Decoder replacement board hell

[Big Train]

Since the wife was away this weekend, I declared it Big Train Liberation Day and spent the entire time catching up on all the N scale projects I've started.

Among those projects was installing replacement board decoders in the Intermountain Cotton Belt SD45 tunnel and the MicroTrains Cotton Belt FT units. Being Cotton Belt was just coincidental though I'd prefer they were SP. One was a deal I couldn't refuse and the other was a present.

Let me also say I've installed a couple of dozen decoders and am fairly adept at doing this and making the necessary unforeseen modifications when they arise. So I figured about two hours for everything, then go work on some modules.

First, the SD45 Tunnel installation using the Digitrax DN166I0 . When I first attempted this in the Spring, while trying to "force" the decoder into the frame slots, the frame broke above the motor. No worries, it seems I have Intermountain on speed dial these days and a replacement frame was sent at no charge. While doing an autopsy, the Intermountain light board is significantly thinner than the Digitrax decoder. Run into this before with other manufacturers, no big deal....except for this one. I get it, it's how the manufacturer specified the dimensions, but to be this far out to prevent easy installation of a decoder?

Fast forward to this weekend and finish the installation. Knowing the frame slots need to be enlarged to fit the decoder, started widening the slots. I started with a small slotted screwdriver and realizing how fragile the metal is didn't want to push my luck and snap off the tabs. Was grateful the metal wasn't zamac....

Only that was partly the solution, the slot still needs made wider where it bottoms out on the frame. After two hours of tedious filing and test fitting I eventually opened the slots enough to accept the decoder with little force.  (Having learned my lesson from the first attempt....)

Problem was finding the tools to remove the metal. Seems I had nothing to do that efficiently, files weren't thin enough, or didn't have teeth completely to the end. Wound up using Flex-grit wrapped around an X-acto saw blade. Seems I was removing metal at a molecular level, but eventually got done. Then finished using a small drill on the Dremel to mill the slot. Yes, I know you shouldn't use a drill bit for this, but the situation was getting desperate.

The next day, worked on the MicroTrains FTs using the Digitrax DN163M0. Had to enlarge the cut-outs on the decoder to fit over the mounting tabs on the body. While bending the LED to fit under the light shroud, one of the leads from the LED pulled away from the decoder because there was very little solder on the joint. Oh well, use THAT decoder for the B unit...

Once the decoder was in place, bend the LED leads to fit under the light shroud. Only to find out Digitrax's LED lead wasn't quite long enough to allow the lens to sit in the frame without impeding the fitting of the light shroud on the mechanism. Some more "fettling" (as they say in the UK, may Oz?) and that eventually got sorted.

Now the BIG problem: the mechanism won't fit into the body.The decoder is too wide, wider than the mechanism, to fit past the window assembly on the carbody. Looking at the decoder, there are components and traces that are extremely close the the edges and do not want to attempt that modification. Had enough of this when installing decoders in the Intermountain F units a few months ago.

All this makes me wonder if the manufacturers (I mean the people that make the locomotives and the people that make the decoders) actually try installing decoders in their products even just for quality assurance purposes. And not during product acceptance, but during the manufacturing life-cycle. Seems to me there is some dimension creep in more than a few cases. I can appreciate that it may add additional cost to making locomotives, but I think they owe us to ensure product compatibility. When they offer locomotives with installed DCC, do they run into these problems?

In retrospect maybe I would have been better off installing hardwired decoders, but you would think the replacement boards should be a no-brainer. Doesn't seem to be a problem with Kato or Atlas. That's why I willing to pay more for a replacement board, but now I'm re-assessing that assumption.

BTW, never did get to work on my modules. Ended up drinking beer, eating pizza and watching war movies with my German Shepherd, Teddy.

[peteski]

You watched warm movies after fighting a major war yourself?  Couldn't get enough, could you? 

Unfortunately welcome to the real world.  Supposed plug-n-play decoders being wrong dimensions are not out of the norm in this hobby. I wish it didn't happen, but it does. Someone somewhere screws things up (and you would think that it would be simple and easy to make things right in the first place).    Usually the replacement decoder boards are too thin and they have to be shimmed (on many Atlas locos). Shimming is easier than trying to remove material.

AFAIK, Zamak (or some very similar alloy) has been used for all the split-frame mechanisms since the beginning.  Why do you think that these frames are not Zamak?

