Tech: Asteroids Repair Log
Phil
weeks ago:
Asteroids - problems and fixes - updated 3rd July 2002
Symptom: Sometimes explosions are variable length horizontal or
vertical lines instead of the normal collection of dots
Cure: Replaced the 74LS191N counters at D9 and H9 - (rev 04 board or
earlier) or D10 and H10 on a rev 05 board or later. However, other
74LS191N counters in the '9' (or '10' column depending on board
revision) can be affected, so it might be necessary to swap out others
and/or additional ones. Erroneous Horizontal lines are caused by the
74LS191's at either C9 (C10), D9 (D10) or E9 (E10) while erroneous
Vertical lines are caused by the LS191's at either F9 (F10), H9 (H10)
or J9 (J10). Note: the numbers in brackets represent the locations on
revision 05 (and later) boards.
Symptom: G05-801 monitor just 'glows', and these large screen-sized
glows move a little as the game plays
Cure: Replaced TIS98 transistor at Q602 on Deflection Board
Symptom: Game is dead (rev 05 board or later)
Cure: Had the two 'outer' EPROMs (test and program EPROMs) in the
wrong sockets!!! Position of these three is reversed when compared to
a rev 04 board or earlier. Middle one stays in the same relative spot,
the outer two are switched, ie the one in the third ROM socket goes in
the first socket, and vice versa.
Symptom: Diagonal line emanating from one asteroid
Cure: used a faster EPROM (300ns) for location N/P3
Symptom: Saucer fire sound is a brief buzz
Cure: Replaced the 14016B at M9 (rev 02 board)
Symptom: no thrust sound
Cure: Replaced 14016B at R12 (Rev 05 board)
Symptom: Arcing sound from EHV
Cure: Removed, cleaned and replaced HV Diode
Symptom: Player 1 and Player 2 LEDs flash rapidly, game is dead
Cure: Put F1 into it's socket (done as a test - not consistent)
Symptom: Background 'Thump' sound is very weak and not even
recognisable, but still 'thumps' when it should (revision 04 board)
Cure: Capacitor at C33 (.22uf Mylar) had a broken leg. Replaced.
Symptom: Very narrow vertical band in centre of screen, some activity
can just be seen in the band (revision 04 board)
Cure: TL082 op amp at C12 had been removed, as well as the two
capacitors at C98 and C119 (220 pf radial lead epoxy dipped 100V Mica
capacitors). Replaced.
Symptom: Onscreen objects and text consistently flick between normal
size and about four times larger, also extra spurious lines and
explosions
Cure: Replaced LS175N at M7 - pin 6 was stuck high, pin 7 was stuck
low.
Symptom: Dead board, no clock
Cure: Investigation revealed that the pull-up resistor at R29 wasn't
doing it's job, yet it checked out okay. Seems that it was
semi-shorted to the 6MHz line, so after extensive tracing located a
number of ICs that were supposed to have both connections to R29 and
6MHz which could have blown and shorted those lines to/from R29 and
6MHz. Eventually traced it down to the IC at A9 (an LS109AN) which had
suddenly died during testing - socketed and replaced
Symptom: Dead board, no clock
Cure: C18 (0.1uf capacitor) was bad - replaced
Symptom: game played but nothing on the screen except for a general
glow that varied as the game was played blind, X and Y outputs were
erratic
Cure: 7915CT voltage regulator at VR2 was bad - replaced
Symptom: All sounds feeble/distorted
Cure: LM324 at P11 was bad - replaced
Symptom: Game playing too fast, all sounds speeded up
Cure: Pin 4 at C5 had been cut (a known 'hack' to speed up the game)
so replaced IC (reconnecting the pin would have been sufficient, but
on this particularly board it was cut too close to the body of the IC
to allow this)
Symptom: Board ran for less than a minute (although screen fluctuated
in width, ie the X axis), then started resetting. Test mode indicated
that the 2114 RAMs at M4 and R4 were bad, but they weren't. Replaced
both the LS244's next to the CPU as some pins were rusty with metal
flaking off them. Still resetting.
Cure: Replacing socket for M4 RAM fixed the problem (socket was an old
one).
