In the EU, it is important to differentiate between the statutory guarantee which results from the sales contract and is between the customer and whoever sold them the product (not necessarily the manufacturer) and any additional manufacturer’s warranty which applies on top of the statutory guarantee.
If something that you buy turns out to be faulty or doesn’t look or work as claimed by the seller, the seller is responsible for fixing this within the statutory (typically 2-year) period (the details are a little more complicated). The manufacturer, if different from the seller, has nothing to do with this – except that very often the manufacturer will repair or replace the product on behalf of the seller, but that is between the seller and the manufacturer. Many products come with additional manufacturer warranties that have longer terms and/or cover issues that the statutory warranty doesn’t address, but these are offered entirely at the manufacturer’s discretion.
The synth company is probably within its rights to refuse repairs under its manufacturer’s warranty (if any) to customers who have opened the case without authorisation. But this does not apply to the statutory guarantee which the seller of the device must extend to the customer. IOW, if you buy one of those synths new from your friendly music store here in Germany¹, then if that synth breaks down during the first two years after you bought it, chances are that the music store will need to sort this out (by repairing the device, replacing it, or refunding what you paid) at no charge to you. (Assuming that it didn’t break down because you opened the case and fooled around inside it with a soldering iron.) After those two years, it depends on whether the manufacturer provides a voluntary warranty and if so, whether its terms entitle you to a free repair.
- By way of example; Germany has a two-year statutory guarantee (the EU minimum).
