Faulty class 43 decoder

[Hipwell]

Hi guys.

I recently purchased a twin pack of class 43 decoders for my old hst which has been fitted with a cd motor. The loco ran perfectly on analogue.

So, today I made a start at hard wiring the chip into the dummy unit to start. After fitting I fired up rail master to find that I was getting directional lighting and no sound which I thought was odd.

So I went into loco settings in RailMaster and did a read CVs, and it came back with really random numbers, such as 0 on acceleration and deceleration which I know default to 15.

So I did a CV8 reset, and this did not work at all, and now I cannot read any CVS.

I tried to manually program all the CVS as per the defaults in the manual, which appears to work ok, but then when you try to read all CVS it just errors.

Back on the running track, directional lighting works, but no sound.

The other one works perfectly fine.

Are Hornby customer support just going to laugh at me due to chopping the 8 pin plug off to hard wire it in? I feel like I've probably just thrown £60 down the drain.

[96RAF]

It is not clear from your post if it is the dummy car decoder at fault or the motor car decoder. If the dummy then it may be RM cannot read back sensible Cv values as there is no motor load. You should just be able to write any new values. Is RM picking up the decoder as a TTS or simply as an R8249 decoder. If the later then use CV7 to pull down the correct one.

Hornby will not laugh at you, but will likely reject a warranty claim as they cannot test and prove the state of the decoder without a plug. You can however give them a call, on the premise that some of their installation guides show hard wiring of decoders by cutting the plug off.

Hard wiring a decoder is as just as much work as soldering in a DCC socket so I cannot see why folk resort to it unless the loco is particularly tight on space. The early and railroad HSTs have plenty of room for a socket.

[Hipwell]

Hi raf thanks for the response.

It's the dummy unit decoder which I'm having the issues with. The other one in the drive unit works fine.

It fails to read all CVS so Its not really picking it up as anything. So I read the CVS of the working decoder and replicated all the settings and wrote them to the dodgy decoder but still I'm only getting directional lighting and no sounds.

That's an interesting point you make about not been able to read the CV due to it not having a motor load, I will swap this decoder into the drove unit and see if the issue persists.

Hornby manual even suggested hard wiring is not and issue and I didn't have any sockets to hand so decided to hard wire :(

[96RAF]

Back to basics.

It could of course be a duff speaker.

F1 is switched on?

Although a reset should set master volume to mid point, check write that value to it just to be sure. Value zero would set the volume to Off.

Normally one could set volume levels on the main but RM does not support PoM.

To avoid swapping the decoders over simply wire a low ohm resistor across the motor wires - say 100 ohm, but just for the programming. If you leave it connected when you throttle up you will cook it and likely melt something in the loco.

[Hipwell]

Yeh F1 is definitely turned on, but just nothing happens. But when I turn the lights on (f0) the lights come on, and if I change the direction the lights change colour as expected

I think I could do with checking this chip on the motor end to see if I get any drive or still just lighting?

When I try a CV8 reset that also fails.

I have also tried just changing the volume as you say by writing a value of 4 to the sound CVS.

The fact that the lights are working, would this suggest the decoder is not dead?

[Ard Lochan]

This may be of help, I have half a dozen class 43`s with the factory fitted decoder socket and have had a problem with a couple of them where programming the dummy has been a problem, Either will not program or program properly wether due to the lack of weight or motor i dont know, They would also not respond to cv 8. I found that programming the dummy TTS decoder in the power car then fitting it to the dummy worked fine. It is also worth investing £30.00 on a decoder tester with which you can test and programm a chip before fitting thus saving a lot of hassle, Regards, Ard

[Hipwell]

Thankyou Ard. This is giving me some hope that the decoder might not be fried.

However, it's not giving me much of an explanation as to why I'm getting no sound.

I'll wire in the 100ohm resistor or motor tonight after work, try a CV8 reset and then see what happens!

Fingers crossed

[ColinB]

The one in the dummy has not got a motor load so reading CVs will be an issue. If you had done what 96RAF and myself do and wired in sockets you could swap between dummy and powered ends. I have a couple of TTS decoders that have failed with no sound so it is not so unusual. Next time test the decoder before you chop off the connector. In this case though there is plenty of space to wire a socket and you can get some really cheap ones off EBay if you don't want to pay Hornby prices, although I must admit their latest version is really good.

[Hipwell]

Thanks Colin.

I'll see how I get on tonight and contact Hornby if not, the issue is if the decoder is faulty it's going to be a pain because the class 43 decoders only come as a twin pack and I only need the one.

Having said that, it's not the end of the world only having sound at one end, the train is only 2 coaches long so I'm not too bothered.

When you say faulty sound, has it been due to a faulty decoder, or faulty speaker? If it's the latter that's not such a big deal as I could just replace the faulty speaker

[ColinB]

In my case the first thing I do if there are any issues is replace the speaker. no a couple of them have just failed.

[Hipwell]

Well quick update.

So I did the 100ohm resistor trick and can now program and read the CVS os that's a good start, but there was still no sound.

RailMaster was picking it up as an 8249 4 function and not a TTS, so I changed that in the drop down and made sure the volume settings were all on 4, still no sound.

So I desoldered the speaker from the chip, and checked it with a voltmeter. Completely open circuit on the speaker.

So, fingers crossed it will be a case of a new speaker and problem will be solved

[96RAF]

Good progress Hipwell.

[Hipwell]

All sorted 2 quid speaker off Amazon which happened to be identical to the one which came with the decoder!!

Thankyou all.

[Fishmanoz]

Good to see Hipwell. But if you have more problems, you might consider that many users replace the Hornby speaker with better quality (some do it routinely from new) which might include sugar cube or iPhone speakers, and get improved sound too. There are lots of posts about this.