was intermittent - so when i had previously tested the wire for voltage and firing the coil, it was pushing the 1 or 2 strands that made a connection into the correct position, however, once the pressure of the test lead was off, the connection became very dodgy. Replaced connector and is all working well!

 

Sick of removing the power driver board!!

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Those IDC connectors (and KK connectors) are dodgy. They are not designed for repeated plugin/removal. The are meant to be plugged in and to stay plugged. Which begs the question of why they are being used in pinball machines, which require those connectors to be removed and plugged back in repeatedly :(

 

Michi.

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Those IDC connectors (and KK connectors) are dodgy. They are not designed for repeated plugin/removal. The are meant to be plugged in and to stay plugged. Which begs the question of why they are being used in pinball machines, which require those connectors to be removed and plugged back in repeatedly :(

 

Michi.

Just checked Molex Spec sheet for KK connectors

This is what it says.

 

Mechanical

Contact Insertion Force: 17.8N

Contact Retention to Housing: 36.8N

Mating Force: 10.7N per circuit

Unmating Force: 3.4N per circuit

Durability (min.): 25 cycles

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Those IDC connectors (and KK connectors) are dodgy. They are not designed for repeated plugin/removal. The are meant to be plugged in and to stay plugged. Which begs the question of why they are being used in pinball machines, which require those connectors to be removed and plugged back in repeatedly :(

 

Michi.

 

Welcome to the world of pinball bean counter's cost cutting. Unfortunately the later the model machine, the more you find this cost cutting. If you are seeing this and it annoys you on 90's Williams/ Bally machines I suggest you don't buy a post 2000 machine, it only gets worse only the problems haven't shown there head yet.

 

Add to this machines now being made predominately for home / domestic use instead of there original commercial use intention. Imagine how problems like this will happen on the machines made in very small runs when they hit the 20 year age?.

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Durability (min.): 25 cycles

 

Yep. It means that there is a very high probably that after plugging/unplugging 25 times, the connector still works. Thereafter, the probability drops off rapidly. (It's one of those asymptotic curves where failure becomes more and more likely, quickly approaching certainty.)

 

The problem is that, over the life time of a machine, the connectors a likely to be unplugged a hundred times or more. Do that, and failure is already quite likely, probably in the 5-10% range.

 

Michi.

 

- - - Updated - - -

 

Welcome to the world of pinball bean counter's cost cutting. Unfortunately the later the model machine, the more you find this cost cutting. If you are seeing this and it annoys you on 90's Williams/ Bally machines I suggest you don't buy a post 2000 machine, it only gets worse only the problems haven't shown there head yet.

Unfortunately, I do have a post-2000 machine. And one of the annoying things is that I've been having problems due to various connectors not making reliable contact :(

The little 2-pin plugs on opto boards are a sterling example. They don't cope well with the endless vibration.

 

Add to this machines now being made predominately for home / domestic use instead of there original commercial use intention. Imagine how problems like this will happen on the machines made in very small runs when they hit the 20 year age?.

Depending on the diligence of the manufacturer, yes, that could get really annoying :(

 

Michi.

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When Ken serviced all my IJ boards he also binned 2 ribbon cables. I guess both were also well passed 25 cycles. Also I assume 1 cycle is taking off & putting back on, so you only need to do it 12.5 times & you start looking for trouble.
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Also I assume 1 cycle is taking off & putting back on, so you only need to do it 12.5 times & you start looking for trouble.

 

Not sure how they count that. I would have assumed that 1 cycle is plugin and remove. But, either way, it doesn't really matter. The number is ridiculously low, whether it's 12.5 or 25…

 

I don't know what the duty cycle of ribbon cables is. But I imagine that it would not be a lot better, because these things also are not designed to be unplugged and re-plugged a lot. Besides, the conductors in ribbon cables are solid core, and solid core doesn't doesn't lend itself to being moved much at all. Before you know it, you have an invisible break inside the cable somewhere.

 

Michi.

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Not sure how they count that. I would have assumed that 1 cycle is plugin and remove. But, either way, it doesn't really matter. The number is ridiculously low, whether it's 12.5 or 25…

 

Besides, the conductors in ribbon cables are solid core, and solid core doesn't doesn't lend itself to being moved much at all.

 

Michi.

Sorry but all the ribbon cable I have ever used is multistranded, not solid core.

example here

http://au.rs-online.com/web/p/flat-ribbon-cable/2899896/

number of strands 7

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