Issue with Hornby TTS chip in Bachmann class 47

[08221]

Hi.

 

Today I put a Hornby class 47 TTS decoder into my Bachmann class 47 using an 8 to 21 pin adapter.

 

The loco ran fine for half an hour on my rolling road so I programmed up its 4 digit address. Then retested - all working fine.

 

I have just put the loco on my layout again All was as expected for about 20 minutes. Then the loco just stopped and the sound went off. Now it’s completely dead except the lights come on and off at one end - no sounds at all or sign of the loco moving.

 

Can someone advise me please what I have done wrong. When it was running OK, my Powercab was showing it was pulling about 0.3 amps. But now when I put in on the track it’s showing 2.4 amps.

 

Thanks in advance for any assistance- stay safe, well and happy.

[Paul80]

One thing often recommended when fitting TTS decoders into Bachmann Diesels is to insert a resister around 500 ohm to 1k ohm IIRC into the blue wire as Bachmann locos have more demanding lighting thst is known to overload the TTS decoders, not saying that is behind your problem but something to do with the replacement to be safe. 

 

I had one die in a Bachmann 66 because of it.

 

Paul

[RAF96]

TTS function outputs are not self protecting so it pays to restrict lighting loads to well below the 100mA limit.

In fact if you disconnect the blue wire temporarily you may find it has recovered, as the motor self protection may have kicked in and stopped it.

A decoder reset may also work.

TTS warranty even covers user mishandling, so as long as you have proof of purchase within the year they will replace it.

[letterspider]

Apart from when they arrive faulty - I have had no problem with Class 08, 20, 37 or 66 TTS decoders but I have noticed that they can get very warm when running.

The 47 decoders can be used in Vitrains  with no problem but in Heljan locos they fry almost instantly and I have given up on giving them sound. I don't have a Bachmann 47 at the moment ...

Edited August 7, 2020 by letterspider

[RAF96]

You should always carry out a motor stall load check in DC config then choose a decoder with a suitable rating rather than use the plug n see if it will hack it method.

 

Added to that you should calculate the lighting load and using a suitable value resistor restrict the function current to within decoder limits.

[08221]

Thank to everyone who responded to my query.

 

I have just got round to doing a decoder reset (CV 8 to 8). The decoder is now working correctly and sound is all working too.

 

But the lights are stuck on in one direction - F0 has no impact and they stay on even if the loco is running in the other direction (in which case, both headlights are on).

 

If anyone knows a way of just getting the lights turned permanently off (I'm not bothered about them to be honest!), it will save me having to return the decoder.

 

Thank you again, stay safe, well and happy