Phil,
Except for azimuth, I do my head alignments by eye. This is much easier if you are replacing a head with all its "stock" mounting hardware and case, as the tape "wrap" and gap centering will be pre-determined. Wrap is the amount of angle (hence area) that the tape contacts the head as it is traveling across it and this area must be centered in the head gap. Alignment is also much easier if the headblock is removable - as is the case with the 1500.
As I just said, with a "stock" head and mounting the wrap angle is basically pre-determined and you then (only) have to set 3 other conditions; 1 - whether the tape is traveling parallel to the pole faces when looking in from the front (azimuth) 2 - whether the tape is traveling parallel to front of the case when looking in from the side and 3 - whether the tape travels over both pole pieces "equally" (the "height" adjustment)
Let's take 3 (height) first. Put the headblock face up on your bench and, "hold" (with two hands) a scrap piece of recording tape across the tape path. If you are aligning a 2 track head, the trick is to see whether the tape equally traverses both pole pieces and if not, adjust the screws that lift the head up or down to get that "equality". Problem of course is that the tape is opaque and you can't see through it - long time ago, someone used to make a solvent that could remove all the magnetic material and binding from a section of tape rendering it transparent. Absent that approach, in all heads there are what I will call "windows", where the manufacturer has opened up the case to expose the pole pieces; and if you are lucky, on a given head these windows may be wide enough (they're normally symmetrical for each pole) so you can just see the top and bottom of them even with the opaque tape covering most of the windows up. Do the best you can. It may be impossible to adjust many quarter-track heads if you can't see through the tape because their "windows" are just too narrow. To adjust 2, whether the tape is traveling parallel to the head when looking from the side; I hold the headblock sideways and view along the tape path "sighting" across the head to determine if its vertical surface looks parallel to the corresponding surfaces of the heads and/or tape guides on either side of it. If not, adjust the screw that "rocks" it front to back until it looks as parallel as possible. Azimuth can be approximated but is best set via a test tape and appropriate measuring equipment.
Of course another problem that must be mentioned here is that most heads have 3 adjusting screws and turning any ONE of them actually actually moves the head in TWO planes - so that making any one adjustment mentioned above actually involves jiggling two screws simultaneously and hopefully equally. Do this while chewing gum and whistling - simultaneously. As the new head wears, you'll begin to see the ware marks from the tape. Careful inspection of these marks can indicate whether your adjustments are correct - immediately readjust if not.
Regarding level setting - this is now of course determined by the outboard preamp and downstream electronics. I guess if the net level is enough to drive your system to an acceptable volume there is no issue - if not then there is. Finally, if the new head is of a different type than the original, it's frequency response may very well be different. Hopefully your reproduce electronics have compensating adjustments and you have the necessary test tape and monitoring equipment to perform them.
Good Luck
Charles
FORGOT - DEMAGNETIZE ANY newly installed head AND for that matter the ENTIRE TAPE PATH BEFORE playing any tape.
