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Lennart's Model Railroad Blog

About this blog

This blog is about my current model railroad layout project; The N scale "Summit" layout, which is a freelanced interpretation of the Southern Pacific Tehachapi tunnels and their surroundings. Or at least, that is what it is meant to be. What it will turn out to be is another matter. The banner photo above shows what I want to recreate in N scale.

Decoder swap

Electronics, signals Posted on Sun, August 07, 2011 16:04:18

The Digitrax DZ125 decoder I ordered when I had managed to burn the DN144 sound decoder (as told in the previous post) has arrived and been installed. It was an easy install and everything went along fine. Even if SW (Cotton Belt) 7292 does not give off any sound, it at least runs. Here is a picture of #7292 sitting in the siding, being overtaken by SP 4810 and 4827.

SP 6702, on the other hand, is a poor sight, as you can see in the next picture.

It does not run very well at all, and never has. When started it barely moves at all. It creeps and jumps forward, with an occasional nudge. But after a while it sort of warms up and runs quite nicely. I have tried a bunch of things, cleaning, resoldering the decoder etc but nothing seems to help.

So when I bought a new docoder (DZ125) for SW 7292 I though I should get one for 6702 as well. Yesterday I took out the TCS M4 decoder and installed the DZ125 instead. But no difference. The loco behaves as before. I’m running out if ideas.

Sound decoder mishap

Electronics, signals Posted on Sun, July 31, 2011 18:19:19

Work has continued on the sound decoder installation (Digitrax DN144 in an Atlas GP38). The first test run, with the decoder and speaker wired, but still “hanging loose” on top of the naked frame, revealed a problem (problem #1). The sound came on alright, but when moving forward the engine stopped and went silent, while first issuing three short beeps. It did not really stall. It more of made a controlled shutdown of itself.

If the engine was left were it sat, and with the throttle untouched, it soon started to move again. But after having picked up speed it stopped again. The problem went away when the sound was turned off (F8).

After some head scratching and some more test runs I finally decided it must be a power pickup problem. Apparently the deocder is fussier about uninterrupted power when the sound is on. Meticulous track cleaning made things better, for instance.

Time to install the capacitor, which I had so far left out of the equation. This since I could not figure out where to install it. But I could always solder it in place for a test run with the shell off.

Problem #2, the black capacitor wire was all of a sudden gone. Must have broken off during all the decoder and engine handling while running all the initial tests. After prying loose part of the decoder shrink wrapping I managed to solder a new wire to the decoder.

Problem #3, the red speaker wire fell off in the processm but it was soon soldered back, but I must admit my spirits were starting to fail…

But in the darkest of hours – success! With the capacitor in place the engin ran like a charm, where it earlier dropped dead every 10 inches.

All is good then you might assume. But no. Problem #4: At this point of triumph the capacitor which was sitting on top of the frame fell off and its legs shortened on the engine frame. Result = burned and destroyed decoder.

I have just ordered a Digitrax DZ125 deocder. The sound adventure is over for this time.

Frame modifications for sound decoder

Electronics, signals Posted on Fri, July 29, 2011 14:11:50

As some of you might remember (see this earlier post) I had the intention to fit a Digitrax SDN144PS sound decoder in an Atlas GP-40 engine. At that time I had no idea how I should manage to fit all the stuff (decoder, speaker and capacitor) into the engine. And I am still not sure if I will manage. Anyway, I thought I should update you regarding the status so far.

I soon figured out that the only place for the speaker would be in the fuel tank, facing downwards. A bit of the frame would have to go, to make room for it. I also decided to skip any ideas about a speaker casing. No space for that and me, with no previous experience of sound decoders, not knowing what would be required to make a casing worth while.

So I disassembled the locomotive and started to grind away at the frame, using my Dremel motor tool. The speed (RPM) regulator of the tool broke when I was halfway done so I did the last part using a Dremel bit in my drilling machine. Not very effective, but eventually I was done (I really need to get my self a new Dremel). Here is a shot showing the “hole” where the speaker will sit.

Not the neatest of milling jobs, but hopefully it will serve its purpose. I also made a hole in the fuel tank. I did not only drill a set of small holes for the sound to get out, but a large hole, the diameter of the speaker, so that the speaker fits inside the hole rather than behind it. In this way I gained the thickness of the fuel tank material and did not need to remove as much of the frame (hole not as deep as otherwise required). Here is the hole in the fuel tank.

Below is a picture showing how the speaker will sit in the fuel tank, flush with the bottom of the tank.

Last I made a groove in one of the frame halves, for the speaker wires. I also removed part of the frame at the very top. This to make room for the decoder.

The wire groove is the diagonal cut above the place where the rear truck goes. You might also notice that the top of the facing frame half is a little shorter than the other one (to the right of the text “Atlas”). I still need to do the same cut on the other frame half.

Signals at tunnel 16

Electronics, signals Posted on Mon, April 25, 2011 21:20:36

The signals at the other end of the siding, outside tunnel 16, are in place. As at the opposite end I had some clearance problems with the signal between the tracks (this time the dwarf), which forced me to place the signal farther way from the turnout than I had wanted. But it’s OK. No big deal. Here are some photos.

I have also strung some sewing thread between the telegraph poles. The idea was that it should pass as electrical cabling. I am not sure whether I like the result or not. I had to tighten the thread or it would curl in an unrealistic way. But now it looks to tight I think. Real wire sags a little under its own weight which mine does not. For the time being I will let it remain.

Last, here is a photo of two new cars – two PS-4000 Covered hoppers from BLMA Models. Really nice models with metal wheel sets, body mounted couplers and see-through etched metal roof walks. Click on it to see a larger version at higher resolution.

First signal test lit

Electronics, signals Posted on Sat, April 09, 2011 16:12:36

Today I placed the first signal on the layout and test lit it. Here is a train waiting for the signal to clear.

The clearance is a little tight. When laying the track I did not give enough thought to the fact that I needed space between the tracks for a signal. But it works even if it is a close fit when the hi-cubes pass, leaning inwards on the super-elevated curve.

The prototype avoids a similar problem by letting the siding curve around the signal as seen here – or perhaps there is another reason why the track curves as it does.

The signal remains to be bonded to the ground, and the electrical connections are still only temporary with the signal under total manual control (terminal strip and screw driver). I have not yet decided how to control the signals, so this was a quick fix just because I was eager to se the signals in place and lit. In the next picture I have managed to make the signal turn green.

Last is a side shot of the signal. This picture also gives a nice view of the rail size difference between the main line (code 55) and the siding (code 40), especially if you click on it to get a larger picture.

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