Legacy Amtrak F40PH Number Board Brightness Fix & Cabbage Unit As Well

I don't really know this stuff. Isn't that a high value? Any heat to worry about? Is the voltage set up for bulbs?

Just sounds like a big value of resistor. It does look good from here though! Nice post.

The larger the resistor value for a given voltage, the lower the current and the heat.  The resistor value I used results in about .06 watts of dissipation, and it doesn't even get warm. 

LED's are current mode devices, and you control the brightness by controlling the current.  I dropped the current around 5x to the bulbs.  LED's are have fairly linear light output in relation to current.  So, dropping the current 5x dropped the light output around 5x as well.

Thanks for the info. 

Looks good John!

Nice.  But I still like the idea of a pot there... but apparently I'm the only one.  Still, I think lionel should send you a freebie led board so you can experiment... and we'll live vicariously through you...

Well, a digital brightness control would be crazy expensive for something like this.  A manual pot could be done, but it seems somewhat pointless.  Once you get this set, there seems little reason to revisit it.

i like the idea of digital control of the various leds... but i'm clearly in the minority.  I don't think the HW would be expensive but to do what I want lionel would have to spend money to do it, and then marketing is not clear for getting new sales:  "This new engine now has the option to individually dim or brighten all LEDs through command control -- flickering is even supported.  Imagine the possibilities!   Yes now you can have a dodgy number board on your layout all with the push of a button!"

Severn posted:

 I don't think the HW would be expensive but to do what I want lionel would have to spend money to do it, and then marketing is not clear for getting new sales: 

Easy for you to say.

Nothing is so easy as the job you imagine someone else doing.

You have to also have all the interface to actually control all these new features.

Just to put a "bow" on this topic, I put both the powered and Cabbage unit on the tracks to see how they looked after the intensity mod for the powered unit.  The Cabbage unit number boards were way too dim for my liking.  Even after the mod to the powered unit dropped the current 5x, the Cabbage unit number boards were much dimmer. 

In for a dime, in for a dollar, so I opened it up and checked out how the number boards were powered.  Turns out they're powered the same as the powered unit, with track power, a resistor, and back-to-back LED's.  When I traced it out, I discovered a 22K resistor for the current limiting!  Yes, that's not a typo, a 22K resistor!   Stands to reason why they're pretty dim, they were getting less than a milliamp of power!  I skywired a 5.6k resistor across the 22k, that worked pretty well.  So, I replaced the 22k with a 4.7k, the same as I used in the powered unit.  I used a lightly larger size resistor, the old one was a 0603 size, I used the 0805 size.  This gives a bit more power handling as it's passing four times the current now.  On this one I actually took the picture after the mod.

This is a different board design, it has a processor managing most of the lights, but not the number boards.  The Cabbage unit also uses a version of the RCDR board and not the full RCMC of the powered units or the other dummies I've worked on.  Interesting tidbit, but not important for the problem I was addressing.

What do you know, the two units now have similarly lit number boards, just the way I'd expect, job done!

As before, be aware if you screw something up, you've probably bought it.  The connectors are pretty small and pulling on the wires is the kiss of death many times, so you have to exercise caution.  I use husky tweezers  to work the connectors out.  Obviously, soldering on these boards requires something a little more sophisticated than your typical Weller 100/140 gun as well.

You put a lot of time and effort into this.Great job as always.Your expertise is appreciated here.Nick

I was looking at these the other day and wondering if they would be better then a regular old magnifying lamp? They are only like $39 so I wonder how good the picture would really be as opposed to the one shown in the ads? Here's a link to one, but there are others out there. I saw a youtube video of someone using one of these, but I think they had a much more expensive one, like maybe several hundred $$.

Nick, in this case, it was pretty easy.  Once I found out that they were track powered, I just had to locate the resistor and install the correct value.  As I said, the hardest part is getting to the resistor, you have to be careful with the little 1.5mm connectors, the wires are small and break easily if you yank on them.  For the powered unit, I'm glad I now know the wiring is really out of the way of the flywheel, that's certainly killed a lot of these.  That was the only red flag I saw looking inside.

Some thought was put into the lighting mechanical design on these, most of the lights are on the one board.  I suspect that makes it easier to build and test.

It is interesting that one resistor was too low in value, and the other resistor was too high in value.  There was a 22:1 difference in light output for the number boards between the two units! 

There's an old saying about the right hand knowing what the left hand is doing...

I'm happy with the final outcome, they look like they belong together now.

rtr12 posted:

 

Looks good, that might be something that would help me!  I ordered one.   I'm using a desk magnifier, but this would allow me to sit back more comfortably.

Someone either goobed the math on the needed resister or fed the wrong resisters into it...  i always thought the surface mount stuff was only done by machine but google shows otherwise.

Still prefer a different way:  the digital pot chips are pretty cheap and have serial line interfaces which is easy...  but no takers.

Nice job on the repair, John. Thanks for sharing the process. The disappointing part is that you had to do it in the first place. Sounds like the lot of boards was run off with the wrong resistor in the pick and place machine. It doesn't make sense the the value would be different on purpose. 

Since the lighting boards are a different design, I presume there were two bill of materials and a separate run to assemble them.  Obviously, since the number boards were powered the same way on both, they should have had at least the same value resistor you would think.  In any case, mine now have matching intensity on the number boards, and I feel a little better about what's inside having looked them over while they were open.

Lionel should provide free replacement boards as a minimum.

No one should have to do that level of surgery to repair their mistake.

I doubt that Lionel has enough spare parts to even consider such a move.  If the past is any indication, they don't have a ton of boards, they simply produce some excess stock and use it for spare parts. 

In any case, by the time you actually have done the work to get the lighting board out, the easy part is replacing the part.

You know it's just a bunch of ground/power lines into that board.  One could roll their own board here ... put a blue tooth on it, then their own remote to make send commands to it to do whatever (or from the computer).  As long as the  leds were all on from the command control side of the house...