Hi malaki
What you found is the construction manual for the JTM45 amplifier - that´s not the same as a JTM45/100 but shares some similarities with it. One could say the JTM45 is the grandfather of the JTM45/100 (and that is the grandfather of the JTM 100s and later 100W Super Lead amps).
Have a look here for A LOT of information on the topic:
http://forum.metroamp.com/viewtopic.php?f=7&t=25127" onclick="window.open(this.href);return false;
I myself don´t have any amp building experience yet - I´m still gathering information and parts for my first build (a 1969 Superlead). But that alone already took me 4 months yet.
Just as a general advice I want to tell you that the JTM45/100 is certainly not the easiest build to start with. It will take A LOT of time in the end and building amps seems to cost more than buying used working amps on ebay (or here on the forum from experienced builders) in the end. And there is George of course. So - my advice is: Only do it if you are willing to take the whole experience. And believe me - it will be an experience. Don´t do it if you think you can save some money by building your own amp. Have you thought about getting a used Marshall JH100 (Jimi Hendrix Reissue) amp - it´s basically a reissue of the JTM45/100 and I guess it could be fitted with a PTP board and generally be modded to be more true to vintage specs.
Cheers
YF