I found a nice looking K-Line S-2 that seemed like it would be a fun addition to my fleet of all postwar steam engines. I dropped it on the track as soon as I received it, and as expected, it was an absolute rocket with the voltage from my Lionel RW transformer. I had anticipated this and had already bookmarked a video on how to wire up the motors in series instead of parallel. Just snip the yellow wires and splice them together.
However, when I removed the shell I was surprised that it wasn’t the circuit board that I expected to from photos and videos. What this engine has is just a single IC chip with a 1000uF capacitor soldered to it. It’s attached from the positive terminal to the on/off switch and a brown wire comes off from there. Looks like a dab of hot glue attached it to the frame at one point and that has come loose. The wiring colors are all different as well – brown and red for the motors instead of the typical blue and yellow.
The model is a K-2311 Chicago & North Western S-2 and I’m not finding much online about it. The legacy K-Line website doesn’t seem to have it in their catalogs.
So some questions – is this just another version of the K-Line S-2 circuit board, or has somebody swapped out the control board? Is this going to work properly with a legacy controller like the RW? The heat shrink and cable ties on the wiring all seem factory quality, but this single chip sure seems a bit minimalist for a controller. (IC is labeled KBL005 7645 AC)
Second, it seems adapting the wires to series would still be OK. Following the wires from the motors and looking at the splices, I believe the red wires correspond to blue and brown wires correspond to yellow. Looking at the splices instead of blue/blue/yellow and brown/blue/yellow, I have a red/red/brown and brown/red/brown, with one brown going to the switch and one to the motor. I believe I would need to splice brown and brown?
Thanks for any wisdom you can share!
NOT an IC chip.
The reverse unit has been removed and replaced with a simple 4-6 amp Full Wave Bridge Rectifier and a DPDT switch for direction control. The capacitor is just a filter cap to smooth out the rectified DC.
You can use an aftermarket reverse unit if you want, but they are NOT cheap anymore since Lionel ran out of stock of their 103 type units no longer in production.
Thanks – I was worried that something like that might be the case. Not much of a switcher without reverse.
Will running in series still work? It’s insanely fast at this point – is that even worse due to this modification?
The series wiring will work perfectly.
Later production K-Line diesels actually had an extra DPDT switch on the bottom in addition to the reverse lockout switch to select series or parallel operation. You can do the same.
I would be curious what sort of voltage the motors are seeing if the big capacitor is on the full wave bridge as it looks to me.
When you have a simple full wave rectifier(w/o capacitor) the DC voltage will be about the same as the RMS AC voltage supplied, less voltage drop from the diodes. If for example, this is 18V RMS AC, assuming no drop from the diodes, you would see the DC peak voltage is around 22V even though the RMS voltage would be lower. If fed from a full sine wave source, you would see a nice pattern going up to this peak voltage and down to zero volts 120 times per second.
When a capacitor is added, it will tend to charge up during the voltage rise and stay there until enough power is pulled out to drop it to zero. If the capacitor is large enough(relative to the load) you may see little to no “ripple” in voltage. That means that the motor is effectively getting peak voltage, not RMS. That could explain why it is so fast(although often these can motor powered locos are pretty darn fast out of the gate).
The circuit is probably a little more complicated than that thanks to the motor’s inductance, but I’m rusty enough on that math to not attempt it.
I’d also be curious how something like this would handle a newer Lionel transformer or a unit like a Powermaster/TPC. Most of these always supply the peak voltage that the(iron core) transformer is ouputting, and vary the RMS voltage to the track by basically only using part of the sine wave(called “chopped” sine wave). At low voltages they tend to look like a shark fin, where high voltages tend to look a little more like a distorted sine wave. With a set-up like this engine, I’d still expect some variation since the power supply’s time at 0V is longer, but a big enough capacitor could still end up giving peak voltage most of the time. That would give almost no voltage regulation.
If it were mine, I’d put a scope on the motors and see what the power coming to them looks like. Putting the motors in series would let it run slower, but if it’s still too fast for your liking removing the cap(or maybe installing a smaller one) might slow it down.
Thanks for the input. I decided this was not the project for me. The vendor was great about taking it back for a full refund when I explained the situation, so thanks for knowledge shared!