As for finding a tool to fit in the narrow slot, I have used a Dremel with a worn down cutoff wheel.  As you use cutoff wheels, they wear down and get smaller. Once they are about half of their original diameter (or smaller), I save them for special jobs.  The (front or back) face of a small diameter cutoff wheel can be used as a grinder in tight spots like the decoder slot. Just go easy and don't put too much pressure.  You can also use the edge as you go down into the slot.  For even tighter areas (like a corner of the slot) I have used a hobby knife with a blade with a broken tip to literally scrape off the soft white metal..

[ridinshotgun]

You aren't the only one.  I tried last week to put two digitrax board into some IM tunnel motors and encountered the same problem.  I got the slots opened up enough and the boards seated good but the motor tabs are way off and giving me problems.  Just had to set them off to the side till I have enough patience to deal with them.  Might even decide to go another route if I have to start soldering everything.

Anyone tried one of the TCS decoders and know if the tabs line up better.  I have a basket full of IM locos to do.

[C855B]

TCS went in my SD40T-2 without issue. I may have tinned the frame contact pads, but I do that with all decoders.

[ridinshotgun]

TCS went in my SD40T-2 without issue. I may have tinned the frame contact pads, but I do that with all decoders.

Hmmmmm.  Maybe I'll see if I can pick a TCS decoder this weekend in Altoona and try it before I commit.

[jagged ben]

At this point I'm well aware that an IM tunnel motor install involves the dremel and a fine point milling bit to widen the slots.  Tricky work.  If I widen them too much then I tin the tabs on the decoder until I have a good fit.  PITA, for sure.

It's Digitrax' fault.  Let's be clear about that.

[ridinshotgun]

At this point I'm well aware that an IM tunnel motor install involves the dremel and a fine point milling bit to widen the slots.  Tricky work.  If I widen them too much then I tin the tabs on the decoder until I have a good fit.  PITA, for sure.

It's Digitrax' fault.  Let's be clear about that.

I agree that digitrax is at fault.  I have put in a bunch of decoders board replacements, both digitrax and TCS, and never had a boards motor tab pads be so far off.

That said IM is at fault too for the tight board slots.  Everyone of mine look like IM took a press to the frame after they installed the factory boards.  In some instances it has even created deformed corners above the slots.  Not exactly a great way to ensure good fit and I haven't seen it done that way in other brand of locomotive.

[jdcolombo]

"Drop ins" are rarely that. Either the pickup tabs are too thin for reliable pickup, or the motor tabs are off or something.  The only true drop in is if the engine uses a standard plug, like Fox Valley.  Everything else should be called a "kludge-in". Better to just hard-wire and be done with it - particularly when you can get better performance from an ESU LokPilot or Zimo MX621.

John C.

[jagged ben]

"Drop ins" are rarely that. Either the pickup tabs are too thin for reliable pickup, or the motor tabs are off or something.  The only true drop in is if the engine uses a standard plug, like Fox Valley.  Everything else should be called a "kludge-in". Better to just hard-wire and be done with it - particularly when you can get better performance from an ESU LokPilot or Zimo MX621.

John C.

The DN163K1C, in my experience, meets the standard for the term 'drop-in'.   But, as an exception to the rule, this supports your point.

[Big Train]

Peteski,

I was thinking about using the Dremel cut-off wheel to widen the slot, but as seen in the photo, it still won't allow me to mill the slot completely to fit the decoder because some metal will still remain There isn't much material in this area and the possibility of grinding the tab off or weakening this area could happen.

The photo also shows where the tab was preyed open slightly with a slotted screwdriver. This section will accept the decoder board easily, but further toward the motor mount (where the lead holder is pointing) is the area that had to be widened.

I'm sure jeweller's or watchmakers might have the correct tools. Or even Micro-Mark. Might be worth checking out catalogs.

[peteski]

I see. Then like Jagged Ben mentioned, you could use a small milling bit (a dental bur) to remove the metal. You can get those in very small sizes.  Micro-Mark probably carries them too, but I get mine from Rio Grande.
Something like this would do the trick: https://www.riogrande.com/Product/LYNX-Square-Cross-Cut-Bur-25mm/348711



They have hundreds of different shapes and sizes of burs.

[Big Train]

The next time I'm at the dentist I might "borrow" a few off the tray while he's stepped out to chat-up his rather attractive assistant.......

Actually, I see MicroMark has a selection of burrs. I'm sure they will work as intended.