Atlas GP 38 with Loksound 58721 and independent number boards

[Jim Starbuck]

With a little light chassis milling the 58721 v5 Micro Direct worked nicely in this Atlas GP38.

I milled out the parts marked in black which left frame notches at the front that the decoder fit in for track pickup.
[ Guests cannot view attachments ]

There was 4mm of room at the back under the decoder for an 8x15 speaker in a homemade styrene enclosure. More material could have been removed but I chose not to.
[ Guests cannot view attachments ]

The front two pickup tabes engage in the frame slots. The motor tabs were clipped short and hardwired with short wires to the pads on the bottom of the decoder as well as the speaker wires. The decoder, motor saddle and worms were all assembled into one side of the frame then the other side laid on top engaging the other decoder pickup tab and motor saddle latches. The pickup strips and trucks were assembled as well.
[ Guests cannot view attachments ]

The number boards were cut into separate pieces with the on board LEDs lighting them and separate wired 0603 LEDs glued to the back of the headlight piece driven by AUX 3 and 4. Instead of desoldering the AUX LEDs, I soldered the magnet wired LEDs to the on boards then blacked them out with paint.
AUX3 (headlight) is mapped to F0, AUX4 (rear light) is mapped to F6 and the onboard LEDs that were originally headlight/ rear light are both mapped to F3 (number boards).
The AUX functions have dimming enabled but the number boards do not allowing nice independent control of the headlight and rear light.

/>

[peteski]

Looking good!
So this is why you were looking for the info about the AUX outputs on that decoder.

[Jim Starbuck]

Looking good!
So this is why you were looking for the info about the AUX outputs on that decoder.

Yes Sir!
Thank you very much for your help!

[peteski]

Yes Sir!
Thank you very much for your help!

You're welcome Jim.  Good to see those extra AUX outputs being utilized in an N scale model.

But your description sounds like you tapped your added-on LEDs off the on-board LEDs instead of using the round solder pads?  If that is the case, for this install you didn't really need the info I posted.

If you ran your LEDs in parallel with the on-board LEDs, the pair shares the same resistor, so they are running at reduced brightness.

[Jim Starbuck]

Yes, my original intent was to connect the wired headlight and rear light LEDs that I had already installed in the shell to function pads with appropriate resistors. In your write-up of the decoder you mentioned desoldering the onboard LEDs, connecting wired LEDs and using the stock onboard resistors. Since AUX 3&4 were extremely convenient being right there on top I decided to use them instead of the pads. The chassis was assembled at this time because I wanted to see if I could map the functions like I wanted as I hadn’t tried that before. The mapping worked fine so I tried to desolder the onboards LEDs but it seemed like I needed to apply more heat than I was comfortable with so I just soldered the wires to the onboards. There are two LEDs in parallel sharing a resistor but they are plenty bright.
I would like to extend the rear LED closer to the light pipe to brighten up the numberboards.
What’s your recommendation for desoldering the onboard LED?

[peteski]

True, it is a bit difficult accessing those solder pads on the bottom of the decoder.  Not much clearance there.

I also agree that unsoldering SMD components is not easy, partially due to the fact that nowadays manufacturers use lead-free solder that has a higher melting temperature than the typical lead/tin electronic solder.

There is plenty of clearance around the top LEDs. I think you will have good result using the CHIPQUIK system Joetrain59 found and let us know in this thread.

I have used it successful on several  occasions.  Just follow the directions in the kit.  Basucally you add flux and the low-temp alloy to the existing solder joints. The low-temp alloy mixes with the solder, decreasing its meltin temperature. It stays liquid long enough for you to remove the component.  Clever system.

I got mine from Digikey (since I shop there for other items).  Part# SMD1NL-ND .

[tehachapifan]

Another nice install!