Hi everyone. I have a Victron Energy Easysolar MPPT 100/50 that blew due to a Gekko getting inside it and shorting the AC input. It blew a track off the board and seems to have blown the PCB transformer connected to it. My question is this. The transformer is primary 300V and secondary 16.4V. I can only get primary 230V & secondary 15V. Can I replace it with this spare? Does the extra 1.4V matter too much?

What is the function of the transformer? 

Victron are well supported so I would phone their main support centre and speak to their repairs dept. They might have a scrap PCB with a good transformer.

It might work, but is a really bad idea.  Rather get the correct part. Victron will probably supply it, or you should be able to get it on Aliexpress (I am pretty sure Wahhing has a store there).

If you really must use an alternate part, then there are lots of things to consider.  Firstly, the primary to secondary ratio is the important parameter, so 300:16.4 would equate to 230:12.6 - so you would be looking at a 12.6V transformer. Next are he reactive losses, which are likely to scale with the square of the differences, so you need a 70% higher VA rating.

Then you get the things you can't do anything about:

1) insulation resistance (relates to max voltage, and usually has a fat margin on - but can you be sure it will hold up, and how long).

2) absolute inductance - which won't match at all unless you use exactly the same part (although it is often not critical, unless the part is used in a resonant or flyback configuration).

It is important to note that 230V transformers are much cheaper and much more available than 300V, so there is probably a very specific reason (likely one of the two above) why Victron chose a 300V part.

Thank you for the advice. I will try to get one directly from Victron.

That's the power supply board you've got there. You should be able to order a replacement PSU board and swap it in, have a chat with your nearest repair center (not sure where they are exactly).