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Heljan 128 fries a decoder or two


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I used a digitrax 166 decoder on my new Heljan 128 DPU and the decoder burnt. The locomotive still runs fine on DC though. I tried with a Dapol Imperium and that too became unresponsive although there was no burning. Both decoders are not accessible on the programming track indicating that they have failed. 
 

Am I using decoders that are not suitable for this locomotive? What sort of current does this locomotive draw? In the picture the burnt hole is visible. 

3E4D06DD-75C6-4B1E-A782-C191F382AF35.jpeg

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I think your loco has a problem. It is, as many of us have been pleased to find, a mighty hunk of motive power, takes no prisoners and could probably pull walls down. I'm not sure which decoder is in mine, since it was bought s/h already chipped, but after a couple of years it is still working fine, and your purchase of this decoder with 1.5 amp capacity and 2 amp peak should have been more than adequate. I use mine to tow a track-cleaning wagon, so when it runs it generally is moving for 15 or 20 minutes to clean everywhere. 

 

On DC does the motor become hot? 

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I realise this does not help the OP but for the amount DCC decoders cost (or rather how much is charged) they should have output protection built in. In other words even if you have a short circuit at the output they should not fry themselves. This protection is available in many voltage regulators (e.g. 7805) that cost less than £1.  A DCC decoder is much more complex and sells in fewer numbers but cost 20-30x as much.  Perhaps the cheap decoders could not have this (you pays yer money an takes yer choice) but to hear that the pricier ones blow is disapointing.

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6 minutes ago, H2O said:

I realise this does not help the OP but for the amount DCC decoders cost (or rather how much is charged) they should have output protection built in. In other words even if you have a short circuit at the output they should not fry themselves. This protection is available in many voltage regulators (e.g. 7805) that cost less than £1.  A DCC decoder is much more complex and sells in fewer numbers but cost 20-30x as much.  Perhaps the cheap decoders could not have this (you pays yer money an takes yer choice) but to hear that the pricier ones blow is disapointing.

 

Quality decoders do have output protection - Lenz, Zimo, etc..     

But, US products don't typically fit such devices.  Gaugemaster DCC products are bought-in devices rebadged as Gaugemaster, some of their decoders are from Digitrax, and some are the common Chinese copy of an old TCS design - both US origins.  

 

Back at the loco, having blown two, I'd be (a) checking the current draw, and (b) putting a multi-meter over the PCB to check that tracks are not connecting "pickups" to "motor leads" when the decoder socket is empty.  

 

 

- Nigel

 

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I have tried to read the decoder and all is reset to zero. I tried to reprogram and that works. Then on the main track no response. Then back onto the programming track reading reports zero again. This means that the decoder resets itself when on the main track. 

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5 hours ago, Nigelcliffe said:

putting a multi-meter over the PCB to check that tracks are not connecting "pickups" to "motor leads" when the decoder socket is empty.  

I have had this problem on an Athearn loco. the track + wire was bridging to the motor + on the motherboard (these 2 connections are joined on the DCC blanking plug so this fault will only become apparent on DCC)

With the blanking plug installed the loco ran fine on DC, when I fitter a decoder it ran ok in one direction but the magic smoke was released in the other direction

Have you tried the decoders in a decoder tester or another loco

John

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Programming the decoder works okay. When it is read then all values are zero. Does this indicate a damaged decoder or bad contacts?

 

furthermore when resetting the CV 8 to 8 the controller says 

 

‘no decoder ACK pulse!’

 

does this mean that the decoder is RIP?

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6 minutes ago, Deborail said:

Programming the decoder works okay. When it is read then all values are zero. Does this indicate a damaged decoder or bad contacts?

 

furthermore when resetting the CV 8 to 8 the controller says 

 

‘no decoder ACK pulse!’

 

does this mean that the decoder is RIP?

 

Can't tell.   Could be anything, but does point to a possible decoder failure. 

 

BUT, if a loco destroys two decoders, it suggests a problem with the loco which should be investigated, as pointed out in previous posting.  It is possible to have a fault which destroys decoders yet gives correct running on DC.    

 

 

 

 

 

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