Want to Replace DCC Guts of HO Scale Atlas B30-7

[lyled1117]

TCS does a motherboatrd that fits this locomotive, used in my B23-7's. Use it with a 21 pin decoder of your choice

Lyle D

[davefoxx]

I'll have to use the AS-MB2-NC, because the plugs in my B30-7 do not match up with any of those motherboards.  So, I won't be getting off easy and will have to solder the connections.  I think I can handle this, though, although I may need some guidance on wiring, because this Atlas locomotive does not have color-coded wires to match the directions of the motherboard.

Here's the decoder that's been plucked from the B30-7.  I've now committed, because there were three wires that had to be cut to get the decoder out (visible at the right end of the decoder):



DFF

[davefoxx]

Here's some of the questions that I have:

1) What are the circular thingies on the motor near where the wires are soldered to the motor tabs?  Do I keep these?



2) Aren't LEDs sensitive to polarity.  How am I going to figure out which wire connects to which pad on the decoder to not burn the LED out?



3) Okay, maybe not a question, but I think I'll salvage that circuit board at the back (disconnecting all other components), so that I can keep the LED for the rear headlight.  Any obvious problems with this proposal?




DFF

[lyled1117]

I'll have to use the AS-MB2-NC, because the plugs in my B30-7 do not match up with any of those motherboards.  So, I won't be getting off easy and will have to solder the connections.  I think I can handle this, though, although I may need some guidance on wiring, because this Atlas locomotive does not have color-coded wires to match the directions of the motherboard.

DFF

You'll find it straight forward. One connector (two wires) are the motor leads, will go directly to the motor. You can apply a nine volt battery to the motor leads to see which is the plus lead (ORG) for forward travel. I seem to recall each truck also goes to its own two pin connector so those will be easily identified. Left side of truck and right side should be easily recognized. The speaker will be apparent too. If you use the original LEDs , you'll need to determine their polarity. Don't use the original resistors, QSI boards apply 5V rather than 12V to their LEDs. Make sense?

Lyle D

[davefoxx]

So, the initial shopping list is:

1) TCS AS-MB2-NC motherboard
2) ESU LokSound Select 73900 decoder

For now, I'm going to salvage the factory speakers and see how that works out.  I can always change them out later, if they don't meet my expectations.  I'll also reuse the LEDs for the front and rear headlights.

DFF

[davefoxx]

You'll find it straight forward. One connector (two wires) are the motor leads, will go directly to the motor. You can apply a nine volt battery to the motor leads to see which is the plus lead (ORG) for forward travel. I seem to recall each truck also goes to its own two pin connector so those will be easily identified. Left side of truck and right side should be easily recognized. The speaker will be apparent too. If you use the original LEDs , you'll need to determine their polarity. Don't use the original resistors, QSI boards apply 5V rather than 12V to their LEDs. Make sense?

Lyle D

I think this makes sense, and it isn't too difficult to trace the wires to determine what they are.  But, on the resistors attached to the QSI LEDs, do I just cut them out and not have to worry about 12-14V going to the LEDs?  I don't know how to determine their polarity.

Thanks,
DFF

[lyled1117]

I think this makes sense, and it isn't too difficult to trace the wires to determine what they are.  But, on the resistors attached to the QSI LEDs, do I just cut them out and not have to worry about 12-14V going to the LEDs?  I don't know how to determine their polarity.

Thanks,
DFF

You can leave the present resistors in place, but add additional resistance to get to a safe level for 12V. Use a resistor somewhere around 1k to 2K, you'll be fine. If you replace the resistor, same value. Once you have a resistor installed but before connecting it to the motherboard, you can use a 9 volt battery to determine the LED's polarity. Don't apply voltage to the LED without a resistor in place.

Also, I see you say "speakerS". If there are a pair present (and there should be because it's QSI) only wire to one of the speakers or wire them in parallel. QSI wires them in series for a 16 ohm load because an 8 ohm load overloads their amp. Loksound will do fine with 8 or 4 ohms. If you wire to only one of the speakers, it might be desirable to replace the other speaker with a 'plug' that fills the hole the speaker comes out of. It may not be a lot of volume but the 2nd speaker if unwired *might* diminish the sound generated by the 1st because it might move in response to the 1st speaker moving.  It might also work as a passive radiator and help the sound, but I don't know that. Stereo speaker cabinets sometimes use passive radiators to enhance their sound, but if that applies here I don't know.

