Space Invaders Flipper tips?

Mitsurugi-w

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Hey Guys!

I finally got my Space invaders pin up and running. All of the switches and solenoids appear to work with the exception of both of the left flippers. The switch on the flipper button is fine but it never fires either flipper. I shorted the two wires connected to the switch together and they didn't fire.

I want to try and figure it out tomorrow so I just need a few tips about where to look for this specific problem. Been researching like crazy since picking this thing up so it would make it an easier day for me. Thanks in advance.

Edit: Forgot to mention I can make the coils fire independently so I know the coils are good.
 
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Look at the back of the solenoid driver board. There may be a burned trace in the area of the flipper relay. It can be repaired with a bit of wire.
 
No burnt area on the pcb. It actually looks pretty clean besides the added fuse holder mod. Any other ideas?

If you've got power at the coils and you can make them work by grounding them manually then you know you have a problem with the path from the coils to ground. That path travels through the cabinet switch, the flipper relay and some connectors.

I would start at the driver board and ensure you've got ground coming into the flipper relay. If not, trace back through the connectors to find the problem. If you do then I would check continuity from the trace on the driver board connecting the the "output" of the flipper relay to the cabinet switch. If that's there you know the problem is probably with the flipper relay contacts. You can try jumping around the contacts to be sure. If that continuity is not there then you need to trace through the connectors going out to the cabinet switch.

EDIT: I changed my advice above slightly for better detail.
 
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So you're saying to bypass the relay to see if the flipper fires? I have continuity from the button to the sdb connector and from the sdb output connector to the coils. Maybe it is a bad trace on the sdb. Could the relay be bad for just one flipper?

Also, if I put the multimeter on continuity and place it in the flipper 1 output it measures continuity to both left and right flipper coils. What am I missing there?
 
So you're saying to bypass the relay to see if the flipper fires?

It's an option but I would only do that once you're faily certain the problem is with the relay contacts. I don't think you're at that point yet.

The ground for the flippers originates at the rectifier board (J2 pin 2). From there it connects to both cabinet switches. With the flipper switch contacts closed it then goes to the regulator/driver board (right flipper = J2 pin 1. left flipper = J2 pin 2). Then through the flipper relay contacts (right flipper = contacts 3+5. left flipper = contacts 4+6). Then through a molex header and out to the coils (right = J1 pin 9. left = J1 pin 8).

With that in mind I would set a meter to continuity, connect one lead to J2 pin 2 at the rectifier board and trace through the circuit in the order I've outlined above. When you don't find continuity you have found your problem. It sounds like you have done some of that already but it doesn't sound like you're checked continuity through relay contacts and possibly the headers on the board.

Maybe it is a bad trace on the sdb.

A bad trace seems unlikely but it could definitely be a bad solder joint at the flipper relay.

Could the relay be bad for just one flipper?

Yes. There are 2 sets of contacts inside the flipper relay. One for each flipper. I've seen flipper relay problems with only one flipper several times.
 
Can I test continuity through the relay? Doesn't seem to work even on the right flipper section. I can trace continuity all the way from the rectifier (actually pin 9 I think)to the relay on the sdb (when flipper button is depressed) and then from the other side of the relay to the coils.

I did notice that on the working right flippers, on the top flipper there is a diode between two eos switch contacts that appears to be cut off from the left side's flipper. Is this important?
 
Can I test continuity through the relay?

Yes, but it has to be energized for there to be continuity through the contacts.

I can trace continuity all the way from the rectifier (actually pin 9 I think)to the relay on the sdb (when flipper button is depressed) and then from the other side of the relay to the coils.

I would try bypassing the contacts in the flipper relay for side that's not working at this point.

I did notice that on the working right flippers, on the top flipper there is a diode between two eos switch contacts that appears to be cut off from the left side's flipper. Is this important?

I would have to see a picture to get an idea of what you're talking about. It could be a problem but I doubt it's causing the flippers to not work.
 
I went to jumper the relay and in the process found some cold solder that I missed on the relay contacts themselves. So I got the flippers working and then I blew some fuses. The previous owner bought the machine non-working and replaced the blown fuses with incorrect ones. I put some new ones in and its working good now. Just have to clean her up and replace one coil.

Thanks Lindsey!
 
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