Decoder Missing ??? [How can I tell without removing the body]

[Chrissaf]

If you have a multi-meter. Set it to measure resistance.

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Measure the resistance across the wheel pickups.

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If there is no decoder fitted, then you should be measuring the DC resistance of the motor coils. Can't give you an exact value to expect, but somewhere between 10 and 50 ohms seems a reasonable estimate.

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If a decoder is fitted, then the meter will be trying to measure the resistance across the bridge rectifier of the decoder. This will be a lot higher than 50 ohms, in fact several thousand ohms. I have just measured the value across a spare Hornby R8249 decoder I have lying around and measured 30,000 ohms one way and 31,000 ohms the other.

[Chrissaf]

Hi Everbody, I recently purchased a loco from e bay, described as  with (DCC fitted), tand set it up in my loco list OKhe problem is that I can't program it? 

I tried it on the track replacing my loco set at 0003, and it does'nt work.

I then placed it on my program track ,Iafter setting it up in my loco list as 0009. 

When I try to progrm it (Hornby Mallard- R2339), I put 0009 into the address on CV1,

press the sigma key as it is a long address . press "write to the loco decoder", the value in CV! goes back to 009 ?   and goes green. That is one issue but the other seperate from this is that  I tried to look at the cvs in the loco which was on the programming track, I pressed"  the read CVs button" , it started ok and then , came up with decoder unodtainable? 

I suspect that there is no decoder fitted , how can I be sure without removing the body which on a "brand new" loco would invalidate any complaint. The box sats "DCC ready" not DCC fitted.

I would welcome your advice, I have sent the seller a message asking him about this but so far I have not received a reply, Thanks - Barry. 

 

 

 

 

 

 

 

 

[Baz48]

Thanks Chris, I have just done this the resistence flucuates between 20-50 ohms , therefore, there is no decoder fitted?. Thanks for this!

However could I ask for your advice please, this afternoon I rigged up an analogue controller to my test track and tried the loco on this.

It ran forward and reverse , but with a jerky motion, and there was a regular clunk every revolution of the wheels.I checked the obvious , con rods etc. but there was nothing fouling the motion. I then gently pressed down on the loco and the wheels stopped rotating but I could still hear the motor running and the regular clunk clunk continued as though the drive beween the motor and wheels was slipping? 

Any ideas please? .  This is supposed to be a brand new motor. Many thanks, Barry. 

[Chrissaf]

Your observations seem to indicate that one of the drive gears (probably a plastic or nylon one) has split and become slightly distorted, hence the click. A split would also make the gear slip on its shaft, hence the motor continuing when the wheels are forcibly stopped.

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The 20 - 50 ohms certainly indicates no decoder present.

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For the benefit of other readers. This is an example of why I keep going on about the need to have a multi-meter in one's tool kit. It can be so incredibly useful to diagnose and prove things.

[Baz48]

Thanks Chris, May i again ask for your advice, this loco was sold to me on e bay as "DCC fitted"" and "Brand New" and never run and had been stored in its box all the time..

I have contacted the seller and he tells me that it was one of his fathers locos , never run etc.and he himself knows nothing about model railways.

I think that Ihave 2 options to consider:

1/ ask for a full refund.- Which I am entitled to as the item was not  "as described" .

2/ I feel that the seller is genuine and has made a honest mistake. -  I do like the loco as it is very detailed and does appear to be brand new due to the packaging etc all being as if it has never been disturbed. - I could therefore ask for a partial discount to cover the cost of a Hornby decoder , say £16 for the decoder and £14 for fitting ( and I could fit this myself) , say a £30 discount on the auction price I paid of £102, resulting in me paying £72 , however then there is this motor transmission problem which may be simple to repair, (I feel that I could carry out this repair and would probably enjoy it!). I might have to pay say £10 for parts and I could ask for this ammount to be retunded, This would result in a £40 refund, meaning that I have paid £62 - do you think this would be fair to the seller?                                                                                                                       I would welcome your comments / suggestions as I want to be fair to the seller.- Many thanks , Barry.

[Chrissaf]

Well that seems fair enough to me, but you are in a bit of a catch 22 situation.

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I think it would be prudent to know before hand whether the loco could be repaired. Getting 'spare parts' even for a new or recent model can be more difficult than obtaining spare parts for much older locomotives in this 'throw away' society. The only way to know would be to take the loco apart and investigate, identify what parts were needed and then investigate their availability.

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This is where the 'catch 22' bit is. You have already stated that you don't want to take the loco apart and risk your return options, but you need to take the loco apart to minimise your risks of keeping it.

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Let us assume for a moment that the loco is indeed in brand new condition and never been run out of the box. But your new information now says that the loco originated from a deceased?? father and had been in storage. Now it may be that the father found the loco was faulty when he got it and didn't do anything about it at the time and just put it into storage to forget about. On the other-hand, if it was originally supplied in a working condition but has just gone faulty whilst in storage then for that to happen, the loco must have been in storage for an extremely long time. If we assume a loft, then that would be years of heat related expansion and contraction affecting the plastics. Hence why maybe something in the drive mechanism has split or failed.

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Keeping the loco and trying to repair it has risks. Only you can say whether the discount you negotiate is worth those risks. The risks could be mitigated only by taking the loco apart to investigate, but equally the risks could be exacerbated by taking the loco apart and either breaking it irreparably or not being able to put it back together again. Only you know your own capabilities ... it has to be your choice.

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[Baz48]

Thanks Chris, I asked for a refund and the seller agreed, I then removed the loco body and tried the loco on the programming track connected to an analogue controller , I could then see the jerky action close up, I stripped the motor assembly and removed the gear set , I could not see any damage , I reassembled and tried it again , this time I  applied a bit of pressure expecting the wheels to continue to rotate , they did not .I could then see that the motor was rotating , the large gear was rotating but the small gear ( on the same shaft), was not rotating , when I released the loco it ran as before. I stripped the motor etc down again and inspected closley the first gear set, , I found that the small gear was slipping on the shaft when only very slight pressure was applied..

I identified the correct gear set from the hornby website (X8849/21)  - 21 indicates the number of teeth on the small gear., I then ordered a new gear set from Peters Spares for £3.79, fitted this and the loco ran smoothly in both directions in analogue mode, I then purchased  a R8249 decoder from  an e bay auction site, for £10.50, I fitted this and refitted the body,  I programmed the loco on the test track to ID 009 and it now runs Ok, It pulls 4 illumninated Pullmans with ease from a crawl to full speed.- May I point out to others not to be aftaid of trying to do your own repairs, just be careful, do a drawing will help, and save all (tiny ) screws safely and note which screw goes where! - The most tricky operation in this case was refitting the body having fitted the decoder, this took a lot of patience and care.

Many Thanks Chris, Best Regards to All , Barry.

[Chrissaf]

Always nice to hear a happy ending.