Service manual

Wells-Garnder Color Vector Monitor Guide
Page 22 of 73
temperature (and the resistors heat) caused the resistor lead to separate in the hole on the board,
while it still looked and tested fine.
NOTE:
Jeff Young from World Wide Distributors in Grand Rapids, MI reported some words of
caution about these resistors on Page 3 of the November 1982 issue of the Star*Tech
Journal:
"After fighting a problem in the Atari "Tempest" for three days and finding a silly
mistake, I thought I should write to you. Wells-Gardner Monitors #19K6101 use a 1.5-
ohm 10-watt resistor in location R610-R710. If you replace these resistors with standard
wire-wound units, the monitor will exhibit the "shakes" or "jitters" referred to in S*TJ,
Vol. 4, No. 7 "Service Tips", but the symptoms will be misleading in that R601 and R701
must be NON-INDUCTIVE. Please tell your readers about this problem as Atari and
Wells do not point out this requirement in the parts listing, and only put down the initials,
"N.I" on the schematic."
Symptom: R101 burns on power up
R101 glows red-hot and burns up to an open circuit every time the game is powered up (known
good deflection board; works in good monitor).
The resistor is burning up because of runaway current from the HV unit. You can confirm this by
replacing R101 and testing the deflection board in a known good monitor (or by putting a known
good HV unit in the monitor that is acting up); if R101 does not burn up then you know the HV
unit is the culprit. Whenever this happened to me, R903 on the HV unit has been the cause. It
will sometimes short and this causes so much current to flow to the deflection board that the
puny 15-Ohm resistor burns up. If this goes on for too long, Q101 may fail or occasionally R901
will burn up to an open circuit.
Symptom: Accidentally shifted P101 over 1 pin and power up machine
Although most of the connectors/connections are idiot-proof, P101 is not (due to the poor
placement of the key pin as the LAST pin). It can be connected shifted over 1 or more pins to the
right (although it should be obvious if you shift it more than 1 pin). After shifting it 1 pin and
frying the PCB, when you hook it up correctly, the spot killer LED will glow at 50% brightness
and you will get no video. The following parts will need to be replaced; Q703, R711, D702, and
C703 (C703 should be OK but replace it just in case if you can find a new one). Some caps may
have blown on the HV board, too.