No, it is usually not possible to change the tuner.
There is a small (very small) chance that a factory service center could swap out the tuner module, but it would cost you as much as buying a complete new recorder with the newer tuner. Panasonic made some significant internal changes between the analog and digital models, so the likelihood your EH55 could support a newer digital tuner module is slim to none (the module depends on supporting firmware and hardware missing from your EH55).
You may need to compromise with an external DVB-T tuner box such as this:
Similar boxes are used by many North American members here to keep older recorders like the EH55 useful with digital broadcasts. Note the external tuner connects via your EH55 SCART or line inputs, so you will probably not be able to use the Guide+ integrated EPG system in the EH55 (unless you can find an external tuner that supports it). If you live in a country with large electronics dealers, you might consider a newer Panasonic with built-in DVB-T: this would be easier to use for timer recording, but would cost more and be missing some nicer features of your EH55 (the current digital-tuner Panasonics are not as luxurious as the older analog models).Edited by CitiBear - 6/27/12 at 8:37am