Chicago Coin backbox bulbs blowing out

[motibyte]

Hi everyone,

Got a Chicago Coins "Juke Box" pinball machine at a yard sale this weekend. Works ok, added a new chime assy because the previous owner removed the original for some reason. So now that I got that working was wondering if anyone had any ideas why my backbox bulbs are blowing out. Put a DMM to it and it reads 40.6 volts, that's for most of the bulb sockets. The "tilt" works fine and registers around 6.2 V when lit. Only 6.2 V are being fed at the subpanel to bacbox connector (blue\white wire) and when I test any bulb socket in the backbox by touching the primary lead and using the subpanel ground instead of the backbox ground I get 6.2 V. Any reason why the backbox ground would increase the voltage by 33-34 volts ?

Thanks in advance !

 

[carl lawrence]

Hi everyone,

Got a Chicago Coins "Juke Box" pinball machine at a yard sale this weekend. Works ok, added a new chime assy because the previous owner removed the original for some reason. So now that I got that working was wondering if anyone had any ideas why my backbox bulbs are blowing out. Put a DMM to it and it reads 40.6 volts, that's for most of the bulb sockets. The "tilt" works fine and registers around 6.2 V when lit. Only 6.2 V are being fed at the subpanel to bacbox connector (blue\white wire) and when I test any bulb socket in the backbox by touching the primary lead and using the subpanel ground instead of the backbox ground I get 6.2 V. Any reason why the backbox ground would increase the voltage by 33-34 volts ?

Thanks in advance !

sounds to me that there is a short some where,thay should not be 40volts going to any bulbs ,more like 5.6 - 6.2 volts
cheak your work ,you may have knocked a wire to touch a coil or something ?

 

[motibyte]

Thanks, the chime was added to the subpanel and the playfield still lights up ok, started looking in the backbox "after" I realized the lamps were being blown. It's weird for sure and I'm no expert, seems the ground goes in and out of all kinds of places.

 

[backbox]

I don't specifically know the jukebox, but other chicagos of the same era have a pretty standardised power supply.
blu/wht 6V and grn 0V to the backbox.

The transformers in these generally have output taps at 33 / 30 / 12 / 0 / 6V ac
although transformers aren't really plus and minus, notice that the 6V tap is on the other side of 0V to the other taps!

To get 40+ volts, the 0V wire to the backbox lamps must have become detached and shorted to the 33V tap i.e. you now have the difference between 'plus' 33 and 'minus' 6 = 39V
'cause you're measuring 6.2V, we can scale the 39V by 6.2/6 * 39 = 40.3 ... near enough

good luck

 

[motibyte]

Great advice, in looking for that short I found 2 of the subpanel->backbox connectors were mismatched\switched\mispaired, I switched them back and lights are on, voltage is normal. Now, when I press the credit button it goes through the startup sequence but the score motor just keeps spinning. Any thoughts on where to start troubleshooting this one ?

Thanks again !

 

[carl lawrence]

Mec on score reel sticking ?

 

[backbox]

hmm, tricky one without a schematic.
The motor has one supply connected to the ac and the other end is grounded by any one of numerous parallel wired scoring/control relays to complete the circuit.

The relays are triggered by events like tilt, bonus, out hole, chute etc. and are all along the lower edge of the sub panel.
If you can spot one of these energised that will give a good pointer.

Also, the score motor controls the reset positions of the reels and will keep driving until it believes they're set.
Check they are driven to zero. If not, they may be stuck or their solenoid wiring suspect.
Either way, try not to rotate them by hand as they're probably a bit crispy by now and easily broken. Operate their plungers by hand instead.

 

[Moonraker]

Great advice, in looking for that short I found 2 of the subpanel->backbox connectors were mismatched\switched\mispaired, I switched them back and lights are on, voltage is normal. Now, when I press the credit button it goes through the startup sequence but the score motor just keeps spinning. Any thoughts on where to start troubleshooting this one ?

Thanks again !

Go back to the mismatched connectors and see what wires were connected and are no longer then check to see if the colours match the area of the score wheel motor controls.

 

[motibyte]

Thanks guys, still new at all this but making progress. The "Lock" relay is energized when I add a credit and the Score Motor starts spinning but never ends. I found that by manually trigerring the "Reset" relay in the subpanel I can get the game started and everything looks like its working normally. There "is" a missing coil for one of the Score Reset Relays in the backbox that I need to replace. Other than replacing that missing coil, which I will, there's no way to bypass the startup sequence other than to trigger the Reset relay in the subpanel ?

Anyone know the startup sequence. ie.

Add credit, subpanel Lock Relay energizes, Score Motor spins and energizes Reset Relays in backbox causing score to be reset, if scores are reset and in their home position, then check next relay or next step ?

Thanks !

 

[backbox]

Ahh, that's a good find about the main reset relay!

Basically, the spinning score motor ratchets a switch which in turn pulses the score reset relays which in turn pulse the reel S.U. (step up) solenoids which ratchet the score reels until they reach '0'
The reels know when they're at '0' because wafer switches on the side of the mechs. have continually made contacts until the '0' position, which then open circuit the path to the S.U. solenoid.
Setting the reels to '0' by hand each time, we can temporarily ignore the missing score reset relay.

Now, the main reset relay!
In addition to the score reel wafers opening the path to the S.U. solenoids when at '0', there are others that close the circuit to the main reset relay (when all reels are at '0').

So .....
check all reels are at '0'
check continuity of the wafer switches at '0'. They may look ok, but check!

One gotcha is that the score reels will only step, and main reset relay trigger if the start relay is energised.

I don't suppose you have a schematic do you? It would be a big help