Service manual

Wells-Garnder Color Vector Monitor Guide
Page 19 of 73
TEMPEST DISPLAY TROUBLESHOOTING (FLOWCHART)
The following flowchart is excerpted from the Star*Tech Journal, which means it was
originally in an Atari Field Service Bulletin.
Most problems in the Tempest display can be found by following the procedure shown in the
chart below.
No picture and...
+--------YES---- 5 amp fuse (F100 or F101)----NO-------+
| on Deflection PCB blows? |
\|/ \|/
Cannot get/keep +/- 28 Volts. Turn up brightness and contrast controls
Disconnect P600, P700, and<--------+ on HV PCB. Is there a dot in the center
P100. Power up monitor. | of the screen?-----------------+
| | | +-------+ |
\|/ | NO | | | YES |
Fuse still blows?-------NO-------+ | \|/ \|/ | \|/
| | | Is there +/- 28V on | Is there 180V on
YES | | | on pins 1/8 of P900? | pin 5 of P900?
\|/ | | | | | | |
Replace the following components | | NO | YES | +-----+ YES | NO
if shorted: D100, D101, D102, | | | | |
D103, C100, and C101 | +--------+ +----------------------+
| | |
+-----------------------+ \|/
\|/ Change or make sure C901 and C902 are
Check for Q102/3 collector short to 100uF at 50 volts. Check for a leaky
chassis. Replace the following compo- C905. If C905 is bad, also check or
nents if defective: Q100, Q101, D104, replace Q900, Q901, Q902, Q903. Is
D105, ZD100, ZD101, Q102, and Q103. there 180 volts on pin 5 of P900 now?-+
| | |
\|/ NO | YES |
Connect P100 and power up. Is | |
the +/- 28V on pins 4/5 of P100 Check resistors R100, | |
OK now?--+--------------NO------------->R101, R102, and R103 | |
| for open circuits. | |
YES | | | |
\|/ +------------+ | |
Replace the following components | \|/ |
if defective: Q603, Q605, Q606,<---+ Double-check the above transistors. |
Q703, Q705, Q706. Also look for burnt (open or shorted) |
| resistors R903, R904, R905, R906, or |
\|/ R907. | |
Connect P600 and P700 and power | |
up. Picture now?-------YES--------+---------------------+--------------------+
| |
NO | | Is picture "blooming" (does the image
\|/ +--->appear as though being viewed through
Check remaining transistors | a magnifying glass)? |
in the X and Y amplifiers. | | |
Then make sure the following-------+ NO | YES |
resistors are not open: R702, \|/ \|/
R703, R711, R712, R602, R603, >END<----Replace ZD902 on HV PCB.
R611, and R612. / \