Juan, I just took another look inside the amp. According to what you say about the date codes on potentiometers, these date to 1968. I found two different part numbers on the pots; 1-505-305 6845; and B-302-304 6847.Would that mean this amp was built in 1970? The transistors have 2 different part numbers as well; 2N5133, and 2N4250. I can remember the numbers on the transistors, because I had so much trouble finding replacements. I'll probably have even more trouble finding a replacement volume pot for the old beast. It's the channel 1 volume, I use channel 2.