I have come by several of the Athearn ATH 90616 DCC adapter boards which I like for their ease of attaching the various wire leads while converting my older Athearn engines to DCC . However, there are several small black chips (Diodes?) at both ends, that seem to be for lighting, and which get very hot (scorching hot) when running the engine. I don't have lights hooked to the leads yet, but just running the frame, without the shell, around my main these chips get so hot I am worried they will melt the plastic shell or at least burn out. Is there somewhere I can find a wiring schematic for these Athearn boards and is it usual the chips get so hot, or what could be causing the heating? Thanks for any suggestons and links.Capt. Brigg Franklin CEOPacific Cascade Railway in HO gauge
Get an optivisor and trace out the circuit. I just Googled the adapter and it does not look very complicated. An ohm meter might help for tracing. I see the DC adapter plugged in. Usually four diodes form a full wave bridge rectifier, the first items DCC sees.
http://www.athearn.com/Products/Default.aspx?ProdID=ATH90616
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I would guess that the circuit is designed to have a load on it. Hook up some lights and see if that fixes it?
Yes, they are designed as a voltage drop. Two of them in series for a voltage drop of 1.4 volts. The bulbs are wired across the diode pairs. With no bulbs attached, the diodes are taking the brunt of the current flow.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Makes me wonder if that is for 1.5 volt bulbs which Athearn has used in their locos? I could not quite figure out how the diodes are used.
I just measured the voltage across the PC board light tabs and it is 1.6 volts, obviously for a bulb. This brings me to a larger problem of wanting to use LEDs for lights and they won't light up with 1.6 volts. I have to either cut the light wires coming out of the decoder, or find some way to bypass the diodes to get the voltage coming from the decoder onto the circuit board tabs. Surely someone has done this before, but it seems rather messy either way. It might be simplier to go streight to the NCE decoder and not use the Digitrax PC board. Suggestions and thanks for the above input.Capt. Brigg
If you are changing the bulbs over to LEDs, it's a whole lot easier to scrap the Athearn board altogether and start from scratch. By the time you figure out the board traces and where to modify it, you could have a straight decoder hardwired in and running.
A number of decoders today have onboard resistors that will drive LEDs directly without having to wire in your own resistors.