Bachmann 2-8-0 Head Light Failure

[nosamnod]

Anyone have any experience of curing faulty head lamps?  I have a problem with the 2-8-0 (lamp on front only in my case) but assume all of the DCC ready Bachmann Locos will be similar.

I am using a Soundtraxx Tsunami just plugged into the 8-pin socket on the Bachmann 2-8-0 circuit board and everything works fine - except for the head lamp, which originally worked OK but suddenly went out without warning after just a week or two of use.

I have replaced the lamp itself (with no success) and I then established that the original lamp is in fact still working fine anyway (on another loco).

I have traced the wiring right back from the lamp, through the connections in the ash pan and all the way back to the printed circuit board in the tender and have checked all the connections and solder joints. Everything seems fine so far as I can see - but still no head lamp.

The Tsunami itself seems fine, so I have ruled that out.

Anyone have any ideas? (I was going to say 'bright ideas' but that would have been a pretty rotten pun!)

[Tim]

nosamnod

One other check, are you able to read any voltage between pin 6 (White) wire
and pin 7 (Blue) wire  on the decoder plug when the headlight is turned on?

You should read ~12v at this point.  The blue pin7 is + The white pin6 is - .
If you do read a voltage then check that pin 6 is not broken or bent.

Another place that I have found problems is the headlight connectors in the smokebox.
I have found the wire broken inside the shrink tubing on one of the connectors, and
being held in place by the shrink tubing.

If you get the voltage and the connectors are Ok, then the circuit board is at fault.

I never use the circuit board in any loco I always hard wire.

Tim Anders
Souderton, PA

[nosamnod]

Thanks Tim - I'll check the voltage, etc. with my meter later.

Definitely not the connectors in the smokebox - they're now hard soldered (got wise to that one already).

If all else fails, I have a spare circuit board and can replace that.

[Jim Banner]

What was the headlight current draw before you installed the Tsunami?  Or since you still have the original headlight bulb in working condition, what does it draw now?

What DCC system do you use?

If the system voltage is a little high and the bulb resistance is a bit low for the type of bulb, it is possible to exceed the absolute maximum function current when you first turn the light on.  The absolute maximum rating is often two or three times the published rating (100 mA for the Tsunami) but is allowed for only a small fraction of a second.  The bulb current can be up to ten times as much as the rated bulb current when you first turn it on.  So it is not too hard to momentarily exceed the absolute maximum current rating of a decoder function even though the average or rated bulb current is only half or two thirds the decoder function rating.     

By the way, bad puns are okay as long as they help shed a little light on the subject.  What's that old saying?  "It is better to listen to bad puns than to sit cursing the darkness."

Jim

[Tim]

Jim

FYI the lights in the On30 2-8-0 are led's, and the resistors are on the circuit board.

nosamnod

If you need to replace the board, why not hard wire the decoder and eliminate the
problem completely.  Use a 680 - 750ohm resistor for each led.

Tim Anders
Souderton, PA

[Jim Banner]

Thanks, Tim.  I was mixing it up with the 2-6-0.  And yes, removing the adapter board is the best solution.

Jim

[rwiseha]

I had this happen to me,  it was turned off in the controller.
Several times I have to turn on the lights after no running the engine for a while.  Just an idea.
Rex

[pandprr]

Thanks for all the replies - although I'm no further forwards with this.

To recap: The lamp worked fine for a week or two but then suddenly went out whilst the loco was running. Diagnosis: something come loose. But nothing is.

There is nothing wrong with the LED (I've tested it).

Don't want to remove the board and hard-wire. Whenever I've tried that before I get all manner of running problems, even though all wired up properly (I have 30 years of experience of wiring up locos and 2 years experience of DCC - so no, it's not me....but I just don't get on with hard wiring.

The problem is obvioously in the tender - as the tender concerned will not operate lights on another 2-8-0 (which work fine with it's own tender attached).

Likewise, the tender from the other 2-8-0 (which operates it's own lights fine) will not work the lights on this one. Therefore it seems there is an additional problem in the loco also.

Now the only thing which can be wrong in the loco is the coonnectors in the ash pan (which I've checked - they're fine), or the LED is wired the wrong way round (it's wired red to positive lead of LED and black to negative lead of LED).  All my other Bachmann locos (6) have blue and green wires to the head lamp. This one has red and black.

I can try reversing that and can also change the circuit board (I have a couple of spares). But before I do, does anyone have any fuirther thoughts.?

Thanks - Don Mason (aka Nosamnod)