Outhole solenoid stays energized

[mhbr549]

OK, after having put in a new MPU board and fixing the sound issue on this Stern Meteor and playing the machine for hours, it has suddenly decided that it wants to blow the fuse on the underside of the playfield and the outhole solenoid is staying energized at all times.  It might be coincidental, but it seemed to occur at the very instant that I hit the score to win a game.  Because of this, I was suspect of the knocker solenoid so I disconnected it and it still does the same issue.  I don't see anything obviously wrong on the front or back of the driver board.  Any thoughts you could offer would be much appreciated.  Thanks!

[Homepin]

The outhole solenoid driver transistor is very probably shorted. It can happen in a split second and for no particular reason.

[Strangeways]

Do you know how to read schematics ? It might be the driver transistor which has shorted. You need to find out which transistor is corresponding to the outhole.

Schematics are here ;

http://mirror2.ipdb.org/files/1580/Stern_1979_Meteor_Schematics.pdf

Looking at the Solenoid Driver schematic - "outhole" is Pin 8 of J5 - which is Q16.

Use a multimeter to check if it is shorted.

[beaky]

+1 on all of the above.

you will need a TIP102 transistor to replace the faulty transistor at Q16

[mhbr549]

Thanks for the replies all.  Using the multimeter, how can I tell if the transistor is shorted?  Please forgive my lack of electronic skills on this one. 

[Boots]

Thanks for the replies all.  Using the multimeter, how can I tell if the transistor is shorted?  Please forgive my lack of electronic skills on this one. 

Put your multimeter in diode mode and place one of the leads on the centre leg of the transistor and one on an outer leg (then the other) to test it, you will have a reading on the multimeter.
Compare the suspect transistor to the nearby ones of the same type.

[mhbr549]

Can I test the Q16 transistor while it is still on the board and get accurate readings?  Also, is it weird that this happened while the ball was in play on the playfield, not when it drained, and at the same time the knocker should have fired (which it didn't) when I hit a game win score?   Thanks!

[mhbr549]

OK all,  I tested the Q16 transistor and it was bad as you suspected.  Radio Shack did not have the TIP102, so I had to replace it with a TIP120.  All seems to be working, but will the TIP120 transistor be acceptable long term and do you think it will hurt anything?  Thanks again for your help.

[Homepin]

TIP102 and TIP120 are both NPN Darlington Transistors with the same pinout (base, collector, emitter - in that order, from left to right).

TIP102 is rated at 100Volts 8Amps
TIP120 is rated at 60Volts 5Amps

In this case your replacement (TIP102) is a higher rated part both in voltage and current and is in an identical package with identical pinout so it is a superior choice over the orginal.

These days the price difference between TIP102 & TIP120 is almost nil so it makes sense to use the better part. In the olden days the price difference was substantial and that's why manufacturers used the lowest rated part they could get away with especially when they were using 20 or so pieces per machine - the savings would have been substantial.

As for WHEN the transistor actually shorted - please re-read my original post:

"The outhole solenoid driver transistor is very probably shorted. It can happen in a split second and for no particular reason."

Electronics is a funny beast - you don't need to hear a grinding bearing noise for weeks before your gearbox siezes - it just happens, parts blow up and often there is no particular explanation that you can actually pinpoint!

[mhbr549]

The replacement transistor is the TIP120,  not the 102.  That being the caae, it looks like the new one is actually inferior to the original if I read your post correctly?

[Homepin]

The replacement transistor is the TIP120,  not the 102.  That being the caae, it looks like the new one is actually inferior to the original if I read your post correctly?

Yup - my mistake. The 120 will be OK until you source some 102's or better.

[mhbr549]

I'm actually thinking about replacing the entire driver board with the Alltek board since I have the new Alltek MPU already in there.  Do you think that would be a good move?  I'm not sure what experience anyone has had with the Alltek driver boards.  On another similar note, I had to replace the resistor on the upper flipper with a 10w instead of 5w because it's the only thing Radio Shack had in stock today.  It seems to be working fine, but do you all think that will cause any problems?   Sorry to keep hounding you guys with questions, but this thing is all new to me.  I do very much appreciate you all giving me the benefit of your experience though!

[Homepin]

using a 10W in place of a 5W is perfectly OK as you are using a part with a HIGHER rating. The other way 'round is no good - IE - using a 5W in the place of a 10W - the 5W resistor would either get VERY hot or burn out if the load demanded a 10W. So in your current case you can leave the 10W in place forever if you wish.

I am not a fan of the Altek driver board for one very simple reason. The output transistors that you are having problems with right now on your old board are surface mounted devices on the Altek board. Granted, they are upgraded types being MOSFETs but if you have a problem with one of them I would like to see you repair the board - you virtually can't so the board becomes a write-off.

I would stick with the discreet, through hole board you have now and repair it with the correct transistors - these parts are easily available from many suppliers including me.

[mhbr549]

Great Information!  Thanks for all of your help my friends.  As of tonight, my old Meteor machine is shooting the ball, flipping the ball, and playing all the sounds.   All thanks to my new found friends on this forum.   

[beaky]

well done on the repair

It would be a better option to overhaul / rebuild the driver board than to replace it.
But if it is working fine then leave it as it is.

I would never put a board with surface mount devices in any of my machines.

I think it's time for a Home pin, Stern / Bally driver board to come into existence.