Bachmann 44 tonner - making it better

[reinhardtjh]

Can't wait to build a 65-tonner from the 44T and 70T models...

Yeah, I need a 65-tonner too.

 

[peteski]

Don't forget most of that junk on the top of the board is for RFI suppression to meet Euro appliance guidelines. Chokes and high-value caps don't miniaturize well.

That is not entirely accurate.  The RFI suppression is done using 2 very small caps and 2 chokes.  That is a standard suppression circuit.  Compared to its overall size, the RFI component do not take up a significant part of space in this decoder.  Funny thing is that Bachmann uses the same brand of microcontroller that is used by Digitrax.  It is just that they use larger versions of all the components.  Resistors, caps, transistors, diodes and even the microcontroller are in physically larger packages.  The overall component count (like you've mentioned) is also much higher.

This all goes against the goal of making the decoder as inexpensive as possible.  Larger components do not really cost less money than the smaller ones.  The large component count also probably makes the decoder overall more expensive to manufacture then the equivalent (but much better) Digitrax DZ125.  To be honest, I'm really surprised that the the Chinese didn't simply copy one of the much simpler (thus cheaper) decoders - like the DZ125.  Obviously, I do not have all the facts to figure out why Bachmann did what they did

So now you can see thru the cab?

Well, yes, I can now see through those way undersized windows.    If you look hard, you can also see the electronic components, but you do see the light coming from the windows in the opposite side.  But you can get the same effect, even with the original decoder. You just have to remove the black piece of plastic from the cab.  To do that you first have to remove the cab (which is quite a challenge).   In order to pop the cab off I ended up cutting off couple of the cab's mounting tabs which engage the walkway.

Nice work Peteski.  Any chance you'd be willing to create and sell some of those replacement boards preassembled?

Well, how much would you be willing to pay for this conversion (especially considering the low price of this model)? 

I suppose I could build half a dozen, but for that it would make sense for me to instead of hand-drawing, draw the boards on the computer and use the more complex photoetching method.  For even a larger quantity I would have to farm out the PC board manufacturing to one of the prototyping PC boards manufacturers.  That would get even more expensive.  Plus, I would have to allocate some of my hobby time to this.  That is the largest obstacle. I have to admit that doing even a small run doesn't look good at this point (unless I stop spending my hobby time on the online forums). 

Neat job on that PC board, Peteski.  I've been looking into that for other DCC conversions also but I don't have the stuff to make my own boards.  Yet.

Also like the PC board . I have MM etch stuff , 5 years old at least , some day maybe i'll read up and use it when I get an itch to etch but when is still sketchy .

Guys, it isn't all that difficult to etch your own hand-drawn circuit boards (like the one I used in this loco). No need for MM etching kit. All you need is some etching solution (I think Radio Shack still carries it), some blank PC board material, an old fashion inkwell drafting pen and some hobby paint, and a small container for the etching process.

Very nice work.   Did you use one of those ink pens to draw out your PC board?  I haven't done that since
the 1970s, but it sure is handy for small one-shot boards like this.   Looks very neat.

What do you use to polish the metal?  I really like the look of those contact surfaces.  That would be a great
thing to try on the undersides of some Kato diesels and other engines that depend on truck frames rubbing
on the split frame to make contact.

Thanks Max!
To polish the frame, I start of with a mill file (if needed), Then I move onto a 4-way emery board for fingernails (purchased in a beauty supply store)  I use Tropical Shine brand.

The final polishing is done using a Tob Brite polishing paste and a buffing wheel in a Dremel tool.


As for what I use to draw traces on the blank board, here is a short tutorial (which I originally posted on the A-board).
http://forum.atlasrr.com/forum/topic.asp?TOPIC_ID=64393&whichpage=2
A-board is now gone. 
I tried the photresist pens (like Sharpie) and I found that they don't give sufficient coverage (the ink in them is not solid enough so the etchant starts to attack copper areas which are supposed to be protected).

Also tried rub-on dry transfers. Those worked better but were pain in the a$$ to work with and sometimes they left behind waxy residue which acted as etchant resist.

If I want a very simple one-off printed circuit board I use a plain old gloss green Testors PLA enamel (thinned slightly with some Testors thinner) applied directly to the copper clad board using an old fashion inkwell drafting pen. Mom used to use these for technical drawings many years ago and now I found a new use for them. Why green paint? Because it had it handy and it shows up well on copper. Notice the price on the bottle cap - that gives an idea of how long I had that bottle!.  Here's a photo of what I use.



Here is a closeup of the inkwell drafting pen. I just dip it in the paint bottle then wipe the outside of the blades with a piece of paper towel. Then I adjust the screw for the line thickness I want (testing on a scrap piece of PC board. I then draw the traces/pads directly on the copper clad PC board.



I start by drawing the PC board in 1:1 scale on paper.  I then cut a piece of blank PC board to the size I need. I clean the copper cladding very well before drawing the traces and then don't touch it with my fingers (to prevent contamination of the copper layer). I use a slightly abrasive copper cleaner made for polishing kitchen pots. I then often outline the pads and traces on the bare copper using either a pencil or a sharp scriber (very, very lightly). Then, while wearing a rubber glove on the hand which is holding the board, or I hold it through a piece a paper I draw the pads and traces with the technical pen.



