AMI Continental 2: Keyboard Letter and Number Backlight

[Deadhead Japan]

I have upgraded the keyboard letter and number backlights to LED.  I installed a direct replacement T-3 1/4 #47 bulb.  Over the past two days both the letter and number lamps have stopped working.  I replaced the bulbs and the bulbs stopped working again.  I do not know if this was a problem with the previously installed incandescent bulbs because the bulbs were inoperative when I got my jukebox.  I have noticed that the bulbs get really hot.  Not sure if the bulbs are overheating or something else....

The keyboard lamps are not in service manual schematics... These lamps are rated at 6.3V.  I know the AC voltage running through the box is at 26 VAC, with the exception of the turntable.  How are the 6.3V lamps powered if there is 26V running through the cabinet?   Can someone tell me if the two little transformers that are mounted just below the mechanism on the back wall are the step down transformers for the lamps?  If so, which ones go to what lights and what are they rated at?  Also, the plug on the selector on the right, is this plug for the keyboard backlighting?

Thanks in advance.

Neal

[jukenorman]

I don't think there are any diagrams showing the wiring. I suspect that the voltage is being dropped by a resistor so with much less current being drawn by the LED lamp the voltage at the lamp will be higher. Just measure the voltage without the lamp connected, that will show whether it's being dropped from the 26VAC - ohms law and all that!

Norman.

[Deadhead Japan]

Norman,

The I have measured the voltage... Using Ohms law I should have 4.5Vs at the socket. I have 26V on numbers and 2 volts at the letters... I am assuming at these bulbs are not wired in series, but both bulbs stop working at the same time. I am getting some continuity from socket to socket but not on every connection, which me think the bulbs may be wired in series. Do you think that it is the 150 Ohm 7W resistor for the credit lights? Looking at the illustrated parts breakdown, it appears that resistor is located on the selector near the latch relay? Thoughts?

Neal

[jukenorman]

Hi Neal,
I didn't really have my brain in gear for my previous answer, doh! These #47 LED replacement lamps are specified for 6.3VDC. I'm not sure if there's an easy answer! I've been using LEDs as replacement for fluorescents but haven't yet dabbled with the small incandescents but they are quite popular with pinballers.

Norman.

[Deadhead Japan]

Norman,

Still chasing down what powers the keyboard lights. I have acquired an aftermarket schematic someone has drawn (quite nice layout). It appears each respective lamp socket is powered by its respective keys it is responsible for lighting. I am fairly certain the the 150 ohm 7 watt resistor that is on the selector assembly is in fact the one that appears in the schematics for the credit lights (good continuity at 150 ohms). Depending on what side of the lamp socket from I take a reading is giving me different voltage values. 26 vs 5 to 8 volts... Still sorting it out.

Neal