Burnt out denomination, coin in/accepted circuit?

[tjankovs]

Hello...

I wanted to replace my denomination and coin in bulbs with LEDs to get rid of the yellow color.  I found these https://www.cometpinball.com/products/86-smd-bulbs and it appeared to be a good fit.  Installed one and it looked great.  A bit later the circuit is dead.  Any tips on what fried and why?

Thanks
TJ

[twinfire]

CHINA   

[Tilt]

Which one no longer works, the denomination or the coin-in ?  Did you replace both or just the one? 

There are some bulbs that may not be compatible with the bulb holder and can cause a direct short across the supply voltage, but in your case you say it lit and looked good until it quit.  If it was causing a short it wouldn't have lit at all.  Perhaps the LED was defective and burnt out?

[Stayouttadabunker]

Try a regular incandescent lamp, to see if your display sockets are still good.

[tjankovs]

Thanks everyone for the quick replies!  I started with taking 3 all incandescents out.  Added the first LED.  Looked good.  While changing out the other two holders I noticed the LED I added was out now!  I switched the installed LED back to an incadecent and it was still out.  Switched the remaining two back to incandecent and none of them work.  It appears the circuit is ground switched.  One power line and 3 switched grounds.  I just checked with my meter and get 0V power line to chassis.  Fried the supply somewhere.  Everything else is working.

Is this voltage sourced from the 'mainboard'?

Thanks for your ideas!

TJ

[Tilt]

Alright, well remove the MPU tray and look at R3 on the motherboard and see if it's  or not.  That's the series resistor for the denomination lamp.

[twinfire]

What about the fuses, are they still good?

[tjankovs]

Well...upon further inspection with my glasses on, the conductors on the bulb wrap around the backside.  When installed, and making good contact on both sides of the socket, it will result in a dead short.  When I first put the bulb in it was probably only partially contacting, then shorted. 

Time to check out R3.

TJ

[tjankovs]

It appears to have been replaced in the past, and a bit toasty now.


TJ

[Stayouttadabunker]

...When I first put the bulb in it was probably only partially contacting, then shorted...

Ouch!
The only way to use those LED lamps is to cut one side of the contact wire.
                                               Or
Throw them in the garbage can before you find more smoke!
 

[Tilt]

R3 is supposed to be 3.9 ohm, see what it reads with your multimeter.  That one looks like it got warm, but I've seen them a lot worse.

Here's an old thread that describes what the problem may be with the LED socket/lamp:


http://newlifegames.net/nlg/index.php?topic=8337.msg73090#msg73090

[tjankovs]

Yep...R3 opened up due to the short and my bad eyes (and beer).  The bulbs looks good now...no more yellow!  I do see a problem though, the coin accepted LED never goes off.  I am guessing a fried the transistor when the short was there and it is stuck on.

TJ

[Tilt]

As Homer says  , the cause of and solution to all life's problems 

See reply #13 in this thread.  The transistors are on the MPU board.  Actually the whole thread is a good short read.

https://newlifegames.com/nlg/index.php?topic=39061.msg206764#msg206764

[tjankovs]

Tilt...thanks for the link.  Q4 ordered and on the way.  Will report back.

TJ

[tjankovs]

Replacing Q5 fixed the 'stuck on' insert coin circuit.  Easy swap.  For reference the newer part is Littelfuse L401E3 TRIAC, SENSITIVE GATE, 400V 1A TO92.  $6 shipped from ebay.

[Tilt]

Glad it's fixed and working again.     for posting a suitable replacement part.

[Stayouttadabunker]

Excellent!
Thanks for posting your fix! 
Marking this thread as "Solved"