Fish tales

[bonehead]

Hi all, I am trying to fix the left slingshot on my ft pinball. I have checked the coil, transistors and wiring and all seems fine but the coil won't fire. I have done some net searching and a couple of sites mention it could be one of the U chips (74s374N).
I have a couple ordered but am unsure which location to change on the cup board. It operates coils 1 to 8'i think.

Any idea which one it could be? I have tried looking at the schematics but just don't seem to be able to understand them.

Help please!! I need to fix this for my next meet.

Cheers,
Steve

 

[t-m]

Hi Steve,

According to the manual the left sling is controlled by transistor Q76, which is in turn connected to pin 16 of the 74LS374 at U5, it does control the first 8 coils.

 

[bonehead]

That's brilliant. Thanks for the help as I want to get this working. Once tenchipnarrives I will report back what happens.

Thanks,
Steve

 

[t-m]

If you've got a logic probe you should be able to stick it on pin 16 of U5 and check it pulls low when the left sling is supposed to trigger.

 

[bonehead]

I do have one but will need to dig it out. I was just going to try piggy backing the chip first.

Thanks

 

[Ronnie Dent]

Does it work in solenoid test?

 

[bonehead]

No it doesn't work in test. I tried piggy Back the chip but still nothing. I am going to change the transistors today to see if it makes any difference even tho when I tested them they test fine!!!

 

[Ronnie Dent]

I think? But check first if you ground the transistor tab it should fire the coil

 

[bonehead]

I will try that. Do I ground the tip136c transistor to the metal side rail?

 

[Ronnie Dent]

That should be okay Steve but check the pin repair guide first, also you should have the voltage at the coil all the time, the driver chip provides ground so with your meter on ground and one lug of the coil you should see the 50 volts or whatever it is.

 

[Ronnie Dent]

Have a read of this

http://pinwiki.com/wiki/index.php?title=Williams_WPC#Solenoid.2C_Flasher.2C_and_Motor_problems

 

[bonehead]

I have power at both sides of the coil around d 50v so will try shorting the tab on 36c to earth and see if it fires. I have spare transistors so can replace if needed. It has baffled me as everything so far checks out ok. I will report back.

Thanks

 

[bonehead]

Update.

Tried the shorting tip102 to Earth and coil fired slowly so decided to remove CPU and check further.
After testing q76 75 73 out of circuit and still testing good I decided to replace them anyway. Re fitted the pcb and powered it up, yahoo it is working so I gues even tho they teeter good they must have been flaky.

Thanks for the help a d links.

Cheers,
Steve

 

[smarty]

Nice effort all round, glad you got is sorted Steve.

 

[Ronnie Dent]

Nice one Steve glad you got it sorted

 

[LAZORIAN]

Nice one Steve!
Fish Tales is a great game glad you got it working