How To Tell Locked And Unlocked Print Head?

Epson print heads are some of the most popular across the printing industry, they perform well and have been relatively cheap to get hold of. The DX7 was Epson’s replacement for the DX5, and it has been just as popular with printers all over the world.
Locked Printhead: For a long time, this worked well, with the second hand market for Epson DX7 printheads meaning affordable and reliable printheads were easily available.However, in 2014 they altered the DX7 printheads and introduced a secure algorithm that prevented these new DX7 heads from working properly when removed from its printer. When fitted as a used printhead, the results vary, but can include poor printing performance with missing or additional lines ruining the print, or even a failure to print anything at all.
In practice, that means that Epson printheads that removed from their machines no longer work, trying to do so results in either a small print or errors that ruin the print completely. However, the lock was eventually reverse engineered, and a memory card is available that overwrites the secure algorithm and makes these heads functional again.Unfortunately, Epson did not give up, and produced a second lock in newer heads that again restricted heads and made them unusable as used items. This lock has not been overcome, and so we now have a situation of having locked and unlocked heads on the market.
How to tell the difference?
Of course, with both locked and unlocked on the market, if you want to use Epson DX7 printheads for large format use, then you need an unlocked head, and you need to be able to tell the difference between the two.There is a simple way to make sure you are not buying a locked head, and that is through the serial number of the board. This is an 8-digit number, but it is the first three that are important. The first two numbers are the year of production, the third is the month, so for instance a serial number starting 135, would be manufactured in May 2013. What you are looking for is a serial number that starts with 144 or higher, as this means it was produced in April 2014 or later. Any head with that serial number are the later second locked heads that cannot be unlocked at present. 
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