Solenoids still fire incorrectly... *FIXED*

[gajaman]

Since buying my Space Invaders some of the solenoids have been firing incorrectly.

I know that the problem is not the MPU as I use a new Alltek replacement. I know the problem is not the solenoid driver board as having tried two boards I get exactly the same result with the same solenoids firing when each switch is hit.

I have checked the wiring from the MPU J4 connector and the SDB J4 connector and this is correct in that the connector pins go to the corresponding pins according to the schematics.

I have fired the solenoids manually by grounding the transistors on the SDB and comparing which transistor should fire which solenoid on the schematic and these are all ok.

Tell me if I'm wrong but based on the above I think;

my MPU is not the problem as it is new
the wiring from my new MPU to the SDB has not been miswired
the SDB itself is not the problem as two boards behave exactly the same way
the wiring from the SDB to the coils has not been miswired either

Could it be a problem that the switches are messed up?

To be honest I'm getting pretty stuck now, I thought it was the SDB but I guess not.

Thanks

[RichSorr]

This is always one of the most frustrating issues to me. Do they fire incorrectly during diagnostics? If you haven't already check wiring to the switch matrix or for shorts in the playfield. Does it only happen with certain coils?

[gajaman]

This one is drivng me mad, but is a good way to learn some new stuff I guess.

The coils fire the same incorrect way in the diagnostic test mode.

I've just been reading the Pinrepair manual and this suggests that a bad solenoid driver board J4 connector/pins or MPU J4 connector/pins could cause firing of the wrong coils. I've ruled out the pins as the MPU is new and both SDBs do the same thing so I guess I should check the connectors.

What I don't know how to do this. I can check continutity between the connectors by sticking one end of my DMM in one connector and the other DMM end in the corresponding hole in the other connector but this won't tell me if the connector is connecting well with the pins on the board?

How can I test if the pin is connecting nicely with the connector?

[RichSorr]

I would Ohm out between connectors, see if you have a bad pin. You could also go between the header pins between boards. If theres not a solid connection between the pins it should show. I really am not familiar with the Alltek boards, but you could try resetting the board and making sure all the switches are set correctly. If it is firing wrong in diagnostics I would lean towards MPU or wiring issues to the boards.

[gajaman]

Pinball Jim - Thanks, I really don't want to believe that it's the MPU as it has behaved this way since the MPU was brand new. It seems really unlikely that this would have been defective out of the box? I guess I want to try an rule everything else out before exploring this, it just seems so unlikley.

RichSorr - By ohming out you mean testing continuity right? I can check continuity from connector to connector by detatching the connectors, but how can I test if the connections are good with them connected to the board?  Should I connect them but not push them fully home and test on the visible part of the pins on the board? Would this not be likely to read as not connected when it may be when pushed fully home?

Thanks for the help

[Ken Layton]

I've seen broken connector pins inside the brown connector housings. Most of the time the broken pins were at the solenoid driver board end.

[RichSorr]

I would check continuity with the pins not all the way on the connector. You would have to go from the solder side of the boards connectors. If it is all the original connectors it might be worth the time to just repin them, the pins are less than 10 cents each and its a simple task.

As for the MPU board being defective...never say never. I've worked as a tech in arcades for 8 years and there have been numerous  times where I've recieved bad parts direct from the manufacturers. BUT lets hope thats not the case and rule everything else out first.

[gajaman]

Thanks guys, I'm going to check continuity tonight.

With the connectors, how are the wires attached, is a special crimping tool required?

[ChadTower]

Thanks guys, I'm going to check continuity tonight.

With the connectors, how are the wires attached, is a special crimping tool required?

A $15 hand crimper will do the job just fine.  It takes a little practice but once you have it down it's not very difficult.  It is difficult without the crimper but if you're going to have pinball machines you need to know how to do this.

[gajaman]

So, DMM in hand I set about the MPU and the SDB J4 connectors.

First I poked one end of the DMM in the J4 MPU connector where the wires go in and then checked continuity at the SDB J4 with the connector off the board, they all checked out.

Then I did the same but the other way round (SDB J4 attached and MPU J4 disconnected and they all check out as well.

So no breaks in wires.

As I was on my own to check that all of the pins were connecting on the headers I removed the SDB leaving just the J4 connected so I could get to the solders on the back of the board. I then poked one end of the DMM in the MPU J4 as above and checked continuity on the back of the SDB J4 solder joints, they all checked out.

About to give up I thought I should do the opposite for completeness, removing the MPU with just the J4 connected and checking continuity on the solder on the rear of the board. I got no continuity on pins 2 and 3!

Having looked more closely at the connector it looks like the end bit of the pin has snapped off leaving no contact with the header pin. I tried to bend the pins to get contact just to see if this made the solenoids fire correctly but I couldn't bend them the right way. Guess I need to order some pins!

The pins needed are tiny, I'm not sure if they are 0.62" or 0.93", I'm guessing 0.62" as there are larger connectors on other boards? Also, I guess they are female (assuming the headers are male). Is there anything else I need to specifiy to get the right pins? I'm trying to find somewhere in the UK so I can get them quickly, if I can't I guess I'll get some shipped from Marco's.

 

[RichSorr]

I believe those are .100 pins

[gajaman]

Are these correct?

http://www.mechatronics-onlineshop.co.uk/mse-09-b-254mm-crimp-terminal-391-p.asp

[ChadTower]

Don't pick and choose, order tons of male and female pins and a few connectors.  You will eventually need them and at least then you have them all.

[gajaman]

My pins arrived in the post this morning and I set about changing the two defective pins on the MPU J4 connector.

I was too cheap to buy a crimper (£20) so I used a pair of pin nose pliers which worked just fine.

Plugged it in and all is now well! All of the solenoids fire, and at the right time - Yes!

Amazing how much difference it makes having thumper bumpers that work! Also many sounds that
I haven't  heard before are now present. Don't know why this is?

Thanks for the help guys.