Z-Test III Zenith Z-TAC Test Chip Mod
by G-Man of Group 42
Introduction
The Z-Test III test chip is one of the best test chips for Zenith
Z-TAC boxes using either the 221-165 or 221-288 processor. It
requires you to program a PAL or GAL with the
Z-Test III code and
to install the PAL into the Zenith Unit.
Installation
- Program a PAL or GAL with the Z-Test III code.
- Prepaire PAL or GAL by:
- Cut away or bend up pins 14,15,16,17, and 19.
- Solder pins 8,9 and 10 togeather.
- Solder pins 11 and 12 togeather.
- Solder wires to and bend up pins 1,2 and 18.
- Using a security #15 driver bit, open the Z-TAC box.
- Locate the 40 pin chip marked 221-288-xx or 221-165-xx.
- Locate and remove PROM chip. It is normally, but not always, marked
IC6663 on the circuit board. It is a 16 pin chip normally
in an 18 pin socket located near the 40 pin processor chip. In
some modles it may be covered with epoxy.
- Insert Ztest-III test chip in PROM socket. Be sure to note the
location of pin #1. (see diagram for more detail)
- Connect wire from pin #1 of Ztest-III and solder it to pin 10 of
a 221-165 processor or to pin 13 of a 221-288 processor.
- Connect wire from pin #2 of Ztest-III and solder it to pin 11 of
a 221-165 processor or to pin 10 of a 221-288 processor.
- Connect wire from pin #18 of Ztest-III and solder it to pin 12
of a 211-165 processor or to pin 12 of the 221-288 processor.
- Make sure that the Ztest-III pins 1,2,14,15,16,17,18, and 19 do
not go into PROM socket.
The modification whould now be done, plug the box in and select a
scrambled signal. If all the channels work properly, you are finished.
If you only get a picture on pay type channels, then short pins
4 and 5 on the 221-288 processor chip. if the pay type channels are
displaying inverted video or flashing, then find a jumper block near
the 40 pin processor. In older units, it is a black think with 7 holes
plugged into a 14 pin dip socket. In newer units the second jumper
normally corrects the inversion problem. In older units try jumpers
2,3 and 5. Also not that units with a 221-165 processor there is
no jumper block and you may need to adjust the zero carrier in order
to make the unit authorize and unscramble. Do not short pins
4 and 5 of a 221-165 processor.
On some of the st-1612 type units you may need to run a jumper between
pin 7 of IC12 to pin 12 on the 221-288, If this doesn't correct your
problems try running the jumper to pin 13 of the 221-288.
Hookup Diagram
