Dynaco FM-3 LED installation

So, with my new, bright tuning eye tube, my tuning dial lighting is looking pretty sad. It takes a 6.3 V #47 incandescent bulb. I would like to replace this with a nice, bright LED. The FM3zone folks have a kit, but they are out of stock. Has anyone done this conversion and if so, can you give me some details? Doesn't seem that it would be too difficult to do

Bill

You need to know the supply voltage (in your case, 6.3V), the forward voltage of the LED, and its current (which may be higher in brighter LEDs).  With that, you can use this calculator:

LED Calculator for single LED

Clicking on the ? icons will give you some estimates if you don't know those specs for the LED.

I run an LED pilot light on my preamp, based on a PAS-2x chassis, and have no problems with flickering; the heavily filtered DC filament supply on the PAS is responsible for that.  On an FM-3, whose filament supply is AC, you may have flickering on the LED.  This can be cured by driving the LED through a rectifier diode (a common 1N4004 is plenty) with a 10-20µF filtering capacitor.  Sample circuit:

http://geek.scorpiorising.ca/contrib/Geek/LED_from_6.3VAC.png

GP49,
Thanks. That is about what I expected. A resistor, a capacitor, a diode and the LED; simple circuit. The hardest part will be making up a small board to replace the old bulb fixture. I should have most of the ingredients on hand. The FM3Zone kit has everything on a small circuit board and only runs $12. I may wait till they get more in stock and take the easy road.

Bill

You could break open a bayonet light bulb with the same base as the #47, and solder the LED to its base so the diode is where the filament of the #47 would have been (facing the correct direction!) then install the small circuit board somewhere convenient and wire the twisted pair from the existing socket to the board.

Consider installing one of these
www.ebay.com/itm/Boost-Buck-DC-Adjustable-Step-Up-Down-Converter-XL6009-Module step down to drop 6.3V to about 3V.

So, what about trying to use #44/#47 bayonet base LED lights commonly used in pinball machines? They are the correct 6.3 V lamps that appear to work for either AC or DC. Don't know about the dropping resistor issue. They even have some that are flexible and can direct light to the side that would work great to put the illumination directly on the dial face. Such as:

http://bayareaamusements.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=BAA&Product_Code=LB-TEAL-44-FLEX

So the original bulb socket stays in place and it could be "plug and play." Might be worth a try?

Bill,
I also sold those same PAS3/FM3 LED lamp replacements, and now that I've sold all my inventory to TubeNirvana he has them,
bottom of this page . . . http://www.tubenirvana.net/pas3-spare-parts.html
the little circuit board is made to mount in the same place as the pilot lamp used to.
You can use any color LED you want, and set the brightness by changing the resistor value,
typically 1K but for dimmer light, use up to 3.3K or for bright use as little as 680 ohms

Thanks for the suggestion. I looked at that in my research phase. It seems to be designed to fit physically the PAS3 and I don't know how well it would fit in the FM3. Also, as I read the page, the kit is $12 with a $12 shipping fee which makes it a pretty costly option. The pinball LED runs $1.05, but with a $6 shipping fee. I'm going to give that a try. If it doesn't work, I'll try to fix up something with a broken #47 bulb base as suggested by GP49. Then again, I can just live with the dim dial illumination.

Success!! I just got the #44/47 led light from Bay Area Amusements. It took all of 15 seconds to take our the incandescent bulb and insert the led. Works like a charm and very bright. The really nice thing is that with the flexible leads, you can orient the led right behind the tuning dial. No flicker whatsoever. Not bad for $1.05! Too bad the shipping ran about $6 but in got from the west coast to me in two days. So if you want to replace your FM3 bulb with an led, I think this is the way to go. Bill