Next, when the paint is dry, I pour some etching solution into a shallow plastic container large enough for the board I'm etching.  I often use the clear plastic blisters cut from various packages. Blisters from items such as Micro-Trains trucks or couplers are perfect size for etching tiny PC boards.  I then float the PC board upside down on the surface of the enchant.  Since the fiberglass/epoxy board is translucent, I can easily tell when the etching process is complete.  Etching takes between 15 minutes and 1 hour (depending on the thickness of the copper cladding and the ambient temperature).  Finally I rinse the etched board, and clean up the paint using lacquer thinner.

Here is an example of couple of tiny circuit boards created using the method I described above. It'll be used to hold tiny SMD LEDs and resistors used for locomotive headlights. It makes it easier to mount the LED inside the loco body and it gives a good place to solder wires which will be routed to DCC decoder.



When I need a more complex circuit board or if I need more than one board, I use a more advanced method. I lay out the traces on my computer (using Corel Draw) and I print it out on a transparency using my Alps printer. Here is an example of such design.



For this method I take a well-cleaned copper-clad board and I coat it with a layer photo resist (from aerosol can).
Then I place the photomask I printed directly on the sensitized PC board. It then gets exposed to UV light and then it gets developed. I use positive-acting resist so the photoresist on all the non-exposed areas (where photmask was black) will remain on the copper and all exposed areas will be washed away exposing bare copper. Then I immerse the PC board in copper etchant which will etch away all the areas not covered by the photo resist. After copper is etched away I then have to remove the leftover photoresist and I end up with a nicely etched board.

I use Ferric Chloride for etching copper (Radio Shack carries it).
Photoresist is from Electrolube (British company) http://www.electrolube.com/products/maintenance-service-aids/188/29/ I don't know if they still distribute it in USA.
Standard copper-clad PC boards are 1/16" thick. That is bit too thick for me. I use much thinner boards. Like 0.032", 0.020" or even thinner. Those are harder to find (at surplus prices), but they often show up at electronic surplus websites like http://www.goldmine-elec.com/ or http://www.allelectronics.com/


There are several other methods for producing PC boards (like iron-on transfers) but I never got into those.  The bottom line is that for simple one-of PC boards hand-drawn artwork is quick and easy.

[dnhouston]

Well, how much would you be willing to pay for this conversion (especially considering the low price of this model)? 

Looking at the parts: DZ125, 2 LEDs, 2 resistors, board, shipping (to you), tax, etchant, etc. - I estimate a cost to you of around $35.  Assuming that the over-current protector would be my job to remove from the old board and solder to your board, I would be willing to pay $50 (+ shipping) for the replacement board.

I know the model does not cost much more than that, but given its role of yard switcher, it will be used a lot and good operations will be crucial.  I can replace the decoder myself for under $30 but it would be "sloppy".    To have a nice "drop-in" solution with upgraded lighting would be worth the extra price (at least to me)

And Heaven knows I'm not asking you to give up any of your online forum time!  We're all guilty of spending too much time on that 

[mmagliaro]

Peteski,
I follow.  Nice.  The inkwell pen... wow.   
Nice tip on just using Testor's enamel.  I have used the Sharpie type pens for this, and they work,
but like you said, you have to really work at it to keep traces from being eroded.

As for making small batches of PC boards (not hundreds, but maybe 20), I give a big thumbs up
top those iron-on kits.   I have used Press-n-Peel PnP Blue.   You draw your art on the computer, print
it out on a laser (can NOT be ink jet), or print it on paper and take it to a copy center where
they are friendly enough to put the sheet of PnP film in their hopper, and photocopy the art
onto the PnP sheet.   Then you just iron it onto the copper and etch like you do with your hand-draw boards.

It makes for really neat, fine work.  I was surprised at how good it preserves fine lines. 
I wouldn't do a motherboard with it ( heh! )  but for a small board with a bunch of discrete components,
or a few ICs, it works great.

[Cajonpassfan]

Nice and clean and elegant, I like it! Still, a lot of work.
One of the simplest things do improve this particular model is to add weight to improve electrical conductivity, operation and tractive effort. I slapped some tungsten weights on the bottom; there is room under the tank and the weight just clears the rails. Paint it black and call it a day...
                                                                                             
Otto K.

[SP-Wolf]

The coupler conversion is a fantastic idea. I'll be removing the ginormous McHenry's I had installed and going this route. As for the decoder-- I retrofitted in the Digitrax DZ123M0. (At about $28.00) Minimal effort-- great performance.

My 2 pennies,

Wolf

[Scottl]

I love this kind of resourcefulness.  When I last did circuit boards, I did them via an online service.  If you are making several, it is very cost effective, but this solution is perfect for a single board.

For those of us without a supply of 30 cent Testors ( ), I wonder if nail polish would work?

