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Vintage IMAI.S.S. Power Supply Voltage Conversion

I've recently returned from Japan and have brought a loot with me. Whilst in Tokyo, there was the annual Antiques Jamboree at Odaiba and I happened across a box of HO KTM brass that I could not refuse.

This set included a lot of track, two powered locomotives, rolling stock and a power supply. Thanks to the age of the kit, the power supply was 110v only. Preliminary testing in my Tokyo hotel proved that everything was in fantastic working order. I assume this box has been in someone's cupboard for quite a while.

Don't plug anything rated at 110v into Australian sockets

You don't want to try this at home. Our powerpoints are more than double the voltage of that in Japan... I wonder if this explains why we have a ground line. Either way, any Japanese equipment that is not dual-voltage will bake if you plug it in. This beautiful old transformer would never handle it's new home.

I had the option of chaining in a power converter, but this would have been tedious. In fact, this is my first 110-only product and I would've needed to purchase a step-down transformer. Instead I chose to pull the thing apart and replace the transformer.

What were you expecting? Integrated Circuits?

I opened up the power supply and felt that I'd opened a treasure chest. I could pick out the potentiometer for the throttle, the switch for the direction and the transformer. The final component needed to be a bridge rectifier to convert the AC to DC, but it ... didn't look like one at all.

Following the wires, it seemed that there were 5 contacts on the device I assumed was the rectifier. A little googling informed me that this is a vintage metal rectifier with selenium insulation acting as the diodes. Very cool actually.

Purchasing a replacement transformer

Jaycar is my local electronics store of choice (if not the last available store in Australian cities) and perusing their site came up with a valid substitute.

There were quite a few to choose from, actually. As the amperage went up, so did the weight. I assume the copper coil mass dictates how much current the transformer can deal with.

Transformer transplant

This all went quite swimmingly. The existing wiring was labelled for safety-sake.

It turns out that the 110v input wires were hardly twisted and taped together. I would hope that this wasn't an original factory job... but as far as I know this is a Japanese brand and this should have been the original factory plug. Quite interesting... let alone dangerous.

Once the 110v transformer was out, the new transformer was soldered and then bolted in.

It just fit. I mean.. a few millimeters more and we would've had to determine if Jaycar does returns.

The 240v feeder was passed in and the wires were heatshrinked, the rest were soldered in place as per the previous construction.

Plugging it in...

With breath held, I plugged the transformer into the power board. It worked. The light lit dimly and no smoke came out.

I rigged up a quick test track from the box of treasure purchased in Japan and tested the KTM ED100 that also came with it. After a little wheel and track cleaning the locomotive started bolting along.

Success! This transformer is solid... although has zero short-circuit protection! Smoke started to appear during a motor short.. but I couldn't determine the source... I'll make bloody well sure in the future that shorts don't last too long.

The directional switch is momentary unless you force it to either extremity. This is a nice touch as you can set your speed and then pulse the direction as required.

After running my brass EF62, I found a screw left on the track... the downfall of brass locomotives is that they're bound to shake things loose eventually!

I was nothing short of ecstatic to have found this box at the antique fair in Tokyo.