Asteroids PCB Troubleshooting Notes

Symptom: (Asteroids Deluxe) Game plays, however all there is for an image is four distorted vertical bands. Pieces of the Asteroids, as they moved across the screen, would jump between these vertical bands. Checking the inputs on the D-A converter at location C/D11, I noted the four driving signals coming from the 74LS157 at location D/E10 were stuck low, replacing the 157 chip cured the problem.

Symptom: This board worked OK after warming up for a few minutes. But before this 'warm-up' period, the board would reset, most often within the first few seconds after power-on. Resetting the board by a power-up would begin with random events, such as the beginning of the attract mode and a flash of the diagonal crosshatch, or a wild vector draw and a reset. This all happened very quickly, and could not be duplicated with each power off-on cycle. After these random events, the normal attract mode would begin. Within a few seconds, there was usually a reset or two, but not always. If the board was cold overnight, the symptoms were much more persistent. I noted that a press of the reset button did not produce the same result as a power-on reset. The manual reset button worked correctly, (after release, it always started with the beginning of the attract mode), while the power-on reset included the random events. Along with these random vector events there were usually a few quick chirps or clicks of audio. This failure was caused by a defective 74LS14 chip at location B6, part of the power-on reset circuit. After replacement, it powers up to the attract mode every time, even on the overnight test. It should be noted that the display power was always live during these power-on tests, so I could see the random events, (whereas on a cold monitor you couldn't see anything until the tube filament was up to temperature).

Symptom: (Asteroids Deluxe) In test mode, the diagonal crosshatch had lines going out of the box. In attract mode, as long as there were no images of your ship, or the enemy ship being displayed, all appeared OK. Your ship, as well as the enemy ship, was displayed so large that it "overfilled" the screen. An interesting side note on this symptom - while playing the game, when the enemy ship came out, the "thump" sound slowed down, as it took so long to draw this giant image. In fact, a couple seconds after the enemy ship came out, the game would reset. (Because the watchdog circuit failed to get serviced in time). These problems were caused by a failed 74LS175 chip at location M6.

Symptom: Game actually plays, however; everything displayed on the monitor was very small, but looked to be in the right place. All moving objects appeared as somewhat larger than just bright dots. In test mode, there was no diagonal crosshatch, but by turning the brightness up you could see a dot in the lower left and upper right corners, connected by a diagonal line between the two. During testing, I noted the counters in the vector timing circuit were NOP, due to the 'GO' inputs being incorrect. This signal originates from the dual J-K flip-flop at location A9, specifically the first half of the 74LS109 chip. Replacing this part cured the problem.

Symptom: (Asteroids Deluxe) In test mode, the diagonal crosshatch displays almost correctly. The only visible problem is where it shows how many ships per game - these ships are stacked nearly on top of each other, and curve up to the right. In game mode, the largest Asteroids (as they 'roll' across the screen) change shape, from sometimes correct, to oblong. The enemy ship is in two pieces - the outside of the ship is formed OK, but the horizontal line that's supposed to be inside the ship, is instead off to the left, completely outside of the ship. The enemy fire 'bullets' originate from this horizontal line, instead of the ship. These 'bullets' also flash on and off as they travel across the screen. Your ship was displayed correctly, however its 'bullets' also flashed on and off. Fix: The 74LS42 at location E6 was bad. Replacing that chip corrected the errors.

Symptom: (Asteroids Deluxe) The high scores are displayed as BBFFBDFF for all three of the top scores / names, sometimes a character or two is different than that. You could not erase the high scores by simultaneously pressing rotate right, rotate left, thrust, and fire while in test mode. The screen said 'erasing', but the same characters came back immediately when switched out of test mode. Checked the -30 volts going to EAROM at location N9 pin 14 - it was about -28.5 volts, that's OK. The EAROM itself was replaced, no help. The problem turned out to be the 74LS175 chip at location N10. After replacement, board is 100% functional.

