Subbing LED's for miniature incandescent

[62vauxhall]

Next week, I am receiving a NAD 502 CD player - it's free. Supposed to play fine, be in good shape outside and has the remote. Only issue is dead bulbs in the display. I had a 513 changer for a few years a while back with the same problem. The 513 had a single bulb and Although I cant remember specifics, what I used needed higher voltage than what was present so it was dim. The display was readable but only close up.

According to the 502 SM, there is 15 volts feeding two 16 volt 3mm bulbs. Since I have not yet found any such animal locally or online, substituting LED's seem like a good idea.

All I know is that the LED's I can get my hands on easily will be 3.5mm 12 volt.

As mentioned, the supply is 15 volts so what do I do or need to know to calculate the value of the resistors I'm going to need if the LED's are 12 volt?

 

[Gepetto]

Next week, I am receiving a NAD 502 CD player - it's free. Supposed to play fine, be in good shape outside and has the remote. Only issue is dead bulbs in the display. I had a 513 changer for a few years a while back with the same problem. The 513 had a single bulb and Although I cant remember specifics, what I used needed higher voltage than what was present so it was dim. The display was readable but only close up.

According to the 502 SM, there is 15 volts feeding two 16 volt 3mm bulbs. Since I have not yet found any such animal locally or online, substituting LED's seem like a good idea.

All I know is that the LED's I can get my hands on easily will be 3.5mm 12 volt.

As mentioned, the supply is 15 volts so what do I do to calculate the value of the resistors I'm going to need if the LED's are 12 volt?

If that 15V is AC, you need to rectify and filter it first. LEDs will not withstand the reverse voltage if it is fed by AC. That is the first thing you must determine.

 

[62vauxhall]

Ahhh....thanks!!

 

[62vauxhall]

It might be on the fringe, but I should have mentioned this also.

I stopped at a hobby store specializing in model RR who did sell 16 volt grain of wheat incandescent bulbs. They had flexible leads instead of wires and a lightproof coating on the bottom half of the bulb but I should be able to work around that. Problem was they're $30 for a 20 pack and $23 for 10. They did have a bag of loose bulbs behind the counter called "12 to 16 volt" for $1 each. Is anyone familiar with that term 12 to 16 volt? I thought he was describing random unknown voltages. Could be 12, could be 16 or anything in between. I have since found similarly described bulbs for sale on model RR hobby sites and am now wondering if that means suitable for 12 to 16 volts.

Anyone have any insight into these?

 

[marcok]

These items could be a solution . (Brawa 3401)
Tested and used many times (also on tuner Sony 5000 F )
https://www.google.it/search?q=braw...X&ved=0ahUKEwjclo-7s7nPAhUKExoKHbjWB4YQsAQIKw
These are leds with a diode and a resistor inside for 12-16V ac supply .
Ready to run .
Ciao
Marco

 

[62vauxhall]

Thanks Marco but it looks like the 15 volts is DC not AC.

Reading Gepetto's post made me look at the schematic again. There does not seem to be AC of any kind going to the circuitry as all feeds from the power supply are after the rectifier. If that's the case then, to use an LED, I think all I need to do is drop 16 volts to 12 volts with a resistor but need to know what values. If it's a factor, the original lamps are indicated as being 65ma.

I found an online dropping resistance calculator and using 15v as supply voltage, 12V as voltage drop across LED and 65ma as desired LED current, a 47 ohm 1/4 watt resistor would work.

However, I am uncertain what the term "voltage drop" refers to. If it means dropping 3 volts (15 minus 12) then a 200 ohm 1 watt is needed.

Since that calculator is worded "voltage drop across LED", it seems to me that the desired voltage present at the LED (12 volts in this case) is the value I should be entering.

http://pcboard.ca/led-dropping-resistor-calculator.html

I've been thinking about those model RR incandescent lamps I saw. Maybe they are intended to operate with between 12 volts and 16 volts but with varying brightness? If converting to LED will be problematic, I could try them. $1 each is not a tremendous cost risk.

 

[R1200S]

Not sure if this helps but might:

http://www.diyaudio.com/forums/digital-source/151297-replace-display-bulb-led-nad-cd-players.html

 

[grapplesaw]

Hi Gary
i have some 3mm round 2.5volt led's in clear if you need them let me know , no cost to you

 

[Gepetto]

Thanks Marco but it looks like the 15 volts is DC not AC.

