Need help fixing a flipper switch for a Bally Party Animal (broken diode)

[2PacMan]

I was trying to fix a non-responsive flipper switch last night and broke the leg off of what i think is a diode (the little blue thing in the pictures).  I know nothing about these.  Does someone know what diode this is and where i can buy a new one?  I know the pics are blurry, but I cannot get a better shot.  I guess i should clarify, this switch isn't for the actual flipper, but it's for the second set of buttons right under the flipper button that control the lane change lights and stuff like that.

[ChadTower]

Usually the diodes in that spot, if I understand it properly, is there to prevent a back spike as the coil's magnetic field dissipates.  That's what the diodes on some of the Williams WPC flippers are, I'm pretty sure.  That sure does look like a dinky little diode to be doing that.

[2PacMan]

Now i'm wondering where I can buy a replacement for the diode and what the value is (so i make sure i buy the right one).  I'm hoping maybe raido shack has one.  This switch isn't even connected to a coil, so i wonder if i even need the diode.  I haven't played the game since i broke it, as i don't want to ruin anything.  Any ideas?

[ChadTower]

It should say right on it what the diode's value is.  I'd double check the schematic to see if it is actually supposed to be there... could be a hack or a mod.  Are there other similar control switches that also have that diode?

EDIT:  now that I look closer, it might be a zener diode.  That's even more interesting as zeners allow reverse flow when the voltage is higher than its knee rating... in a situation where a regular diode fries, the zener just opens the floodgates.

[2PacMan]

yeah, the button on the other side has the exact same diode, so it's supposed to be there.  Never thought to look in the schematics for the value, i just checked the parts manual, but couldn't find anything.  I guess i could just bring the diode in to radio shack and hope the guy there knows how to read it and has a replacement.

[ChadTower]

I wouldn't count on the Radio Monkey even knowing what it is nevermind if they have it.  It's not a cell phone accessory or a DirecTV contract.

Is it broken off so badly you can't just solder the leg back down?

[shardian]

Why in the world would there be a zener diode on the microswitch??

As a matter of fact, why is there a diode at all on the switch. Shouldn't that be on the coil lugs?

[shardian]

Oh, and Radishack doesn't even have zener diodes.

[ChadTower]

Depending on the manufacturer, the diodes move around all over the place... it's not the coil diodes he's talking about here.  Those are always on the coil.  The signal line diodes are sometimes on the switch, often there isn't any, some machines have them on the driver board right near the transistor matrix.

[2PacMan]

The leg broke off right at the blue portion of the diode.  I could probably put a bunch of solder around it and get the leg to stick back on, don't know if that's a great solution or not though. 

If i could tell exactly what it was, i could order it online, but since i don't, I was going to see if radio shack would have it so i could compare them firsthand before i buy.

[ChadTower]

Are you sure it doesn't say right on it in tiny writing?  They almost always do.  Bust out a magnifying glass.

[2PacMan]

yeah, i'm sure it does...it has a black band on one end and it has really tiny writing on it.  I couldn't read it with my naked eye last night.  I was just hoping someone would see the pictures and know exactly what it was, since i assume they are pretty common.

[shardian]

Sorry, it doesn't work that way. the only thing you can really tell from looking at a crappy picture is maybe what kind of component it is.

[ChadTower]

I know guys that may know that part off the top of their head.

None of them are here, though. 

Check the inventory list on a flipper rebuild kit for that machine.  Could be there.

[Ken Layton]

That diode is part of the switch matrix and must be connected. It is type 1N4148 and can be substituted with type 1N914.

Here are the Radio Shack part numbers:

276-1122   Diodes, type 1N4148/914    package of 10  (around $1.50 a package)

276-1620   Diodes, type 1N4148/914    package of 50  (around $3. a package)

Remember diodes are polarity sensitive devices. The banded end is the cathode. So the banded end of the replacement diode will be connected to the same terminal as the banded end of the broken diode. While you're out and about getting these diodes, stop in at the dollar store and buy a magnifying glass. The markings on these diodes are very hard to see with the naked eye.

The replacement diodes will be a different color. Traditionally these diodes have a red glass body, but Williams/Bally got a bargain price on those blue ones.

[ChadTower]

 

[shardian]

i think this would be more appropriate:

 

Feel free to respond to my pin thread here or at KLOV Ken. I need a magic answer too!

[2PacMan]

Whoa!!  Thanks Ken, you're the best!  I see you help so many people on both message boards, it's amazing.

Thanks also to Chadtower and Shardian...guess i'm off to Radio Shack this afternoon.

[Ken Layton]

There should be an insulator of some kind between your "lane change" switch and the flipper end of stroke switch. This isolates the low voltage (5 volts) from the high voltage (50+ volts) of the flipper coils circuit. Be sure the machine is turned off (or better yet unplugged) when changing the diode so you don't accidently touch the diode or it's wires to the 50 volt coil circuit and blow out everything on the cpu board!

[2PacMan]

Just a followup, in case someday someone has a similar problem and is searching the archives....the switch works now.  That's all it needed was a new diode.  I also replaced the original battery with a AA battery holder from radio shack.  The original battery looked to be in great shape, but i know batteries that old are prone to leakage, at least this way I have peace of mind now.  I did have to re-set all of the settings though, because at first the game wouldn't coin up and I had to go in and change everything back to the factory settings.