Symptom: No picture in test or game mode. The watchdog circuit not being serviced is causing a reset pulse to be generated every 1/2 second or so. Here's a trick I use: Removing a RAM chip causes it to be identified in during self-test; in this case I removed M4 because it was in a socket. (2 higher beeps followed by 1 low beep). This stopped the resetting, because with a RAM error, the program does not attempt to write a vector for display. Therefore the problem is in the vector drawing circuitry, the 'finished drawing a vector' signal never happened. If this signal doesn't occur before the watchdog chip 74LS393 counts 32 pulses of the 3KHz, there will be a reset pulse, which was exactly the case. The problem was in the timer signals connecting to the inputs of state machine PROM at C9, specifically the 'ANDing' of timer (3) and timer (0) via chip at E6 - pins 13, 12, and 11. Pin 11 (the output) was not following the 'AND' rule, (both inputs 'hi' for a 'hi' output). In fact, there was random noise on this output. Other gates in this chip also deal with decoding the timer signals, and it appeared the output of failed gate was responding to input changes on the other 3 gates. Replacing the chip 74LS08 at location E6 solves the error, and the board works again.

Symptom: Game actually plays, board doesn't reset. Problem is that the displayed image (test screen or the game mode) rapidly scrolls up, and to the left. Occasionally, this scrolling would appear to reverse directions. If this were a raster-scan type monitor, the best description I could give would be the horizontal and vertical holds weren't working. But because this is an X-Y monitor, there are no such signals. However, there are X and Y position circuits, and there is obviously something wrong in these areas. It appears these counting circuits are not being told where to start. The images are being drawn correctly, just in a different starting position every time the state machine executes. The failure was being caused by the X and Y position counters not receiving the LDSTROBE pulse (active low) in on pin 11 of the six 74LS191's. This signal originates from an OR gate (74LS32 at location B9 pins 13, 12 and 11). Replace the 74LS32 chip at B9 and the display image is stable, this board is ready for 'burn-in'.

Symptom: On a power-up, test mode screen, diagnostics, and game play are fine. The problem is when you activate the test switch, screen goes blank and board 'locks up'. Switching out of test at this point will not return to game mode. The only way to get out of this locked condition is to power off - on, or press the reset switch. The problem was in the watchdog reset circuit, I noticed the board would not go into reset even by removing one of the program chips. Failure was 74LS08 chip at location C6 - pins 8, 9, and 10. both inputs 'hi', output was stuck 'low'. Replace C6 and this problem is solved, board now works 100%.

Symptom: (Asteroids Deluxe) In test mode, just goes beep beep continuously, with no display. In game mode, no display. Either mode, watchdog circuit would allow reset every half second or so. Reason: Hardware is not sending signal to CPU that it is finished drawing a vector. This was caused by a 74LS161 chip at location C6, 2nd counter in chain in the vector timer circuit. This chip was not completing its count; there was no 'carry' signal on pin 15 to allow the next stage counter in the chain to count. Replace 74LS161 and now board works perfectly.

Symptom: Game plays fine - after several game plays, no resets... However; placing the board into self-test gives two low tones - both working RAM bad? Not the case, as suspect RAMs work fine on another board. All of the components / circuitry dealing with addressing / data of RAM checks out 100%. This problem was caused by the program chip 143-02. The Asteroids self-test screen / testing device / and an Eprom programmer verifies this part as OK, but the symptom travels to a different board when this suspect 143-02 chip is used. I installed a newer (faster) 2716 chip to correct these error. - suspect device was 1980 Fairchild type, couldn't determine speed / date code because of the labeling ink being worn off the top of chip. After replacing 143-02, board now goes into test without mistakenly identifying the two work RAM as bad. * Update 2 days later- all still OK, ready to ship. * 2008 Update over a year later - board still functions 100%.

Symptom: Test pattern is slightly askew - lines that meet which should be inside enclosed box protrude slightly out of box in lower right - while in upper left, lines are cut off slightly at the box where they should meet - worse yet, in game mode - moving objects jump horizontally across screen as they change position - about the width of the large asteroid. The moving objects are still shaped correctly. Problem was pin 5 and 6 of 74LS273 at location J7 - both had identical outputs, apparently they shorted inside chip. This chip deals with the X position data to be loaded into the X position counters. Replace 74LS273 chip at J7, and objects scroll across screen correctly again.

Symptom: In test mode, cannot see a picture, however you can hear the beeping sounds when you activate switches. (Turning up the brightness you could see a faint diagonal line with 2 brighter dots, one in the lower left corner, and one in the upper right corner, with the diagonal line connecting them). In game mode there is a '56789012345678901234567890123456789012345' flashing on and off across the screen. The board resets every time it flashes. Then there is this is a very strange second half to the symptom - I tried replacing the 34602 custom fuse prom at location C8, and inadvertently missed on pin 8 - the ground pin of the chip was sticking out of the socket - and the board worked.... Putting the ground (-) pin back in the socket causes the failure again, described above. So I scoped the inputs on C8 and found pin 2 input was not going fully hi or low - this signal originates from a 74LS08 at location E6 pin 3 - replaced 74LS08 at E6 and now the board doesn't work with the (-) pin of C8 lifted out of the socket - but it works perfectly when the pin is put back into it's position.