"Colossal Buffer"- I could see a clever header image in that.  Only men (modellers) use beauty supplies for trains!

[mmagliaro]

I love this kind of resourcefulness.  When I last did circuit boards, I did them via an online service.  If you are making several, it is very cost effective, but this solution is perfect for a single board.

For those of us without a supply of 30 cent Testors ( ), I wonder if nail polish would work?

"Colossal Buffer"- I could see a clever header image in that.  Only men (modellers) use beauty supplies for trains!

I got a kick out of that 30 cents price on the Testors cap.  I haven't seen that since I painted Aurora plastic
monster model kits in the early 70s.

[peteski]

I love this kind of resourcefulness.  When I last did circuit boards, I did them via an online service.  If you are making several, it is very cost effective, but this solution is perfect for a single board.

For those of us without a supply of 30 cent Testors ( ), I wonder if nail polish would work?

"Colossal Buffer"- I could see a clever header image in that.  Only men (modellers) use beauty supplies for trains!

Thanks Scott!  As far as nail polish goes, that is a "maybe".  I had to thin the gloss green Testors PLA enamel slightly to make it flow better.   Nail polish is even more viscous, so I imagine it would have to be thinned too. Plus, nail polish dries faster than Testors gloss enamels (has a more volatile solvent), so it might start skinning over while still in the pen. But it would sure be worth a try.  I do use thinned nail polishes for airbrushing bodies of model cars I build.

As far as your last statement goes (about only men), I suspect that Karin (and other female modeler TRW members) are way ahead of us men when it comes to creative modeling uses for beauty supplies. 

[peteski]

Looking at the parts: DZ125, 2 LEDs, 2 resistors, board, shipping (to you), tax, etchant, etc. - I estimate a cost to you of around $35.  Assuming that the over-current protector would be my job to remove from the old board and solder to your board, I would be willing to pay $50 (+ shipping) for the replacement board.

I know the model does not cost much more than that, but given its role of yard switcher, it will be used a lot and good operations will be crucial.  I can replace the decoder myself for under $30 but it would be "sloppy".    To have a nice "drop-in" solution with upgraded lighting would be worth the extra price (at least to me)

And Heaven knows I'm not asking you to give up any of your online forum time!  We're all guilty of spending too much time on that 

LOL!

Looks to me like you arrived at a fair price. I won't get rich, but I won't be losing money either.  If the other couple of people who expressed their interest in this conversion also get on board, I'll make a small batch of these boards.  But I can't really commit to a time frame.  And yes, you would have to unsolder the over-current protector from the Bachmann decoder and solder it to my adapter board.

[peteski]

Well, yes, I can now see through those way undersized windows.    If you look hard, you can also see the electronic components, but you do see the light coming from the windows in the opposite side.  But you can get the same effect, even with the original decoder. You just have to remove the black piece of plastic from the cab.  To do that you first have to remove the cab (which is quite a challenge).   In order to pop the cab off I ended up cutting off couple of the cab's mounting tabs which engage the walkway.

Looks like I had a senior moment (and I did this conversion only few weeks back).  I just took apart another 44 tonner, and now I see my mistake. 

The black plastic piece which covers the cab windows is attached to the decoder board. It comes out of the shell when the chassis (with the decoder) is pulled out of the shell.  That piece houses the over-current protector.  Still, it can be removed to allow some light to shine through the cab (but some of the view through the cab will be blocked by the over-current protector).

[towl1996]

I'd be interested in one and I'm in no hurry, so, if you're willing to do another.   

[central.vermont]

Pete,
I'd be interested in the etched board only. I can do the rest of it myself.

Jon

[u18b]

Pete,
Fantastic job.  I love your work.

I was studying what you did.

I wonder, if it is not possible to compress the components to the left.
In other words, move the decoder to the left away from the middle.  Then you could remove the "cover" you were frustrated about and just insert a black painted hunk of lead weight in the cab- with Kapton tape on the board under the weight of course.

This would significantly add to the weight of the loco I would think.

[peteski]

Pete,
Fantastic job.  I love your work.

I was studying what you did.

I wonder, if it is not possible to compress the components to the left.
In other words, move the decoder to the left away from the middle.  Then you could remove the "cover" you were frustrated about and just insert a black painted hunk of lead weight in the cab- with Kapton tape on the board under the weight of course.

This would significantly add to the weight of the loco I would think.

Thanks Ron!
Both hoods slope slightly towards the ends, so there is less clearance the farther you go away from the center. While designing the board I mounted a blank board on the chassis and then I pushed a decoder in under the hood until it jammed.  Then I backed it out slightly (to leave a tiny bit of clearance.  I already filed down the PC board mounting posts on the chassis to mount the PC board as close to the chassis as possible.  I will revisit this while making the 2nd batch of these boards, but I suspect that unless I use thinner decoder, I won't be able to fully move it under the hood.

I wasn't the one lamenting the black cab insert. I removed it in my conversion.  The question was whether it was removed to see the daylight through the cab (and it was removed). Like you said, it could be replaced by a weight. That might be a good idea, but that was not the question at the time.