How do you know when a decoder has blown?

[aleopardstail]

Thanks for the clarity aleopardstail.
I thought it would be like re-flashing an EPROM although, as you say, you'd still need the code and suitable programmer.
Thanks
End2end

most of these chips support "ICSP", basically a serial connection designed to be used when the chip is "in circuit". sometimes its a plug & socket, the 3x2 one on the Arduino boards for example, on boards this size its usually five or so exposed copper pads. it goes into a housing, a lid is shut and pins contact those pads (note you couldn't do this inside a loco). that will provide power, ground, a two wire serial interface and a reset connection. the pins will be put into a specific state as it powers up and it goes into programming mode - data is loaded then the reset triggered. depending on the code and the chip it can also be verified by reading it back.

some of the programmers are simple, e.g. you can use an arduino to programme some of them, others need their own programmers - which is why I don't play with PIC stuff here, sodding expensive

real killer though is needing the code to flash it with, invariably kept reasonably well guided. indeed some of these chips in the programmer can have a fuse blown which disables the programming port to stop people reading it back

[centenary]

Could just get an ESU tester at about £40, that way you would find out if it was blown or not!

[End2end]

One wonders if the decoder can be sent back to the manufacturer explaining the problem and get them to check / re-flash the decoder or possible even replace it?
Thanks
End2end

[aleopardstail]

One wonders if the decoder can be sent back to the manufacturer explaining the problem and get them to check / re-flash the decoder or possible even replace it?
Thanks
End2end

some of them will, though I'd imagine its cheaper to just replace it

[Bigmet]

One wonders if the decoder can be sent back to the manufacturer explaining the problem and get them to check / re-flash the decoder or possible even replace it?

Depends on the brand. Why do I use Lenz and Zimo? Because there's a product warranty: Lenz had a ten year warranty when I started out in DCC, clearly a confidence building exercise to support uptake of the DCC system. Over the twenty three years since first starting with DCC, two such returns have been necessary: Lenz, there was a problem with some gold decoders all the time ago mentioned above, couple of years ago a Zimo decoder. Returned and replaced very quickly in both cases. That's over 200 or thereabouts decoder purchases, distrubuted 50/50 my own, the balance installations for friends.

[centenary]

One wonders if the decoder can be sent back to the manufacturer explaining the problem and get them to check / re-flash the decoder or possible even replace it?

Depends on the brand. Why do I use Lenz and Zimo? Because there's a product warranty: Lenz had a ten year warranty when I started out in DCC, clearly a confidence building exercise to support uptake of the DCC system. Over the twenty three years since first starting with DCC, two such returns have been necessary: Lenz, there was a problem with some gold decoders all the time ago mentioned above, couple of years ago a Zimo decoder. Returned and replaced very quickly in both cases. That's over 200 or thereabouts decoder purchases, distrubuted 50/50 my own, the balance installations for friends.

A product warranty only protects against manufacturing defects. If my decoder had blown, turns out it hadnt and, was due to User misuse, it's unlikely the manufacturer would honour the warranty.

I know of at least one 3rd party supplier, Richard at Roads & Rails who tends to replace decoders where User error has caused an issue although he's not bound to do so.

As per my OP, without a tester from such as ESU, I guess the only way the User can tell is by swapping out the decoder with another and seeing if the loco works. If it does, try the 'blown' decoder in another loco and if it still doesnt work, bingo!

[Bigmet]

...A product warranty only protects against manufacturing defects. If my decoder had blown, turns out it hadnt and, was due to User misuse, it's unlikely the manufacturer would honour the warranty...

Although I have never knowingly damaged a decoder by misuse, the question never arose with the returns I described. I reported that the decoders had ceased to function, and was told to return to vendor, and replacements were supplied. In the specific case of the Zimo decoder the replacement arrived following day first class post, whereas the return was still in my local post box - assuming the 'next collection' tab was correct in showing the previous day collection had not yet occured...

On a more general note concerning DCC loco decoders, I have been impressed by the durability of what are low cost consumer electronics, as judged by the high uptake of DCC systems for layout operation, and a relatively small proportion of decoder failure reports.

Especially considering:
inevitable handling by owners with no training, that do not earth strap themselves when installing, and may easily apply pressure to the circuit board when installing the decoder into confined spaces;

connection to RTR mechanisms which may be dubiously wired, with motor characteristics which can be 'wayward';

frequent evidence of no use of a programme track facility to verify a good installation;

power supply via a layout which may contain inputs other than solely that from an NMRA conforming DCC system.