How do I test a decoder?

[Johnboy99]

Hi , how do you test a Hattons 8 pin decoder as I don't know if that is my fault

thanks

[2e0dtoeric]

What happened?

There is no instant way of testing ANY decoder, if it doesn't appear to work.

Start by eliminating other possibilities - ie does any other loco work?

Have you selected the correct loco code? (new decoders are always set to 03)

If they all do, except this one, has a component failed? (smoke, etc).

Is it plugged in properly (all pins in, right way around, etc)

Have any wires come off in the loco?

Has the loco mechanism jammed (foreign body, something bent, etc)

Will the loco run on dc power (9v PP3 battery)

You CAN purchase a decoder tester, there are a couple on the market, but unless you want to fit a lot of decoders to loco's, it is hardly worth the expense. Your local shop or club might have one.

[Chrissaf]

There is a "Make your own decoder tester" article in this months edition (June 2018)  of BRM Magazine. I can't scan and post it, else that will breach copyright.

.

Note that there is a technical error in the magazine article instructions. I emailed the 'Articles Editor - Howard Smith' about it and got a reply saying that the error was acknowledged by them and will be dealt with at the earliest opportunity. I presume a correction will be printed in a forthcoming magazine edition. The error stated that the longest LED lead was negative, where in fact the longest lead is positive. Thus the tester would not work if following the article instructions as written. Personally, I think I could have built something better than that in the magazine, but the published design is functional and cheap. At the very least I would substitute the power resistor the article author uses with a small 12v electric motor.

[Johnboy99]

Thanks I have sorted it,

i was fitting a decoder and lights to a lima g w railcar and have spent almost 3 days trying to get the loco to run! 

What I had forgot to do was snip the little white resistor off when I did this away she went lights as well.

[Fishmanoz]

Little white resistor, presumably with coloured bands presumable. But where was this offending component?

[2e0dtoeric]

I'm assuming he meant capacitor - located across the pick-up wipers, where it would block the DCC data?

If it was across the brushes on the motor, it would make no difference, as there's no data present there to corrupt.

[Johnboy99]

Yes capacitor it was I thought it was called resistor me not up on these things yet,

thanks all.