Best Of The TP56/TP70 Kitbash thread N scale

[keeper]

As promised, here is the back of the cab...

[keeper]

@dcutting, what are those moulds for on the front and rear pilot?

[peteski]

I was going to say is that those are places for mounting the uncoupling levers, but looking at Ron's model (several pages earlier), those are wrong spots for those. He just left the dimples as-is and mounted the levers higher.

[tehachapifan]

My guess would be mounting holes for, say, BLMA MU hoses?

[keeper]

My guess would be mounting holes for, say, BLMA MU hoses?

Maybe, but pictures show only one MU hose...

[keeper]

Calling all electrical wizards... @peteski etc. ...

I found this Kato circuit board and was wondering if I could use it in a way for the lights.
The width would be perfect. It has to be shortened though...

A cut here and there, blue, white and yellow wire.... 



Thomas 

[u18b]

Calling all electrical wizards... @peteski etc. ...

I found this Kato circuit board and was wondering if I could use it in a way for the lights.
The width would be perfect. It has to be shortened though...

A cut here and there, blue, white and yellow wire.... 



Thomas 

Keeper,
I edited your photo.

All you really have to do is unsolder the resistor.
Then solder it back as shown.
Then trim the board.

The front board goes over the motor area.  The rear board mounts in the roof.
The red wires go to the motor poles.
The blue wires jumper to the LED board in the cab.  I would use magnet wire- it is easier to hide behind the center post of the front windshield.

Make SURE the blue wires are soldered correctly or you will burn out an LED.

Also, if the light up backwards at first, just reverse the red wires.
HINT- the way the Kato board is laid out, the front of the loco is top the LEFT.

So the left rail solders to the bottom of the board.
The right rail solders to the top rail.
Should run perfectly in analog.

We know this because you are using it EXACTLY like Kato designed it.  All we did was move the resistor.

By the way, when you MOUNT the boards, they will probably face oppositely.
That is... the motor board will mount as show with top up.

But the cab board may be mounted in the roof and mounted upsidedown.

That's fine, the wires will twist.
Just make sure you wire it as shown on the work bench will all facing up.

[peteski]

Thomas, you mentioned blue, white and yellow wires.  Are you going to be use the board for DC or DCC operation?

If you use DCC, there will be more modifications than  what Ron showed.  Also, will you be able to squeeze both the light board and the decoder in the shell?  Ron ended installing a very small LED on a small custom-made circuit board sitting over the decoder. Also, the rear LED will have to be in the top of the cab (not at the same level as the front headlight).

[u18b]

Good catch Pete... Thanks.

Oops.

Yes, let's be clear.

Are you using a decoder?

What I have drawn is for analog.

But the extra changes are not hard if using DCC.   One main difference may be the resistor. 

[peteski]

Good catch Pete... Thanks.

Oops.

Yes, let's be clear.

Are you using a decoder?

What I have drawn is for analog.

But the extra changes are not hard if using DCC.   One main difference may be the resistor.

Um, the LEDs are wired together in reverse-parallel. They will need to be separated.

[u18b]

But if the board is cut, then it's not an issue.

The cutting will separate them.

(assuming the board is cut   )

[up1950s]

Maybe the holes are for those Europeein buffers .

[u18b]

I dug up one of these boards from my stash.

Did some testing.

I'll post a DCC version that should work.

But you will need another resistor.

[u18b]

OK.  Here is the mod for DCC.

Here is a stock board.




Now use a soldering iron and remove the brown capacitor.  Scrape all the traces around there so there are no solder bridges.

Then unsolder the resistor.  Be careful so you don't damage it.  Heat one side, then quickly the other, then back and you should be able to slide it off with the iron.

Then cut two new spots in the traces as shown.  Make sure all copper is gone.

Cut the whole board as shown.   The long part goes from the motor to the nose, the small square part goes in the cab roof.




You need another resistor- say from another Kato board.

Now, solder the resistors over the gaps as shown.

Solder the decoder wires as shown.

Last, solder the jumper magnet wires.   I bought some green and red which helps with polarity. 
In this case, RED corresponds to the positive BLUE decoder wire.
The green corresponds to the negative YELLOW wire.



It should work.

[peteski]

The 560 ohm resistors might result in overly bright headlights. Kato uses those values assuming that most operators running DC will not run their models at full throttle.
But in DCC, the internal DC voltage will always be fairly high.

For example if the internal DC voltage (blue wire) is 11V and LED drops 3V across its terminals then 8/560=0.014A (or 14mA). I usually run my headlights at less than 10mA. But electrically 14mA should be ok. Those LEDs are fairly large SMD LEDs so their maximum recommended current is probably 15 or 20mA.   Smaller SMD LEDs like 0603 or 0402 are designed for 10 or 5 mA operation.