I think this is a first for me. I’ve been having a problem with the rear light not coming on in an Athearn Southern engine and after checking wiring and bulb I notice this little burn spot on the decoder. I think it’s fried and could be the problem. What say you more knowledable decoder experts?
Jarrell
That’s definitely a burn, and it seems to be in the right area to kill the rear headlights as well.
,
Cooked’er up good, now add a side of grits and you’re all set.
Does that particular loco use low voltage bulbs and have resistors on the circuit board (which is how my RS-3 is set up)? If it’s just a 12-15V bulb with no resistors, this is probably what happened: bulbs have fairly high inrush current until the filament gets hot. This cna exceed the decoder’s rating. A resistor is often recommended even if th ebulb can handle the full voltage, unfortunately it tends to be a big resistor when it’s a 12V bulb. Low voltage bulbs using resistors already are fine.
–Randy
If the decoder still works, cut the plastic off and see what burned. If it’s a resistor, diode or capacitor, you can probably fix it yourself.
99.9% sure it’ll be the transistor for the function output.
–Randy
DH123’s are inexpensive. Not cheap, inexpensive. Save yourself the grief and buy a new one. I have a whole pile of these decoders running incandescent bulbs and have never ran into this before.
I have a couple of old Bachmann decoders that have Kentucky Fried lighting circuits. They still work fine for motor control and are in a couple of locos that have their lights hardwired to the power pickups. Eventually they’ll be replaced with Digitrax DZ125’s.
This pertickler sw 1500 has bulbs with no resisitors, as I recollect. It’s not here in front of me at the moment. Motor still works fine, front head light too, just not the rear. Take the decoder out and plug back in the dummy and both work, although kinda dim like. I guess if it had been in a steam engine I’d have let the smoke out, huh. [swg]
Jarrell
Perhaps a short in the wiring for the rear bulb? Not enough to be a dead short but certainly enough to overload the decoders light circuit.
I did that once when I wasn’t careful enough about my bare wires and I got a short across the function output and the magic smoke for that function escaped. The rest of the decoder still functioned fine.
Be careful what you wish for. When I shorted my Spectrum GW, you could’ve sworn I was bleedin’ the cylinder cocks for the fact that it was coming from the tender. Oh, and the annoying burning. plastic smell. Think the decoder’s fine, but cooked the board it plugs to nicely