Modification list for the final XL2
===================================

+15 and -15 need to be reversed on OP177Gs
  -lift pins 4 and 7 of U138 and U140
  -connect pin 4 to pad of pin 7, and pin 7 to pad of pin 4
 
Connect pin 9 of U10 via a 1k resistor to GND

Add 0.1uF capacitor between TP155 and GND (???)

REF-02C needs to be grounded at U139 pin 4.  Connect pin 4 to
   side of R171 physically closest to U139

Connect TP112 to TP120 to enable 1/n counter (with n=8)

--------------------

new mods are as follows: [July 15, 1997]

for data bus:

* lift U95 pins 12, 13.  connect pads together.
* lift U141 pin 8.  Connect pin to pin 13, U95.  Connect pint 12, U95 to U141
  pad 8.   

for DTACK:
* lift U119 pin 4.  Connect pin to U141 pin 9. lift U119 pin 12, connect pin
  to VCC.

--------------------
HV Mods [ Aug 5, 1997 ]
------

For interlock control:

 - replace R17 with 100 ohm resistor (was 1.5 kohm)
 - add diode on top of R127; orientation: arrow toward VCC

For HV control:

 - jumper TP111, TP136 to ground (sets 0 to 10 V programming voltage)
 - jumper TP128 with TP 130; jumper TP146 with TP147
	(this sets common to ground)

New HV control mods (D.M. 12/20/97)

 - Replace 5.1 KOhm R1 with a 75 Ohm and a 470pF in parallel (piggybacked)
 - Replace 5.1 KOhm R2 with a 200 Ohm but rotate the 200 Ohm 90 degrees and
   solder 1 end to the pad that goes to the EC connector and the free end
   should be soldered to a wire that goes to TP 121.
 
Disable SNO_RESET (XL2 reset) of HV supply enable (RGV Jan 2/98):

 - On U110, lift both pins 1 and 13, tie to U58, pin2.  This is the
   prom clock, and is used to reset the register on power-up.

Reduce blocking resistance on HVLOAD line (D.M. Jan 19/98):

 - Replace R19 with 200 Ohms.

Modification list for the XL2 for use with Bed-of-Nails
=======================================================

[see xl2-bed-of-nails.modlist in this directory]