Ok, so I got hold of the reverberator yesterday.
My friend will try to read the program from the eprom.
I should have the program for the reverberator somewhere this week.
We would also try to write the programs ourselves on the eproms.
So are there any specific instructions for the reading and the writing proces, i.e. the format in which the data should be stored or written?
For the piggybacking of the ic, the link does not work anymore.
The best description I could find on the internet is
http://members.optusnet.com.au/tonymy01/magnavox/indexbod.html
Does anyone of you have a more specific description for the 27C256 chips? Which pin needs to be connected to the switch? If I look at this picture:

It should be pin 20. Which resistor value should be used for the bridge between Vcc and ce? Also 27K, like in the website I just quoted?
For R38, can I use a "normal sized" resistor or do I need to use these smaller resistors as used for the rest of the board?
Digi2t, I inspected the photos of your modulator mod and is R38 on the other side of the board, because I don't see it.
Also for the Output mod, with the green wire you solder 2 legs to the casing of the pot. Is this to ground it?
Hehe, I have too many questions...
I'll keep you guys updated on the progress!