# Bachmann 2-8-0 Tender Problem



## sandbarn (Feb 13, 2010)

Hi All,


I'm having a problem with a non-functioning LED on the rear of tender. My question is, How do you disassemble the lamp to get to the LED?


I've traced the voltage as far as I can (to the base of the lamp itself) and there is voltage there (about 12v). But I can't figure out how to get the lamp apart to get at the LED. I've looked at the Bachmann IPB for the tender. No help there. It's made of several parts but no suggestion of how they are put together (glue, snap, etc.). 


If I can get to the base of the LED and check the voltage, that should tell me if I need a new LED or just fix the wiring.


Any suggestions?


----------



## SteveC (Jan 2, 2008)

Lloyd

Can't say that I know anything about how to dissemble the lamp, but if it is in fact being fed approximately 12VDC then one of two things; 1) if it is an LED then that is why it is no longer working (12V is way too high for LED's), and the voltage supply should be checked before hooking up a new LED to it, 2) at 12VDC I would expect to see some type of incandescent lamp and not an LED.


----------



## SteveC (Jan 2, 2008)

Lloyd

In taking a look at the Bachmann exploded parts diagram on their web site (i.e. link below), and taking a look at page 4 where the 2-8-0 Consolidation tender is depicted (i.e. see excerpt image below).

Bachmann 2-8-0 Consolidation Exploded Parts Diagram PDF[/b]










In looking at the above diagram, it looks like that you need to remove the lens first, which I'm sure is glued in place so you'll need to be careful in how you do that. Next, providing that there is enough slack available in the wires you remove the lamp a reflector and then separate the two so you can check the lamp to see if voltage is actually getting to the lamp. All the previous hinges on the fact that the diagram matches the actual equipment you have. Hope the above is found to be of some help.









I guess that if the lens is too hard to pry out without damage, you might be able to drill one or two small holes in the back of the lamp body and then using some small diameter wire (e.g. paperclip) and push the reflector forward until the lens is popped loose. ???


----------



## East Broad Top (Dec 29, 2007)

Pull the headlight off of the platform by gently squeezing the two "legs" of the lamp to snap it out of the base. Then take a small screwdriver and insert it into the bottom of the headlight. Gently push the blade of the screwdriver forward to press the lens and reflector out of the headlight housing. Pop the LED out and do what you need to do. 

Personally, while you've got it apart, I'd replace the LED with a "warm white" LED that's a lot more realistic in color than the orange LED used by Bachmann. There are a few different sources for them. I use the warm white LEDs from strings of Christmas lights, though it's the wrong season to zip over to Home Depot and pick up a string of them. (Perhaps next month???  

@ Steve - If I recall, the rear light on the 2-8-0 tender has a dropping resistor right near the headlight. It's shrink-wrapped just underneath the tender shell if I recall correctly. 



Later, 

K


----------



## sandbarn (Feb 13, 2010)

Thanks Steve and Kevin, 

I got it appart using the "drill a hole" technique Steve recommended. I tried getting something through the wire hole in the bottom but was affraid to put much pressure on anything because I didn't know what was inside. When I did get it appart I checked the voltage at the base of the LED and it was almost 15 volts (I suspect 14.8v since that's my battery voltage), but still no light. Guess it's time for a new one







!

Including some pictures of what I did. Maybe it'll help someone else.
I drilled a hole in the gottom of the lamp housing using a #60 bit (This picture was taken after everything was appart.).











I used a dental pick to reach through the hole and pop out the lens. That was about it. After that I just wiggled the wires from the bottom and the reflector and LED came right out.










If anyone is intrested this is what a bad 5mm LED looks like. 










Thanks guys. It's time to get on line and start ordering..


----------



## Del Tapparo (Jan 4, 2008)

Well that's what a good LED looks like too. When I have fried an LED, they get crispy and dark and brown. That one looks fine. I am assuming the brown is from what appears to be a board in the background. If you really have 15V at the base of the LED, it may now be an open circuit due to the failed LED. But personally, I don't think I've ever seen a failed LED in the last 40 years. They either don't work because they were installed backwards or fried due to over voltage. As mentioned above, there is a dropping resistor somewhere, and it is usually shrink wrapped in black. Could that be it right next to the LED? You might have a bad LED, but you might also just have a bad connection right at the LED, thus you measure 15V, of which no current is getting to the LED. (Just thinking out loud here).

I would certainly replace the LED, but I would also want to know where that dropping resistor is before I did it.


----------



## Dan Pierce (Jan 2, 2008)

SteveC If a 12 volt source is used with a 1000 ohm resistor to feed the LED from a circuit board, then the leads of a led will read 12 volts as there is no current drawn through the 1k resistor. 
An open led will always read the source voltage feeding the dropping resistor.


----------



## SteveC (Jan 2, 2008)

Posted By Dan Pierce on 06 Jun 2011 06:31 AM 
SteveC If a 12 volt source is used with a 1000 ohm resistor to feed the LED from a circuit board, then the leads of a led will read 12 volts as there is no current drawn through the 1k resistor. 
An open led will always read the source voltage feeding the dropping resistor. Dan

Thank you, sorry if I gave the wrong impression, however I am fully aware of open circuit voltage measurement. I simply assumed (yes, yes, I know) that Lloyd did also.









And since I don't have the product and wasn't sure the device is in fact an LED, and Lloyd didn't mention encountering the supposed in-line resistor I thought it would be a good idea to check before just hooking up an LED.


----------



## sandbarn (Feb 13, 2010)

Steve, 
The LEDs do have 1k resisters in the circuit. I added these myself after removing all the other wiring in preperation to install the ESC I got from Tony. The tender LED did work for about 1 hour of run time, and the front LED is still working. I have some (10) on order from Model Train Software.


----------

