Decoded ESU V4 LokSound 73199, 73100, LokPilot 54650 and Atlas S2 decoders

[nightmare0331]

Looking good Kelley! Do you mill the frames yourself too, or have them sent out to be machined?

I machine all of the frames myself (Kato N SD70M/SD70ACe, SDP40F, E5/8/9, F3/7's, PA/PB's...) on a manual Grizzly 0619 mill drill.

There's quite a few more photos of the process and piles of stuff on my fakebook page if anyone is interested...no, not a plug for work...just shows how the sausage is made a bit better.

https://www.facebook.com/dufordmodelworks/

Enjoy!

Kelley.
www.dufordmodelworks.com

[gatrhumpy]

So on the 73100 Select Direct Micro, for the bridge rectifier (the 4 items near the front of the board), I got a puff of smoke from two of them. What would cause the bridge rectifier to go up in smoke?

[peteski]

So on the 73100 Select Direct Micro, for the bridge rectifier (the 4 items near the front of the board), I got a puff of smoke from two of them. What would cause the bridge rectifier to go up in smoke?

What? Too much current going through those diodes.

Did they smoke while the decoder was powered from DC or DCC?  If only 2 smoked, that seems like the decoder was hooked up to DC power.  What exactly was the model doing when the magic smoke was released?  Or what did you modify/add to the decoder before powering it up?

[gatrhumpy]

I placed the locomotive on the track, it had a weird ringing/buzzing sound, and while doing that sound, I saw the puff of smoke. I looked closely where the smoke came from and two diodes for the bridge rectifier circuit (the front two close to the LED in the front of the board) have these weird bubbles off them.

[peteski]

I placed the locomotive on the track, it had a weird ringing/buzzing sound, and while doing that sound, I saw the puff of smoke. I looked closely where the smoke came from and two diodes for the bridge rectifier circuit (the front two close to the LED in the front of the board) have these weird bubbles off them.

Since this happened right after placing it on track, I assume it  was on DCC power, correct?

Where was the decoder installed?  Did you install it?

From what you mentioned so far, the likely culprit was a short of either the positive or negative output of the rectifier to one of the track pickups (maybe through the chassis?).

[gatrhumpy]

Yeah, DCC. And yes, the chassis front pickup I believe was touching one of the four rectifier diodes. Hence why two of them are fried and have a small bubble on them.

I installed it myself on an Athearn SD70. Next time, I will grind down that part (front left pickup on the Athearn SD70) of the chassis so that they don't touch. Kind of annoying that I just wasted $95.

[gatrhumpy]

Dammit! These board decoders suck! I checked ALL the resistances between the frame halves, the motor, light functions, etc. I took apart the frame halves to see if anything was touching between the halves. I stick the SD-70 on the track, and I got the same freakin' puff of smoke that I did before. There is a small cap near the front LED that I think when it comes into contact with the right frame it fries the bridge rectifier. WTF!

[gatrhumpy]

I think what I'll do next time is to forego the front frame pickups and use the rear ones.

[conrad]

Too bad for your misfortune.

One possible way to prevent blowing $100 a pop (no pun intended) is to use a 27 ohm resistor in series with the DCC supply.  This is the MRC method of testing decoders and has saved me over the years.   Another method is to initially use the programming track to test.  The idea is to limited the current available to the decoders.

It's not foolproof as I've still ended up smoking several decoders over the years.

conrad

[RBrodzinsky]

It is not the boards, per se.  They are not designed as a "one size fits all".  They are specifically designed for older Atlas and IM models, and fitting them into anything else (of which I have done many) requires ensuring that everything is properly isolated.  If anything is "too close", I tend to grind it out; and then ensure no extraneous frame contact with Kapton tape.  This includes the afore mentioned Atlas and IM models.

[gatrhumpy]

In the post with the picture for the 73100, if you look at the right, towards the front of the board, just to the right of the LED, there is a very tiny resistor that when it comes in contact with a frame half, will fry the bridge rectifier. That will happen especially if you squeeze the frame halves too tight. That is a bad design, IMO.

Now you can certainly fault me for wrong installation, and that's your right. However, like I said earlier, I checked the resistance between the frame halves, the motor, and the light outputs. All showed an open circuit.

This may not happen with Kato and Atlas engines, but it will for Athearn diesel engines. In order to avoid this, one has to cut off the rear 1/4" of protruded frame metal off the front chassis pickups. Basically that will render the front chassis pickups inoperable, so you have to use the rear chassis pickups. However, TRUST ME, it will save you $100 in decoders because the frames are too thick for the front pickups, and you will fry a decoder eventually.

[gatrhumpy]

I tried to post a picture of what I'm talking about, but can't.

[Steveruger45]

Sorry to hear you fried the decoder. 
I’ve done several locos (Kato and atlas mainly and a couple of fvm) with these boards and yes like Rick says you really do have to make sure the board components and/or contact pads that must not touch the frame halves are free and clear of the frame and/or insulated from the frame when assembled and not forget those components on the underside of the board.
Those little components on the underside at the front of the board nearly got me once too.
In one case the board would be clear when fitted into one half of the filed frame when inserted from the open frame half side, but would touch the frame if the board was to be pushed into place longitudinally (drop in style) when both frame halves were assembled together. 
In my case I caught it and did a bit more filing for the needed clearance Between the forward left and right side frame to board contact slots.
On another loco I hard wired the left and right frame pick ups to the Left and right side board pads with short wires soldered to some pcb inserted in the frame slots, in order to get it all in and keep everything clear.

In short (no pun intended) these boards were made for specific locos and can be fitted to many with some modification, IIRC it says basically that in the ESU informational blurb.

BTW you have to make a certain number of posts before TRW will let you post a picture.  The actual number of posts escapes me for the moment but in good TRW tradition someone will remind me.

[peteski]

BTW you have to make a certain number of posts before TRW will let you post a picture.  The actual number of posts escapes me for the moment but in good TRW tradition someone will remind me.

25 posts.

Yes, these decoders are far from perfect as they are a universal fit.  I mentioned some of those shortcomings or what I considered poor design features in my original evaluations in the beginning of this thread.

 As with any bare-board decoder retrofit into a model it is not designed to fit, extreme care is required to make sure that none of the components or traces contact the frames.

Even with Digitrax or TCS decoders which are designed as drop fit for some specific models I find that the traces on the bottom of the decoder are too close for comfort to the chassis for me to trust the solder mask coating (the green insulating layer on the PC board) to provide insulation between traces and the frames. I usually add Kapton tape to the decoder in those areas.

[gatrhumpy]

Just a warning about the Athearn SD-70/75: Don't install these without first grinding down the inside right front nub of the frame a lot. I ground down most of the front pickups on my SD-70 and used the rear pickups instead.