Issues: Fender Champion 600 Reissue - Pilot LED to #47 Bulb Conversion

Hello,

You need D5 to allow reverse current around the LED. I recall that LED’s can’t put up with much reverse voltage.

Assuming the LED you procured does NOT have a resistor integrated, you will need that resistor. Some LED assemblies have a resistor built in and don’t need the extra one in series.

What kind of LED is it and do you have the data sheet?

Re-reading the OP—are you replacing the LED with an incandescent bulb?

 

To fit an incandescent lamp, remove the diode and replace R24 with a wire link.
The lamp is fitted where the LED was.

 

I should have asked that first or read the title of your post! Ahhh the humiliation... glad you got it sorted.

EDIT: I’m still scratching my head as to why you were measuring 0vac with the lamp installed.

 

Because almost 6.3V was dropped across the current limiting resistor.

 

Ahhh so the cold resistance of the bulb must be pretty low say less than 20R?

 

Exactly. Whatever it is, it's a lot less than the 200 ohms it's voltage-dividing with. 20R would give you something like .6V, maybe you can measure that, maybe you can't - depends on the meter.

Power: W=V^2/R. Let's say it's a 1 watt bulb. 1= (6.3x6.3)/R

So the hot resistance might be around 36 ohm.... bupkis. Cold would be EVEN LESS!

EDIT - wow, what a guess - I oughta play the lottery. A #47 bulb is .945W, draws .15A.

OK so that bulb will NOT heat up with 6.3 V and 200R. It'd take 30V (plus 6.3 across the bulb) to get .15A through 300 Ohms - the bulb will be current-starved, never heat up, and still have its cold resistance as measured.

 

Another way to look at it is that the two lamp leads are essentially the same node (and therefore same potential) when there is barely any resistance between them. I’ve got it now Jeeves. Thanks!

 

Does anyone know where I can get a replacement jewel screw in fixture for my champion 600? I notice the fender deluxe reverb is to big.

Thanks