You may also want/need to replace the speaker with one that can handle more power. The Loksound decoder can put out a lot more power than the original speaker is rated for. If you don't crank the volume, the original speaker may be just fine.

Lyle D

[davefoxx]

Thanks for your help, Lyle.  Sorry to be dense, but I'm not sure how to determine what resistor is on the LED leads for the QSI set up.  So, if I were to just remove them, what resistors would I use to protect the LEDs?  I figure this would be a cleaner install not to have so many resistors on the LED leads, plus, hopefully, I can use the same resistors on other projects.

I turn my sound down significantly, so I'll just give the factory speakers a shot and see how that goes.

DFF

[peteski]

The yellow "lollipop" disks at the motor leads are ceramic capacitors used to suppress radio frequency (RFI) noise generated by the motor's brushes arcing.  Usually installed in models being made for European market, due to the strict anti-radio interference regulations Leave them installed for now. Some decoders don't deal well with those, but I'm pretty sure ESU decoder (being European) can handle them.

If you want to replace the LED resistors, using 1000 ohm (1k ohm) resistors is a good starting value.  the LEDs will be safe with those. If too bright, you can replace them with higher values (like 1.5, 2.2, 3.3, 4.7k)

[davefoxx]

The yellow "lollipop" disks at the motor leads are ceramic capacitors used to suppress radio frequency (RFI) noise generated by the motor's brushes arcing.  Usually installed in models being made for European market, due to the strict anti-radio interference regulations Leave them installed for now. Some decoders don't deal well with those, but I'm pretty sure ESU decoder (being European) can handle them.

If you want to replace the LED resistors, using 1000 ohm (1k ohm) resistors is a good starting value.  the LEDs will be safe with those. If too bright, you can replace them with higher values (like 1.5, 2.2, 3.3, 4.7k)

@peteski,

Thanks for the information.  Will this work?

https://www.ebay.com/itm/25-x-1k-Ohm-Carbon-Film-Resistors-1-4-Watt-5-1K-Fast-USA-Shipping-/171314192156

Thanks,
DFF

[k27463]

@peteski,

Thanks for the information.  Will this work?

https://www.ebay.com/itm/25-x-1k-Ohm-Carbon-Film-Resistors-1-4-Watt-5-1K-Fast-USA-Shipping-/171314192156

Thanks,
DFF

Check the wiring diagram for that motherboard -- I believe the TCS motherboards typically include built in resistors for LEDs.  Some of the pads will have them, some won't.

[davefoxx]

Check the wiring diagram for that motherboard -- I believe the TCS motherboards typically include built in resistors for LEDs.  Some of the pads will have them, some won't.

@k27463,

You're right!  The AS-MB2-NC motherboard is for LED use ONLY.  According to the instructions, "All output functions have built-in, current limit resistors for LEDs."  Not only does that make this easier, but that's less parts that I have to worry about having on hand when I tackle the assembly.  I can freely yank all of the electronics out of the QSI decoder and just salvage the LEDs.  Nice.  I want to reuse the circuit boards that hold the front and rear headlights, because they put the LEDs in the proper location within the nose and long hood.



Boy do I appreciate the knowledge around here.  Thanks to everyone for your help.  I apologize for my ineptitude at what probably is basic electronics.  Thank you for your patience.

DFF

[davefoxx]

FYI, the TCS motherboard #AS-MB2-NC and ESU LokSound decoder #73900 were ordered last night from Streamlined Backshop.  I already have a tracking number.  Hopefully, despite the holiday, I'll have the parts in hand by this weekend.

Stay tuned,
DFF

[peteski]

@peteski,

Thanks for the information.  Will this work?

https://www.ebay.com/itm/25-x-1k-Ohm-Carbon-Film-Resistors-1-4-Watt-5-1K-Fast-USA-Shipping-/171314192156

Thanks,
DFF

Yes, that would have worked.
While the included resistors on various boards is a nice feature (and sufficient in most cases), it is also good to pick your own resistor value to be able to select our own LED brightness.

[jdcolombo]

Hi Dave.

Just so you'll know: my understanding is that the AS-MB2 board comes with a separate KA4 keep alive (that is, the keep alive is not on the board, but plugs into the board).  If you are planning on using the keep alive, the KA4's dimensions are 13.25mm square by 11.5mm thick.

One of the circuit boards that you're going to keep has some hefty-looking caps on it; I wonder if these are keep-alive caps, and if they could be used in place of the KA4?

John C.