Fried a DCC Decoder… wondering what else I’ve done…

[markwilson]

I’ve just made a very stupid mistake and I’m trying to work out how bad it is.

 

1. I thought I’d drop a DCC decoder into my Heljan 03.
2. I put it back together and there was no response from the loco when I tried to programme it.
3. I tried on both the programming track and on main. No luck.
4. I opened it up and saw I had misaligned the 21 pins - only 1 row connected.
5. I lifted the decoder off, connected properly and witnessed a puff of smoke. Arghh. Track power was still on.

 

So that Zimo MX634D is now fried. Annoying but we live and learn.

 

My concern is that I’ve blown up the main PCB too? I put the blanking plate back on and tried to run it in a DC track but no luck. That could be the controller though as it’s an old Gaugemaster Model D - possibly not enough grunt for a Heljan O gauge loco?

 

I will test on the club layout this week, but is there another way for me to see how badly I’ve damaged the loco, please?

[Ray H]

Have you put the blanking plate back on the right way up?

[markwilson]

I think so, but that’s worth a look I guess! Will report back in a while. Thanks for the suggestion @Ray H!

Edited October 1, 2023 by markwilson

[markwilson]

1 hour ago, Ray H said:

Have you put the blanking plate back on the right way up?

Thanks for the suggestion. I just checked and it is now (it wasn’t 🤦🏻‍♂️).

 

Really needed to be pushed right down but working now. Thank you @Ray H!

Edited October 1, 2023 by markwilson
A bit more fettling made it work. Edited correspondingly…

[Nigelcliffe]

And when the decoder went "pfffttt"   did you put the decoder in the right way up, as well as the right way round ?   

 

21-pin is a complete mess as a standard,  there are so many ways to get it wrong !

[Kaput]

Did the loco actually work on DC before you started this adventure? The part about only having an old controller that might not be up to running it on DC makes me ask the question.

 

If all else fails try applying DC power directly to the motor to rule out any PCB issues.

[Nigelcliffe]

40 minutes ago, Kaput said:

 

If all else fails try applying DC power directly to the motor to rule out any PCB issues.

 

ONLY do this without a decoder fitted (when it is a good test).    Applying DC to the motor with a decoder fitted can end in smoke from a decoder...

 

 

[markwilson]

13 hours ago, Kaput said:

Did the loco actually work on DC before you started this adventure? The part about only having an old controller that might not be up to running it on DC makes me ask the question.

 

If all else fails try applying DC power directly to the motor to rule out any PCB issues.

Yes, it was an eBay purchase and I had run it in on the club test track. I just didn’t have an “o gauge” DC controller at home.

 

It’s working on DC with my controller now though, once I’d refitted the blanking plate correctly. I’m normally very diligent but yesterday was clearly not my day and I think I just panicked after seeing smoke!

Edited October 2, 2023 by markwilson
Typo

[markwilson]

12 hours ago, Nigelcliffe said:

 

ONLY do this without a decoder fitted (when it is a good test).    Applying DC to the motor with a decoder fitted can end in smoke from a decoder...

Thanks for the advice!

[markwilson]

14 hours ago, Nigelcliffe said:

And when the decoder went "pfffttt"   did you put the decoder in the right way up, as well as the right way round ?   

 

21-pin is a complete mess as a standard,  there are so many ways to get it wrong !

I can’t be sure now because I whipped it off again so quickly. Interestingly, after I confirmed that it will still run on DC (phew), I tried the decoder again and had some successful running for a while. But, later in the day, it just didn’t want to play at all, so I have clearly done some DCC damage and have put it back to DC only until I can free up another suitable decoder.

[Nigelcliffe]

2 minutes ago, markwilson said:

I can’t be sure now because I whipped it off again so quickly. Interestingly, after I confirmed that it will still run on DC (phew), I tried the decoder again and had some successful running for a while. But, later in the day, it just didn’t want to play at all, so I have clearly done some DCC damage and have put it back to DC only until I can free up another suitable decoder.

 

It is possible of course,  but if the decoder worked for a while, after the earlier problems, then it was working..   Decoders which are working don't usually just fail a bit later.   

 

 

But, back at the first posting.....   how did you manage to connect only 1-row of pins, when the more common arrangement of a 21pin on the Loco PCB has the pins going through the rear face of the decoder PCB - upper picture of below is the more common arrangement, and matches what I've found of the online Heljan instructions for your loco:  

 

 

 

 

- Nigel

 

 

 

[WIMorrison]

Might be worth looking at this thread

 

Hard Reset of Zimo Decoder - DCC Help & Questions - RMweb

[markwilson]

53 minutes ago, Nigelcliffe said:

[…] how did you manage to connect only 1-row of pins, when the more common arrangement of a 21pin on the Loco PCB has the pins going through the rear face of the decoder PCB […]

Ah, I see where you’re going @Nigelcliffe. 

 

Looking at the decoder now, the only way I could have misaligned it is if it were upside down. The header side has 22 “holes” but the PCB side has 21, as expected, to prevent numpties like me from misalignment.

[RAF96]

The decoder be fitted in either compact or rotated configuration according the the NMRA standard, I.E. per the Heljan illustration earlier.