DCC decoder overheating

[Ollie0033]

I have read many of the posts on this subject but still have problems reconciling the reasons given against my particular problem.

I have successfully converted some 40ish locos to DCC - some hardwired but mosly with a prewired harness.

The engine I am having problem with is a Hornby A3 tender driven loco - Blink Bonny - nice loco!! Cleaned it all up tested it in DC and ran alot better than before (bought second hand). I had to decide how to proceed due to lack of room in the tender. In the end I decided to hard wire the decoder - not a difficult operation - tested the space available and everything seemed to be "on-track". One I had attached the decoder tested the engine and nothing - my first failure!!

I tried a different decoder - same issue - no movement - I had the decoder in my fingers at the time and noticed it was overheating.

I then tried other DCC engines on the line - no problen all ran well so no track short circuit.

I then put a harness in place - tried another decoder and no luck - no movement and overheating.. I then put in a blanking plate and ran in DC and all ran well. So I know the wires were all in correct order. There were no trapped wires since I had not put back the tender body. So I am completey lost - I have another 6 A3/A1's to convert and now reluctant to proceed. 

Can anybody suggest what the issue might be??? - I am sure it is some type of short-circuit but do not know where to start. Bye the way, I tried the decoders that failed on this loco on other locos and they ran okay - except for Gaugemaster and I am giving up on them - they don't run on anything well but thats another story.

[Rog RJ]

I suggest you do a stall current test (on dc) to find out what current the motor takes when it is stalled.  Then select a decoder that is able to handle at least that current.

[Howbi]

Ollie..........what DCC controller are you using..........also, have you removed the original capacitor from the motor?

[WilliamDavid]

What decoder did you fit? The Hornby R8249 is a 0.5 amp. I have fitted Hatton's 1.1 amp on my tender drive locos

[Ollie0033]

 First I removed the capacitor as instructed in several other forums and this did no good. Second I was using the hatton 1.1 amp decoder and this overheated.

I tried another A3 and had the same problem so in reading more it would seem to be an issue of current for a Ringfield 3 pole motor - having said that i have converted 20+ of these without problem - its just in the tender driven motor I have the issue.

After Rog had confirmed my suspicions on current that I diecided to go for something bigger. So, I then took out a sapphire I had saved for a X04 motor and tried this and low and behold it worked. Not very good at slow speeds - it was bumping around but at medium speed it settled down and ran smoothly. I have read about changing some CV settings but thats for another day. One other issue I have researhed is that several modellers say the Bachmann 36-553 would also do the trick - has anybody any experience?

[WilliamDavid]

In have modified a few Hornby tender drive locos

Flying Scotsman A1

Manna A3

Everton B17

King Henry VII

They all work fine with the Hattons 1.1A

I had trouble with one using a 0.5A decoder, but was advised on this forum to fit the Hattons.

I think it is normal for decoders to get hot.

The obvious.

You must make sure that the pickups are not connected to the motor inputs.

In some Ringfields the screw holding one terminal in place goes into the body, causing a short. This must be prevented.

[Fishmanoz]

Interesting the Sapphire works, nominally 1 Amp and the Hatton's doesn't at 1.1.  I'd be wary though given it is taking this much current when running, I'd still be doing a stall current test as Rog suggested to make sure you aren't going to blow it if you run against buffers some time.  I'd also suggest maybe the magnets are weak in your Ringfields to be using that much current.

 

Don't know anything about the 36-553 except it's spec says 750mA so I suggest not.  It does have CV54 and 55 back EMF adjustments for low speed running though if having problems with a loco needing less current.

[Pete172]

I have used the Bachmann 36-553 with XO4 motors, they do indeed work very well ..

[Ollie0033]

Just to finish off this forum if anybody is interested - I did a stall current test an found the tenders to be about 1.1 which is a little high - but before going and buying bachmann decoders to test i though I would give it one last go with a Hornby R8249 which I had nor tried - interestingly the spec for these is 0.5 amps - much lower than the hatton and the saphirre- but - they work!!!

With these decoders I found that there was no bumping or stalling they worked from slow speeds up to high speeds without any issues. So I have now recouped 7 from other hornby dcc ready engines and replaced these with hattons and they work fine (except for one class 50 super detail model that would only work with a lenz decoder yet this decoder would not work on the tender driven engines - weird!!!

I have seen many bad reviews of the hornby decoder but I now understand a little more about the diversity of engines and it goes to show there is no guarantee of success - you have to be prepared to experimentof. So all remains is to convert the other engines and fingers crossed I do not find any other anomolies.