MTH Light Board

It’s just a 6 volt DC lighting board, track powered,1 amp capacity.  They were used in some lighting kits for dummy diesels, but with 8-10 6v lamps, it overloaded the board causing the regulator to shut down.  I replace the regulator with a 2 amp version.  Yes, they do get hot and should be heat sinked to the chassis with heat transfer grease.

Thank you Jon....I will see if I can change the regulator (black thing) to a 2amp version.

Is the missing section of the board critical to its proper function, as the other board I have (that is complete) has a series of "transistors" thingies on it??

From what you have explained, the 6V output of this board may still be too high for the red LEDs in the caboose tail lights.....is that correct??

Peter.....Buco Australia.

Couple of things about this.

It's a linear voltage regulator. These TO220 tabbed style regulators are ALWAYS going to get hot as you load them. Simplified- they are a voltage divider- effectively 2 resistors. Yes, more advanced in that they use transistors and regulate the voltage- but at the heat and power level- they are a voltage divider and waste a HUGE amount of power proportional to the load current. I'm saying this because when you see one of those devices- the rules inside your head about power and heat should kick in. They SHOULD just about always be heatsinked. They produce more heat the more voltage and current they drop. By that, I mean let's say your rectified DC is 20+V DC going in (~18V AC RMS), so if 6V is our regulated output, the regulator is dropping 20+ minus 6, at least 14 maybe 18V!!!!! And if your current is 500mA, well 500mA of 18V is, drumroll......... 9 Watts!!!!!

P_LOSS = (V_IN – V_OUT) * I_OUT

This is part of the reason why we often use switching regulators that use inductance and a different principle entirely on regulating voltage and not subject to the huge heat generation a linear style voltage regulator produces.

Again, just some basic rules: Resistors resist current, not voltage. That's why you have a regulator (especially when electronics are the load and/or the load may vary and change or is voltage senstive, not current only ) and not a simple resistor in series.

LEDs are diodes- as such, once they conduct- you need to limit current- AKA- a resistor in series with the LED.

I'm saying this- because you quoted ratings- without understanding that it's not magic- a 2A linear style regulator doesn't defy the laws of physics. If you have a high input voltage, and a low output voltage- you cannot reach 2A BEFORE hitting the thermal limit.

Net- changing the regulator to a 2A "beefier" one doesn't magically take away the heat.

If you want limited heat- use a switching "buck" style regulator

If you want to power an LED from a voltage source- your typically need a resistor in series with the LED to control the current.

If you use a linear regulator- heatsink that thing!!! Know the limitations of the device and the total circuit. The more voltage you put in, the hotter it will get. The more current you draw, the hotter it will get. If you have both high input voltage and current draw output- it will burn a huge amount of heat and likely burn up.

Peter...I jus finished updating a MTH PS-1 GP 38-2 that used that board to power 6 grain of rice bulbs and four leds. I retained the board and used it on two of the bulbs for cab light. I noticed they used a 100 ohm resistor in the led harness. Might be a good  value to try.

Richard

Thanks Vernon for the in-depth information about these regulators (black thingies). Good to hear from you again.

Some of the information is well above my pay grade, but I did understand a lot of what you said. Bottom line......I will heat sink that little sucker if I use it in my caboose LED upgrade.

Richard (Rppoind)....yes, I will install a 100 ohm resister inline to the red LED's in the caboose, and see how it goes. Thank you for the info.

Peter.....Buco Australia.

Peter, too bad you didn't mention the light board, I could have sent you a couple with that last package.

@Buco posted:

Thank you Jon....I will see if I can change the regulator (black thing) to a 2amp version.

Is the missing section of the board critical to its proper function, as the other board I have (that is complete) has a series of "transistors" thingies on it??

From what you have explained, the 6V output of this board may still be too high for the red LEDs in the caboose tail lights.....is that correct??

Peter.....Buco Australia.

That board will only drive 6v lamps.  You could add an external 100 ohm resistor to drive LED marker lights.  Some of those boards have a resistor with dual output, for incandescent and LEDs.  The Budd cars used one.

John (gunrunnerjohn).....I didn't know too much about these lighting boards MTH made until just recently. I was figuring on using one of the LED boards you sent me....if all else fails. By the way, the tracking shows they have landed in Australia, and I should see them in the next day or so.....watch this space!!!

Jon (Jon G)......I was going to see if it would run the two incandescent globes that came with the lighting kit (and grab irons) that were tucked away inside the body of the caboose, in a plastic bag. Looks like this may have been one of your (MTH) production samples that got disposed of in the Cabin Fever Auction clean-out.

Peter......Buco Australia.