Is there a reason you refer to "the God of the Old Testament" rather than "Yahweh" or "Jehovah"?
I would like to be as accurate as possible. Both Yahweh and Jehovah are guesses at the Divine Name. (God of the Old Testament = YHWH)
If "the God of the Old Testament" is part of the Trinity, which part is he? Is he the Father, Son or Holy Spirit?
OK, this is where the words become confusing. To the JW mind, God=Jehovah=Father. From a Trinitarian point of view, "God" is three Persons. Moreover, there have always been the Father, the Son and the Holy Spirit.
Now, from this point, I would need someone with more knowledge of the doctrine to continue. Perhaps someone can help us out.
Specifically, would it be accurate to say that YHWH is all three Persons of the Trinity? Anyone?