Reading Gepetto's post made me look at the schematic again. There does not seem to be AC of any kind going to the circuitry as all feeds from the power supply are after the rectifier. If that's the case then, to use an LED, I think all I need to do is drop 16 volts to 12 volts with a resistor but need to know what values. If it's a factor, the original lamps are indicated as being 65ma.

I found an online dropping resistance calculator and using 15v as supply voltage, 12V as voltage drop across LED and 65ma as desired LED current, a 47 ohm 1/4 watt resistor would work.

However, I am uncertain what the term "voltage drop" refers to. If it means dropping 3 volts (15 minus 12) then a 200 ohm 1 watt is needed.

Since that calculator is worded "voltage drop across LED", it seems to me that the desired voltage present at the LED (12 volts in this case) is the value I should be entering.

http://pcboard.ca/led-dropping-resistor-calculator.html

I've been thinking about those model RR incandescent lamps I saw. Maybe they are intended to operate with between 12 volts and 16 volts but with varying brightness? If converting to LED will be problematic, I could try them. $1 each is not a tremendous cost risk.

Get stock white LEDs with no resistors and put a 680 ohm 1/2W resistor in series with one of the 2 leads. White LEDs have a forward drop of 3.3V. This will give you an ~18mA drive current. Most all LEDs are rated at 20mA.

 

[marcok]

Brawa Led bulbs are for AC , because the standard power supply for accessories in modelrailroading is : 12- 16V AC
Incandescent bulbs for model railroader generally has 12 - 16 V range .
There are many other manufactureres ; Brawa items are only an example and they are available in Usa and Canada .
Ciao
Marco
PS: I'm a model railroader and you can visit my personal page
http://lnx.3rotaie.it/wp/marcok/

 

[62vauxhall]

Hi Gary
i have some 3mm round 2.5volt led's in clear if you need them let me know , no cost to you

Thanks but I was in town yesterday and got 4 white LED's & 680 ohm resistors. I got the player yesterday morning and had to go into Vancouver anyway. Before I did anything I hooked up the player and other than the display bulbs it worked and played fine.

Once I had the LED;s I "breadboarded" one to test and worked beautifully but cooked it accidentally. Went ahead with the replacement and discovered that inserting the LED's and resistor's legs in the holes lifted the ultra, ultra small pads on the ultra, ultra thin traces and cooked another. Once I had the last 2 LED's and resistors soldered in place only one worked. So I removed the entire board to see the underside and found I'd damaged the enough of the traces there was nothing to solder to.

So onto plan B.

Since I was in the area, I got some of those model RR bulbs as well. They came with about 4" insulted leads but the wire diameter was so small, I could pull a pair through one of the PC board holes. Plus the insulated leads were long enough to reach alternate points with +15v/-15v. I bundled 4 bulbs in parallel for sufficient brightness, soldered them in place and the display was lit again.



The board inside is a nice pretty blue color.



Since the display lit up I put the player back together, stuck in a disc and nothing. Cover came back off and found the disc was not spinning when loaded. Found a blown 500ma fuse so went and got some. But after replacing the blown fuse, the spindle motor is still not spinning the disc.

WTF!!!!

 

[laatsch55]

Gary, you just can't catch a break can ya??

 

[62vauxhall]

Nope. As a kid my dad told me the family was cursed that way. My mother always said "expect the worst". They're both dead now but the legacy lives on.

 

[stuwee]

Brawa Led bulbs are for AC , because the standard power supply for accessories in modelrailroading is : 12- 16V AC
Incandescent bulbs for model railroader generally has 12 - 16 V range .
There are many other manufactureres ; Brawa items are only an example and they are available in Usa and Canada .
Ciao
Marco
PS: I'm a model railroader and you can visit my personal page
http://lnx.3rotaie.it/wp/marcok/

Marco, that's a wonderful set up you have Is that your son peeking around the cabinet? Cute picture!

Where did you find that 1/87th scale Fiat Cinquecento?? I need one for my collection

 

[marcok]

Stuwee,
thanks for compliments for my layout .
Anyway :
a) pics were taken 14 years ago
b) the boy is my son Francesco ( now he is 22 )
c) I have verified the brand of Fiat 500 ( probably
made by Brekina ) , but at present it is discontinued .
Probably you could find it on ebay.it or ebay.de.

Ciao
Marco

 

[marcok]

Now the only manufacturer is Busch .
Ciao
Marco