Service manual

Wells-Garnder Color Vector Monitor Guide
Page 20 of 73
CAUTION: When replacing the transistors mounted on the chassis, make sure the pins do not
short to the chassis. If the chart procedures do not solve your problem, call Atari Field Service.
We will finish off with a troubleshooting guide broken down by symptoms. Much of the rest of
this section is a transcription of repair notes from a Wells-Gardner technician. Just because
your symptom matches something in here is no guarantee that what he found wrong is the same
thing that is wrong with your board, but it is a good place to start. Most of the problems he listed
in his notes were due to manufacturing defects or incompetent repair work. Obviously, if your
monitor was working OK and then simply stopped, those things are not likely be your problem.
GENERAL MONITOR PROBLEMS
Weirdness between player one and two (Tempest machines only)
Display "implodes" during intermission screen between player one and player two and
sometimes on the "figure 8" levels (Tempest machines only): I thought I knew what was causing
this but upon further evaluation, my solution did not make sense (although it did work for me the
only time I had this problem). Until I get another board to fix that has this problem, I only have
general advice on how to avoid the problem. Adjust your game board and "shrink" the Y
deflection some and this should help. There are 3 sets of ROMs for this game and the "compact"
ROM set (revision 3 - only half the ROM sockets are used) is slightly different (the intermission
screen has some other stuff such as the copyright and credits information at the bottom of the
screen which "balances" it out) so the spot killer will not get confused and decide that the bottom
half of the screen is wiped out. These PCBs do not normally experience this difficulty.
DEFLECTION PROBLEMS
Symptom: Fuses F100 [and F101] blow on power up
Fuses F100 and/or F101 on the deflection PCB are blowing as soon as game is powered up. This
happens to a lot of people after they replace the chassis transistors. Sometimes they forget to put
the mica (plastic) insulator on the transistor before installing them, which allows the transistor's
case (collector) to short to the chassis (ground). A short can be present even if the insulator was
installed if the conditions are just right. Check all chassis transistors, particularly Q102, Q103, to
make sure the cases are not shorted to the chassis.