Star Tech Journal

STAR*TECH Journal
I
Aptil 1988
Data East Vigilante Power Supply Short
Neal Zook
Data East Service Department
San Jose, California
PROBLEM
Mounting feet shorting out power supply.
The Vigilante conversion kit comes with
metal mounting feet to facilitate mounting
the PCB set to the cabinet wall. The mount-
ing hardware supplied consists of four
mounting feet with screws and fiber wash-
ers. The fiber washers are supposed to be
installed between the PCB and the metal
mounting feet as shown in Figure 1.
CAUSE
We have reports from the field indicating
that the fiber washer has been installed
between the screw and the PCB as shown in
Figure 2. The PCB foil pattern has +5 volts on
the component side and ground on the sol-
der side. This mounting configuration can
cause a shorted condition between the +5
volts and ground.
Reports indicate that this can cause damage
to some types of power supplies and can
cause failure to the Vigilante PCB.
c:.-=J='*••~ f1e.£0
WASeER
Figure 7 (correct)
Figure 2 (wrong)
SOLUTION
When using metal mounting feet, always
install the fiber washer between the PCB and
mounting feet as shown in Figure 1.
Wells-Gardner 194901 Brightness Problem
Sam Cross
Godwin Distributing Company
North Little Rock, Arkansas
PROBLEM
Rippled brightness or problems with bright-
ness consistency.
CAUSE
C702, a 10 microfarad capacitor at l00vdc
with radial leads has failed, causing bad
filtering on the B+ boost voltage supply to the
final color output transistors.
NOTE
Even though the B+ boost voltage is
180vdc, the monitor design is such that the
negative lead of C702 is connected to the
positive B+ voltage of 125vdc, and this a
allows use of a capacitor without such a WI'
high voltage rating.
***