STAR*TECH Journal
•
November 1987 [3)
Data East
KID NIKI Video Glitch
Atari ROADBLASTER
Rolling Roadway Fix
By Neal R. 1.ook, Olstorrer Service Manager
By Ritchie Khodadadi
Data F.ast USA, Inc.
San Jose, califomia
PROBLEM:
Glitches in video.
SYMPI01S:
Data F.ast's Service Departrrent has
repaired several KID NIKI pcbs suffering
from video glitches in and around the
rooving character image. 'lbe glitches are
noticeable when the Kid Niki character is
on the screen and appears as lines
displayed next to the character. We have
found that this problem may show up
intermittently on certain version pcb
sets.
Atari Field Service Departnent
Milpitas, califomia
SYMP.OCt-1:
Roadway rolls vertically. You can see this
on dedicated ganes and kits. At first, it
looks like a typical vertical sync
problem, but actually it is caused by a
bad SP CLK pulse which throws off the IN1'3
(Mid Screen Interrupt) and the roadway
starts to roll intermittently at the
half-way point.
Wl'E:
Refer to sheet 14 of SP-298,
Schematic Package.
FIX:
IDENI'IFICATIOO:
A
•
The pcb sets that are affected can be
indentified by separating the individual
pcbs and examining the M62-B-B pcb (the
bottom board) . The M62-B-B pcb will have
either four 2149 type RAMs (locations
3E, 3D, 2E and 2D) .Qt. two 2018 type P.AMs
(locations 1D and lE) . The only pcbs
affected are the units that use the four
2149 type RAMs.
SOLUl'ION:
The problem is caused by a slight
difference in the access tine between the
2149 and the 2018 RAM devices. To correct
the timing differences and eliminate the
video glitches, install a 100 pf capacitor
between pin 1 and pin 8 of the 74LS157 at
location lH on the M62-B-B pcb.
STAR*TECH JOURNAL, November 1987, Volume 9,
umber 9. Copyright [c) 1987 by Star Tech
Journal, Inc. All rights reserved. Address
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Please remit payment in US funds.
Usually very sirrple and a matter of
replacing the socketed speech chip or a
transistor on LSI cartridge PCB.
'Ibe key to diagnosis of this problem is to
check -5 volt regulators (Q2 or Q3),
79L05/7905, if output is less than -5
change it.
If -5 is ok, then use a scope and look at
SP CLK at pin 6 of 16H (TMS5220), this
LJignal has to be 8 volts P-P and any less
than that won't work. If so, try replacing
16H or Q6.
POSTNASTER1 Sand address changes io
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