apollo 13 moon magnet problem

[pokermachine]

Would that wire problem be the cause of this transistor problem?
I downloaded a copy of clays repair guide... it seems to be a website grab and i need firefox to view the pages... are there better copies of the guide?

[beaky]

unfortunately the guide doesn't have a section on these magnet boards
 

[Homepin]

Beaky is 100% correct about the poor design....what were they thinking? I come across this type of thing a lot when I am redesigning boards - all I can surmise is that they threw these machines (all brands) together at such a furious pace nobody was too bothered about getting small details right - if it worked, that was good enough!

In any case - after you sort out the issue - I would strongly recommend adding a resistor from the point marked "pin 1" on the left side of R41 to ground - probably about an 82K should be low enough in value to hold the output FET (Q3) OFF should the wire or connectors have an intermittant issue in the future and high enough to prevent interfering with normal operation.

[pokermachine]

ok so tomorrow i will be working on this problem a bit more, my thoughts are to start from the main board on the j2..test the (d4 hold) and the (d5 on) with a multi meter.... not sure what to look for but im guessing if this will tell me the voltages... then test the 1q and 2q to see if anything looks odd... then test the q5 and q6... my guess is one of these switches is stuck on then powering the IRL540 to stay on too.... does this sound about right or am i on the wrong track?
What should i be looking for on the multimeter to tell me something has gone wrong with a part?

Adam.

[pokermachine]

ok after a day of playing here is where im at....
at the magnet driver board the yel/vio reads 78 v same with the blu so my guess thats ok as book says 50+
at the blu/wht 18 gauge at magnet driver plug i have no or very little power.. maybe 1v...
followed wire back to display board.... here i have 5v from the orn/yellow,5v from the blu/wht 22 gauge and 5v from the wht/brn/blk.
thought must be one of the q4 q5 q6 transistors as when i put a multimeter to them power was going through them all differently so changed all 3.
when i connect the magnet driver board same thing... magnet switches straight on!

any ideas what to test next?

[beaky]

ok after a day of playing here is where im at....
at the magnet driver board the yel/vio reads 78 v same with the blu so my guess thats ok as book says 50+
at the blu/wht 18 gauge at magnet driver plug i have no or very little power.. maybe 1v...
followed wire back to display board.... here i have 5v from the orn/yellow,5v from the blu/wht 22 gauge and 5v from the wht/brn/blk.
thought must be one of the q4 q5 q6 transistors as when i put a multimeter to them power was going through them all differently so changed all 3.
when i connect the magnet driver board same thing... magnet switches straight on!

any ideas what to test next?

did you replace Q3 again? it's probably cactus again.

on the blue white wire between the two boards you should have either 0 volts (when the magnet is supposed to be off) or +5 volts (when the magnet is supposed to be on) anything in between then you will overheat Q3

I would be replacing c4 if it is a 1uf tantalum capacitor.

It's time to make a test led. Add a 150 ohm resistor to the led leg on the flat side then connect the other leg of the resistor to J2 pin 13 (GND / Black) and the long leg to J2 pin 15 (blue/white 18 gauge)
you want to make sure you have Q3 disconnected, we want to check if the display board is working or not.

I assume there is a test to check the magnet in the diagnostics?
if there is then run the test, The test led should light when the magnet is supposed to be activated and turn off when the magnet is supposed to be turned off.

Let me know how you go.

[pokermachine]

Ok LED test all done and all works fine... led lights up and goes out.... not sure if this is because i changed the q4 q5 q6 transistors or everything was working well up to the magnet driver board... anyways from your test im sure all 100% and the problem now on the driver board... i will replace the IRL540 again... ordered some more and give it another shot.... as for the  c4  1uf tantalum capacitor... i bought another one... looks different tho.. one on the board looks like a yellow resistor where the one they sold me is a yellow mutant capacitor.. is 1uf 35v i think... that ok? do i still need to change over if the LED test was 100%.... my hope is by changing the 3x transistors and a new IRL540 will all work or still more bugs in the system????

