# Bachmann K27 Headlight LED:



## UK_Pete (May 13, 2009)

I bought the Bachmann K27 No 463 on Monday here in the U.K.
Now this question has probably been asked elswhere on the Forum at some point, but just how does one go about changing out a failed headlight LED (part no LEDXX 10058)?
I have two on order from Bachmann, one to replace the failed headlight LED (after just 1 hour of it being on) and one as a spare, (there is voltage getting to the terminals).
I know that some people scorn the colour of the Bachmann LED's but I can live with it.
I can get the headlight assembly away from the smokebox front and I know that I will have to unsolder the connections to the circuit board (PCB03), What I need to know is how to get the headlight apart without breaking it to remove the LED and fit the replacement?
Thanks in advance guys!
Regards,
Pete.


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## Curmudgeon (Jan 11, 2008)

If I recall, cut the wires, remove the assembly, place a small scewdriver up the hole where the wires go, leverage the reflector and lense out the front of the housing.


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## UK_Pete (May 13, 2009)

Thank you Dave (?), I just didn't want to break anything by going at it the wrong way!
Cheers,
Pete.


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## Curmudgeon (Jan 11, 2008)

Yeah, they don't give very good instructions on how to do it. 
I remember the first time I ever tried to get that style apart. 
All you have to do is remember it went together, so it has to come apart. 
If the light does not function, you may have to reverse the wires on the smokebox board. 
TOC (Dave)


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## UK_Pete (May 13, 2009)

Sorry Mr Curmudgeon Sir, but I'm guessing that you would be the one to ask if the ESU Loksound XL V:3.5 sound decoder really does just drop in the K27 without having to perform any major surgery or mods???
Regards,
Pete.


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## Curmudgeon (Jan 11, 2008)

No, I am not the one to ask. 
If I recall, the ONLY sound system in existence that would read the Sema chuff signal was the Loksound, but that was just published data. 

Now, if you want to know how to REMOVE that socket, re-wire the locomotive, install reed switch and magnets, incandescent headlamps, incandescent class lamps, strip loco-to-tender harness down to 4 wires per side, lock #1 and #4 drivers from wobbling side-to-side, replace counterweights and bypass most of the "With Integrated Production Electronics", then, yeah, I be he.


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## UK_Pete (May 13, 2009)

Yeah, Iv'e been there and read all your exploits, it frightened me to death!
I think that I might just give the Loksound a go soon when I empty my piggy-bank and report back here if it all works out OK.
Thanks again buddy,
Pete.


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## Crosshead (Feb 20, 2008)

Posted By Curmudgeon on 05/13/2009 6:06 PM
No, I am not the one to ask. 
If I recall, the ONLY sound system in existence that would read the Sema chuff signal was the Loksound, but that was just published data. 

Now, if you want to know how to REMOVE that socket, re-wire the locomotive, install reed switch and magnets, incandescent headlamps, incandescent class lamps, strip loco-to-tender harness down to 4 wires per side, lock #1 and #4 drivers from wobbling side-to-side, replace counterweights and bypass most of the "With Integrated Production Electronics", then, yeah, I be he.


Careful TOC! Next thing you know, people are going to stop believing you are anti-technology and think you actually do stuff like soldering. At least promise us you use an analog meter, and not an oscilloscope, or I am going to start thinking you might actually be "technical" after all. 

Richard C.


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## Curmudgeon (Jan 11, 2008)

I have an old Heathkit O-scope bigger than any microwave I have ever seen. 
Two handles on top just to carry the blighter! 

You did catch the bit about the inverted chuff, right? 

Simpson 260 Analog Voltmeter. 

I have a VTVM on the shelf. 

Hey, if I could hold a 637 class fast-attack at PD (periscope depth) + or - 2 feet in the North Atlantic, and do high speed angles-and-dangles, while keeping the SINS on-line for positioning, heck, I can do the technology bit. 

But when it comes to model railroads, I want some level of simplicity. 

I'll have to take a picture of my soldering iron someday. 
We used to use it to solder radio chassis together in the Vacuum Tube (valve) days.


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## nkelsey (Jan 4, 2008)

Ahh the good old days, when you sat around and waited for the tubes to warm up on the radio, just like waiting for Windows to boot.....


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## Curmudgeon (Jan 11, 2008)

I still have 4 or 5 fully functional radios. 
One is an old RCA upright in the front room. 
Had that one almost 40 years. 
Rebuilt a wood case Gilfillan several years ago, sits on the desk next to the upstairs computer. 
Got a Hallicrafters SW receiver, and then the 5-tube superhet in the dashboard of the 50 Ford. 
I know there is another one somewhere, just can't recall where.


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## George Schreyer (Jan 16, 2009)

LokSound decoders do a credible job at synchronizing the chuff to speed based on BEMF. I'm not saying that it is perfect, but credible.


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## Semper Vaporo (Jan 2, 2008)

Posted By nkelsey on 05/13/2009 8:07 PM
Ahh the good old days, when you sat around and waited for the tubes to warm up on the radio, just like waiting for Windows to boot.....


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## UK_Pete (May 13, 2009)

I had heard somewhere that the Loksound XL V:3.5 can read those K27 optical piston signals without any mods?
Thanks for your thoughts,
Pete.


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## Dan Pierce (Jan 2, 2008)

When replacing LED's I found golden yellow leds to have a nice glow like incandescent bulbs. These are available in 3mm and 5mm cases.


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## UK_Pete (May 13, 2009)

Thanks Dan, Do I need to know voltage/amperage for the LEDs?
I am sure that I could get replacements for them here in the UK, if I knew what I was asking for!
Cheers,
Pete.


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## Dan Pierce (Jan 2, 2008)

You meed yo know the supply voltage, and the bulb voltage. 
The difference is made up with a resistor. For 20 milliamps it is the difference voltage times 50 ohms, 20 volt difference for a 3 volt led on 23 volts times 50 ohms gives 1,000 ohms (1k). 
If the led is 3 volt and supply is 5 volt, then 2 volts times the 50 ohms gives 100 ohm resistor. 
For 10 milliamps, it is 100 ohms times the voltage difference. 
15 milliamps is 66.7 ohms. 

KISS used here, no led calculator is needed!!! 

for over 300 ohms, use a larger wattage resistor as they will get hot. 

Another point of confusion is the standard values of resistors. 
Numbers used for 10 per cent values are: 
10 12 15 18 22 27 33 39 47 56 68 75 82 91 100 follow this by a power of 10 multiplier (10, 100, 1000 etc.) 

If you are not sure, just post your led voltage and current specs here and your supply voltage and someone in the know will let you know about the resistor value and wattage needed.


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## UK_Pete (May 13, 2009)

Posted By Dan Pierce on 05/15/2009 5:09 AM
KISS used here, no led calculator is needed!!! 

Thank you for the valuable lesson Dan.
Now another siilly newbie question; what the heck is KISS?

Cheers,
Pete.


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## Curmudgeon (Jan 11, 2008)

Keep 
It 
Simple, 
Stupid. 

For the voltages we use, 220 ohm to 1K ohm. 
Botch....errrr......Bachmann typically uses 500 ohm to 1K ohm, and sometimes one resistance front and one resistance rear.


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## UK_Pete (May 13, 2009)

*K*
*I*
*S*
*S*

I guess I should have seen that one coming 
Thanks all,
Pete.


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