Re: Tech needed on TZ

Well, it sounds like you basically found a "checklist" of "parts to replace"
but did you do any diagnosing to try and determine the actual cause of the
problem? Too many times I see people just start "shotgun replacing" parts
without doing any testing or finding out what's really going on- what is
working where, and what isn't- and it's usually just a waste of time and
parts- not to mention often unnecessary work/damage to the boards from doing
the "replacing"- and yet the problem still continues.

Chips like LM339s and ULN2083s (or any "chip" for that matter) are parts
that honestly really rarely fail, relatively speaking. It's much more
common to find problems with connectors and other causes that will produce
problems before something like a solid state chip will, so I tend to suspect
them last of all. They're definitely not fun to replace, either, so if you
can put off the work of replacing one by looking at other more likely causes
first, definitely take that approach.

A lot of times I've seen people attempt their own repairs and have ended up
causing more problems due to sloppy work or by doing something wrong
(knowingly or unknowingly), and not only does it cause further
head-scratching, but a lot of times if you get frustrated and finally turn
the board over to a qualified repair shop, they won't touch it because it's
had previous work done on it. So sometimes it's better left alone and left
to the professionals. Either that, or take a step-by-step approach with
proper troubleshooting and isolation of the problem to properly identify
parts that are truly bad, and do a good quality job of replacing those parts
so you don't do further damage to the board.

The first thing I would do on a problem like this is determine if the
problem is located on the MPU board (board problem) or if it's something
that's failed under the playfield (wiring/physical problem).

But even before that, I would check to see if I had 12v power coming off the
power/driver board, since, if I understand you right, it just so happens
that all (?) the optos are on that column 8. If the 12v power is absent
(blown fuse, etc.) then that will make the optos not work, and that could be
the cause of the problem you're seeing. Check for blown 12v fuse, cracks in
the solder joints around the 12v fuse holder (Ive run into this on a few
occasions on these boards) and make sure 12v is getting off the board and to
the opto driver boards and optos under the playfield.

If 12v is okay, then do a test on the MPU board to see if the switch
rows/columns are working there, with the playfield disconnected. Put the
game in switch test and remove the 5 switch connectors at the bottom of the
MPU board. Using your game schematic manual as a guide, and a clip-on
(alligator clips) test lead with a diode, manually activate the switches via
the connector pins at the bottom of the board by connecting the appropriate
pins there (with the diode in correct orientation). Typically you connect
one end of the test lead to a column pin (column 1, 2, or 8 in this case)
and the other end of the test lead to the diode's cathode (banded) end.
Then touch the other diode end (non-banded "anode" end) to the row pins one
by one- row 1, row 2, etc. The game's display should show the appropriate
switch number when you do this (have a friend help hold the display panel
aside so you can see it while you're doing the testing on the bottom of the
MPU board).

Test each switch in the #8 column this way. If they respond/register/work
this way (by showing up on the display as you connect them) then your MPU
board is fine, and you have a physical fault under the playfield (or again,
12v power problem with the optos- or ground problem- don't rule that out- I
once had a Dirty Harry game that had a bad/open ground from the opto boards
so no optos would work).

If you don't get any response from the #8 column switches when manually
testing with the jumper/test lead, then you've got a problem on the MPU
board- usually it's that U20 chip (ULN2083A) but there are several other
components in the circuitry that can fail, too. At that point you'd need to
use something like a logic probe or oscilloscope to go through the circuitry
and determine what is working and what isn't, to narrow in on the actual bad
component.

If MPU board is okay, then proceed to the playfield- check all switches on
that column for any faults (broken wires, shorts, and again proper 12v and
ground to/from the opto driver board(s).

But this should at least get you narrowed in on the portion of the game
where the fault truly lies, and may help save you a lot of time, work, and
money, too.

Good luck!

Ray J.
--
Action Pinball & Amusement, LLC
Salt Lake City, Utah USA
Web: www.actionpinball.com

We're serious about pinball. Anything else is just for fun!



"Bryan" wrote:
I purchased this machine with the existing problem and wondered if someone
could point me in the right direction. My Tz was showing a switch matrix
problem in column 8. Which is a several optics and the lock switch. I
check
for shorts and have all was good. After pulling out clays resource and
talking with Lloyd. I thought I was narrowing down on the problem. The
guide showed me to replace lm339s on the optics board and also replaced
the
chip at v20 postion. I installed the boards and continue to have the same
problem. The error has been erased from the main cpu because of the
installation of the new socket and chip. The switches in that row are
still
not working where do I go next. I am no tech here but I do have someone
helping with board work. I hate to keep bothering him until I have
narrowed
it down. Thanks allot Bryan




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