Help build me a dial light for my old Fisher receiver

jabski

jabski

Vintage gear noob
Hiding engine has no schematics on this.
All 9 of the small lamps, along with the tiny pointer lamp, are not lit.
I don't know the voltage of the lamps themselves, and don't care if I use incandesants or LEDs.... Just something to light the dial face.
I was even hoping that I could find some already made LED strip and just glue it on the old board.
The wires going to the board measure 6 volts.
I've forgotten all of my electronics for classes, but I know this is a simple thing, it's just beyond me, in my old age..!
Thanks for any advice.
 

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Checked the fuses.all ok. The board is getting 6 volts, it's just that the lamps are all burnt out, and I have no way to know what volt bulbs they are.
I was just wondering if there was a way to rig up a couple of LEDs.....
Put gas in the car....
 

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jabski said:
Checked the fuses.all ok. The board is getting 6 volts, it's just that the lamps are all burnt out, and I have no way to know what volt bulbs they are.
I was just wondering if there was a way to rig up a couple of LEDs.....
Put gas in the car....
Click to expand...

If you've got 6VDC coming into the pads on the left, then the 9 bulbs are 6V bulbs. Or 8V if you want them to last longer. They're all connected directly across the 6V rails in parallel. Not sure what those 220 ohm resistors in series are for, but the pad in the middle with the little indentations in it would be at 3V 9with no load). And it looks like an 18 ohm resistor in series with the pointer lamp, so that is operating at a somewhat lower voltage.

If you want to replace the lamps with LEDs, you're going to need resistors in series with the LEDs. You *could* use one resistor where the 6V comes in, but it would be better to have a resistor for each LED. The value of the resistor will depend on how bright you want the LED to be (or equivalently, how much current you want to flow through each LED). Find the LED's operating voltage from the data sheet (typically around 2.1V or so for a white LED) and its maximum current (say 10ma). You can use this to determine the minimum resistance to put in series with the LED. (So for the given example, there will be (6-2.1) or 3.9V across the resistor, so minimum resistor value will be 3.9V/10ma = 390 ohms). More resistance will reduce the brightness...
 
Wbcn, I measured as AC. Is that not right? If I measure it as if its doc, the reading is not steady.
The pad in the middle is one of the attach points to mount it.
You say 3volt, 9 with no load.
Is the small rice size pointer bulb going to be 3 volts then?
 
jabski said:
Wbcn, I measured as AC. Is that not right? If I measure it as if its doc, the reading is not steady.
The pad in the middle is one of the attach points to mount it.
You say 3volt, 9 with no load.
Is the small rice size pointer bulb going to be 3 volts then?
Click to expand...

Oh, well if it's AC then that complicates replacing the bulbs with LEDs because they need DC.

I made a typo in the "3V 9with no load" - didn't press the shift key. The 9 is supposed to be a "(", so it should read "at 3V (with no load)" - but I was assuming DC. Since it's AC, the pad in the middle is presumably grounded... But it's not really clear why they felt the need to do that.

The voltage rating of the pointer bulb would depend on how much current it draws. For example, if it's 100ma, then there is (.100 * 18 =) 1.8V across the resistor, and the voltage rating for the bulb would be 4.2V or higher. For all we know, it may be a 6V bulb but they're just adding the resistor to make it a little dimmer...
 
Not sure its how god intended, but I used xmas tree bulbs to relight the SS Fisher in the shop... they were in series, so depending on how many are on a string divided into 120V is their ACV... used em in a RTR also cheap easy replacements...
 
Ha, that's a cool idea....
But what about the 6 Vac that I have going to power the bad lights that came stock?
Would Christmas tree lights work on 6 volts?
I like that......
 
A string of 20 would be 6V or so bulbs,, with 60 bulbs they would be 2V or so... Three 2V bulbs in series would be 6V, use 3 2v groups in parallel and your golden... you have to be a little inventive,,,
I would make a new board to use, save the Fisher light board for new bulbs if you find em...
Have fun...
 
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jabski said:
Ha, that's a cool idea....
But what about the 6 Vac that I have going to power the bad lights that came stock?
Would Christmas tree lights work on 6 volts?
I like that......
Click to expand...
Some do, depends how many are in a series string,,, 10/12V bulbs, 20/6V , give or take... different wattage bulbs will give different brightness at a given voltage...
 
I've installed once those adhesive led strips. They are calculated for 12V Dc at max brightness. I think from 6V DC, rectified with one diode and one capacitor, they will be too dim.

Also, I've seen that "warm white" leds, when fed by little current (to make them dim), use to turn to a greenish light, not very nice. I usually paint them with some nail polish to make them more diffuse and turn the color to a warmer tint.

You can try some leds... Just rectify the Ac with one diode and one capacitor, (google "half wave rectifier") 470 uf should work, and add 1000ohm resistors in series with each diode. If it's too dim, use a smaller resistor. Or fit one trimpot. to find the brightness you like, and then replace with resistors of that value.

Of course the easiest is to fit incandescent bulbs again.
 
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