Also found that someone had already added a resistor from the point marked "pin 1" on the left side of R41 to ground  but was rather low like a 25 instead of the 80 something that was advised... too low? change that too??

Thanks for all your help everyone.... lost with out it thats for sure!!!!

For future reference anyone else with same problem... coils will not fire in test mode with door open... two white buttons need to be pressed in by coin door to test moon, rocket anything coil related so if tests are not working, close coin door..... test on moon does not test the magnet only moon switches... i tested the moon by removing bottom board and hanging it out side of the cab.... later tested the earth and blu and white wire before the magnet driver board with same result.... had to play a game and manually set off magnet to test... couldn't find a test to run magnet.

[beaky]

if it is all working fine don't worry about changing the tantalum capacitor

and the value of the resistor should be fine, it just needs something there to stop the gate on Q3 floating.

glad you got it all sorted

 

[pokermachine]

So new IRL540 came today... soldered in place and same as before.... picks up ball but does not release it untill most probably the fuse blows as it has done so now...
So with Beakys LED test everything i thought was ok up untill magnet driver board as led switched on and off at correct intervals.... so is it safe to say problem is on magnet
driver board? What on the driver board would make the IRL540 lock to on position?

Lucky i orded 3x IRL540's this time 

[beaky]

does the magnet now lock on as soon as you turn the machine on?

the only thing i can see that could be wrong is the capacitor C1 has gone short  . But that shouldn't blow the transistor.

Replace C1 and do a diode check with your multimeter (with the wires disconnected) on D10 and see if it's faulty.

once you have replaced the cap and checked the diode try it again with the led hooked up as before in the test and see if the led turns off with the transistor connected. do this with out the fuse first and if the led turns on and off fine then try it again with the fuse.

If i had it here i would be testing it a bit differently, I would be bench testing it and substituting the coil and +50 volts for a 12 volt led lamp and +12v to save blowing transistors one after the other but I have the all the test gear here which makes things a bit different. I am not suggesting you try this, it just makes it harder to fault find when you are not set up for it.

what resistance is across the coil?

[pokermachine]

Yeah the magnet turns on when machine is fired up.
Took the board to the electronics shop and they did a test with 5v on the board and said the mosfet is working fine under tests...
just locks on when installed to machine, he tested the diode and that was ok as well,
not sure if the cap was checked but will buy a 100v one like in manual and try the test you suggested.

[beaky]

no probs.
I just need to know if the if the output from the main magnet board that goes to the gate of the fet is turning off when the fet is connected (pin 1 on aux driver board or J2 pin 15 on the Apollo display board )
it would be better if you connect it at pin 1 on the aux driver board
 

[pokermachine]

GOOD NEWS!!!!! I can now go to the moon!!! Thank you for all your help!!! when i took the board to be tested they told me the mosfet was ok but for some reason a zenner diode was on the bottom of the board was reading power both ways... changed that but left the IRL540 in place... still turning on magnet.
Took Beakys advise and changed the capacitor C1 over... they sold me a big grey 1uf 100v cap not a little yellow one but put that in... still nothing... changed the IRL540 again with new diode and cap and presto... i can go to the moon!!!
not sure if it was the diode or the cap but hey works 100% now!!! Thank you all for your input and Thank you Beaky for thinking about each question i asked to solve this problem!!! I have learned a lot about pinball problem solving and repair from fixing the machine myself... it was fun.... after i got it working 

[Caveoftreasures]

Well done Beaky. 
In my house we have a saying, "If Beaky cant fix it, no one can".  I have never had anything he couldnt fix. Well done Guys ! Great teamwork.

[beaky]

thanks for the kind words guys
glad you got it sorted
Mosfets are great most of the time but unfortunately most of the time they will die quicker than a fuse can blow especially in a high current applications.