Extreme heat from decoder in HO scale athearn loco

[ski]

Hello!

I have an HO scale Athearn P42 loco with the quick plug for DCC. I bought a Digitrax decoder, plugged it in and after  about 30 seconds of running, the loco shell above the decoder was very hot. I took the shell off and indeed the decoder was scorching hot. I thoght maybe it was the decoder, so I replaced it with a TCS decoder and it is still amazingly hot. It runs fine and responds to commands...

I have only N scale stuff normally so my HO scale experience is lacking, along with any real DCC knowledge. Is this heat normal? I keep thinking that the shell is going to melt. It appears to be related to the incandescent bulbs (instead of LEDs) used by Athearn for lighting...it does not seem to heat up much if I turn off the lights using Function 0. Any idea how to easily remedy this??

Thanks!!!
,

[wvgca]

The decoder should not be 'scorching hot', if anything it will be slightly warm to the touch ... the model [with onboard DCC plug] should not be of the 'brown box' era, and should be newer than that, with a reduced power draw on the motor inself ..

You only have the one light ?? [ when it's on]

[ski]

It one of the RTR locos in the newer type packaging. Three lights at the same time are on...the headlight and two ditch lights. If the lights stay off, the decoder is not hot (or even warm) at all. But when the lights come on with Function 0, is he decoder gets really hot.

[jdcolombo]

It sounds to me like the lamps are drawing too much current from the decoder.  I'd replace them with LEDs.  When I do a decoder installation for friends on an older engine, whether in HO or N, I automatically replace any bulbs with LEDs.  Usually, 3mm "sunny white" LEDs with a 1K dropping resistor work perfectly for headlight and rear light in HO scale diesels.  For ditch lights, it depends on how they are lit - do they use a light pipe from a separate bulb?  From the same bulb as the headlight? Are there separate bulbs for each ditch light?  But no matter, they can be replaced.  If a standard 3mm LED is too big, you can use a 603 surface mount LED, which is tiny (or even the larger 1206).  Also use a 1K dropping resistor for these.

John C.

[ski]

Thanks to both of you for the replies!