Etherwave Plus pitch field growing...

"No, I don't have a plastic hex tool, but found this at another TW post here. Is this the one?"  - escapedpuma

I'd maybe get the kit just to improve the odds of getting the right one: http://www.landmelectronics.com/product.cfm/28653/

"Also I found this video about L5 and L6 tuning process..is it trustworthy?"

Others can comment, and I use a different technique with a scope, but it maybe seems like a good place to start.  In the video he states that the parasitic capacitance of the enclosure top is due to hidden metal screws, which is probably not true - the wood itself is somewhat conductive and this likely imparts most of the parasitic capacitance.  A little ungrounded metal here and there won't have much effect.

Hey, I 'm the guy that lives in Athens too.

I haven 't really played around with tuning the Etherwave Standard, but Bob Moog 's original article on the design should help you tune it:
https://www.cs.nmsu.edu/~rth/EMTheremin.pdf
If ESD got your main oscillator, then you will need to replace the transistor with a new one of the same type. Ideally, you 'd replace both transistors of the pitch side. You could find two with near identical behaviour, by checking them with a multimeter and making sure that they have similar hfe values. They are really cheap, so you can get, like, 10 of them and test them.

I don 't know much about the quality of the circuit board. If you are unsure about your soldering skills, get a friend to do the repair. It should be just a 5' job. Tuning it properly will be more challenging. Thierry is the expert here, so consider contacting him directly. He might even guide you through skype so that you can tune it.

Εύχομαι καλή τύχη! Αυτή τη στιγμή διαβάζω για την εξεταστική του Φυσικού οπότε δεν έχω πολλή χρόνο, αλλά θα μπορούσαμε να επικοινωνήσουμε. Θα ήθελα να δω από κοντά και να παίξω με ένα etherwave.

JohnnyWho, thanks for your information...Please check your PM