The short answer is yes you

The short answer is yes you should be able to build a controller from scratch. If you want to. I'm not sure that you will save any money though.

You would need to be reasonably competent at building and writing code or script . It might take you several months , it might take a couple of weeks. If it were a stepper driven table , it probably wouldn't take all that much and theres probable already open source software to do what your asking using a desktop as the head.

Unfortunenately the turntable you have is a DC motor driven table and you probably have to come up with something from scratch.

You might take a look at https://www.pololu.com they supply a lot of controls ,motors,gearboxes for robotics . I would not recommend using any of the cheap Ebay/AliEx electronics , the documentation is for lack of a better word ...crap at best at worst nonexistent. pololu has good documentation and support and they list distributors in  Melbourne and Perth.

The simplest would be to use a pair  DPDT momentary ON-ON switches and control the motor manually . One switch for slow and one for fast .

Seems easiest...

To just scrap the DC motor and replace it with a stepper and an Arduino for control.... there are sketches already out there for this application so the code shouldn't be a problem at all. A number of folks have already done exactly that, too.
 

Options

Dear Philby,

As far as driving _direct_ from your NCE system, you could always grab a simple DCC Motor-only decoder and drive the motor direct... although you would then be reverting to Indexing via Mk1 Eyeball...

Alternatively, you could replace the existing motor with a stepper motor, and follow the excellent "Arduino Turntable Indexer" thread by "Pelsea" of this forum...

https://model-railroad-hobbyist.com/node/28501/?page=3/#comment-272281

Additional threads of interest/relevance can be found via the "Search" box at top right of this page.

EG

- https://forum.mrhmag.com/post/turntable-arduino-and-stepper-based-12208035

-  https://forum.mrhmag.com/post/control-the-world-with-arduino-12205507

-  https://forum.mrhmag.com/post/arduino-controlled-turntable-indexer-12207863

There are a number of Aussie modellers here onlist,
you may be able to find someone near to you who can help directly?

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Turntable fix

Thanks to everyone who replied sadly my technical abilities are very limited and don’t think I am up to fixing the problem of the missing controller I might have to spend the $500 and buy a new one the turntable is essential to the running of my layout.

cheers from Queensland Australia.

The only other suggestion

The only other suggestion that I have is purchasing a used turntable and using the controller from that. I think Hattons in UK has a couple and one was "bargain priced " at around 300 AUD.

As I said ealier It would not cost that much or be that difficult to convert to "manual" push button control but you wouldn't have indexing  .

Turntable Indexer

Hi,

I do not like promoting products on here but for the situation you are calling out, these might be the solution.  I personally like the arduino solution but if you are not into that, Just google search model railroad turntable indexers, and I found a couple of companies that make them for all manufacturers or scratchbuilt turntables. 

Check them out and maybe one will solve your problem.

Are you looking for the blue box?

We removed the blue box from our turntable and converted to manual control. The indexing worked OK most of the time but sometimes moved out of alignment and often needed reprogramming after a layout short. Also, people didn't find the ability to operate the turntable from the throttle to be particularly useful.

The manual operation uses a low voltage supply, on/off switch and a reversing switch. Much better!

Anyway we might still have the blue box. Not sure if it works or not. I think it came up with an error message and that is why we converted.

Bagal

Blue box

Sadly the control box I lost was white in colour and the blue one won’t do the job according to walthers thanks anyway.