Symptom: Corrupt graphics - in game mode all graphics were split down
the middle (horizontally) and the two halves were then drawn besides
each other. In test mode, only two vertical lines and a diagonal line
were visible (revision 04 board)
Diagnosis: Pin 11 of the 74LS32 at B9 was stuck High, but replacing
this IC didn't fix the problem. This is the LDSTROBE signal that
connects to pin 11 of the 74LS191's at C9 up to J9, which were all of
course also High. Used a logic comparator and saw that this
highlighted the 191 at C9 as being faulty
Cure: Replaced 74LS191 at C9
Symptom: Test mode runs, but graphics are very corrupt, nothing
recognisable (Watchdog NOT resetting). In game mode, watchdog
constantly resets, LEDs flickering rapidly, cannot play game
Diagnosis: All tests done in test mode: LS42N at L6: pins 1 and 7 were
pulsing (should be High) but replacing this IC didn't help. Pin 13 on
D9 was High (should be pulsing) and putting a logic comparator on this
IC showed it was faulty. Replaced this and test mode was more
recognisable, ie there was an outline, and the diamond test pattern
was partly drawn, mostly in the lower left and upper right corners.
Also, the 'brightness' grid was present but it was too wide. The DIP
switch position indicators were also present, but were about four
times too large. So checked out the Vector Timer circuitry (handles
the Scaling for one thing) and found that pin 5 of the LS161 at D7 was
High (should be pulsing). This is fed from pin 2 of the LS42N at E7
which was also High (should be pulsing). The logic comparator
indicated that a number of the outputs of this IC were faulty, so it
was replaced. Test mode was then perfect, BUT game mode was still bad
- watchdog constantly resetting, spot killer on monitor flickering in
time with the start button's LEDs, BUT some frozen large asteroids
could be seen on the screen, along with the PUSH START and copyright
messages at the bottom overlaid along the entire bottom line with a
load of left square brackets '['. The LEDs also flickered rapidly,
game couldn't be started. Disabling the watchdog just showed the left
squares brackets scrolling right to left on the bottom line, but
nothing else, plus the LEDs were NOT lit.
Cure: ???
Symptom: (Revision 05 board) - Intermittently (*usually* soon after
power on) all vectors appear to be duplicated half an inch or so to
the right and connected by many lines. This only happens in the X axis
(ie horizontally).
Diagnosis: Freezer spray appeared to help but on replacing the suspect
IC (a 74LS191 at D9) the problem was still there. Further applications
of the freezer spray to other areas of the rightmost areas of the
board (when the problem was occurring) sometimes helped and sometimes
didn't. Sometimes moving the board had an affect, sometimes pressing
on the board (on the right side) also had an effect, therefore there
was either a bad joint or cracked track. Tried re-soldering all the
74LS191's in the '10' column but didn't help. Tried re-soldering the
two AD561J DACs.
Cure: Re-soldering the two DACs seemed to fix the problem
Symptom: Saucer and Ship fire sounds are slightly distorted (revision
05 board)
Diagnosis: As both the fire sounds are handled by two separate (but
identical) circuits it seemed unlikely that both had developed exactly
the same fault, so it seemed logical to assume that it was a problem
with a shared component. The only shared components were an LM324 at
L8, a 4016B at M9, an LS259 at M10 (triggers the relevant sounds) and
a 7406 at N9. However, swapping out these didn't make any difference.
Two other possibilities (albeit unlikely!) were the two 1N914 diodes
at CR3 and CR4, however replacing these also made no difference. I
then found that *sometimes* the fire sounds would be okay if I pressed
on the board (in no particular area). This board had a lot of
scratches on it so I re-checked the tracks for shorts or breaks - no
problems were found. The board also had a badly broken 8-way DIP
switch (the eight individual switches were broken to some degree) and
I didn't think this would have any bearing on the matter at all.
However, I changed it anyway while I was pondering the cause of the
distorted fire sounds, and after the DIP switch change the problem had
vanished! VERY strange!
Cure: Changed broken 8 way DIP switch
I am not averse to anyone copying this information or using it for
board repair (after all, that's the whole point in posting it!), but
it is NOT to be sold in any way, shape or form
Phil
Tntquality
helpful in bring back boards from the dead!!
Todd from TNT Amusements...our address is 1310 Industrial Blvd. Southampton PA
18966...website: tntamusements.com email:tntqu...@AOL.com. Our phone
number is 215-953-1188 then press 0 to skip automation. We're open everyday
except Wed & Sun 10 to 8
Ignus Fast
service for other collectors! Thanks!
Ignus
"Phil" <ph...@morris0.fsnet.co.uk> wrote in message
news:3d308abf...@News.CIS.DFN.DE...
Phil
wrote:
> In posting these repair logs to the public groups, you are doing a great
>service for other collectors!
Well that's the idea - it's nice to give something back. :-)
> Thanks!
No problem! :)
Phil