Symptom: In test mode, diagonal crosshatch displays, the brightness graduation scale is there, but has an extra 45 degree line about an inch long pointing down and to the left. In game mode, all that was displayed was the "P" in press start, and the same 45-degree line as above. (Dipswitch set to free play). In both modes, there was a constant reset, and then would display symptoms as described above. Problem was 7404 IC, location B5. (Other inverters in this IC are used in the clock circuit). Specifically, pin 4 of this IC was stuck in the 'hi' state. Replaced 7404 at location B5, and board is good again.

Symptom: Board would work if cold - As it warmed up, picture would be ok for a few minutes (board cold) to a few seconds (board still warm, turned off for a short time).
When the problem happened, picture would get smaller, become distorted, and then turn into a swirl of lines. Shortly after that, the swirl of lines would go upwards and 'off-screen'.
Note that if the board was warm, failure could happen before picture tube filament warmed up, therefore you might not have even seen anything on display before picture 'disappeared'. Monitor's fault LED (Spot-Killer) would then be ON.
Problem was in the -15 volt power supply area. The 7915 voltage regulator 's output would range from -15 volts to just below zero volts, after regulator heated up. Replacing 7915 at location VR2 corrected the problem, and board is still OK now after 72 hours.

Symptom: In test mode, all is OK. Will not go into game mode, watchdog would keep resetting. Problem was in the NMI signal going to pin 6 of the 6502. The frequency of the signal will change how fast the game runs - the frequency being zero as in this case, the 6502 microprocessor was waiting to be 'interrupted'. This signal originates from a 74LS161 chip at location C4, replaced this chip and board is 100% functional.

Symptom: In test mode, diagonal crosshatch pattern bad, one box in lower left of screen, with a few diagonal lines, and another similar image in the upper right of screen, but no lines surrounding the 'box'. In game mode, you could play, but the starting asteroids were 1/2 the size they should be, and when they were hit, they turned into very tiny asteroids. The text was also very small. Problem turned out to be the 74LS175 latch at location M7 - although the latch signal on pin 9 was active, all the outputs were hi. Actually the outputs were somewhere between hi and low, measuring about 1.5 volts. Replaced M7 and this board works right again.

Symptom: Board works, and would be OK if there wasn't a 'pulsing' in the position of where the line is is being drawn on the display. This 'pulsing' is actually a 60-cycle waveform being introduced into the X and Y output voltages. In this particular case, the distortion added into the picture was minimal, but was not acceptable to my standards. Diagnosis: The +15 volt section was trying to regulate an input voltage just slightly over 18 volts supply - not quite enough supply - the output voltage had a 60-cycle 'hum' of about a .150 volt. The reason why the supply was at approximately 18 volts instead of about +22 to +23 volts, (normally this condition will cause fuse failure, explained below) was because a 4016 chip used in the fire sound circuit was drawing too much current via the +12 volt regulator VR1, which still measure +12 volts. The fire sounds still sounded OK, they were not distorted. The 4016 chip was actually still functioning - but it was warm to the touch. A CMOS chip such as the 4016 should never feel warm, as they do not draw enough current.
It should be noted that I use a transformer for the 36 VAC in series with a control circuit, which "kicks in" if there is too much current drawn through the secondary. Over current through the supply transformer (via the board. or a direct short on the secondary) will not cause any fuses to blow, sparks, burn, etc. If there is is short on the board under test, no further damage will occur, (example: a shorted regulator will not blow the 1N4004 diodes out). All that will happen is a lamp on my test fixture will glow brighter, because of the increased voltage drop across the load in series with the transformer. I have this safety feature because the condition of the many different boards I receive is unknown, and there are times that shorted boards do come in.
The above board still worked, with the visual discrepancies as described. If it was installed into a game cabinet, I would say that the fuse in the 36VAC HI circuit would blow after a short time. I do not put boards into a cabinet for the initial tests, having seen this problem before, I notified the customer to look for a bad fuse, which he found.
Note that I have also seen these symptoms caused by one of the LM324 chips in the audio section drawing too much current. Usually if this is the case, the distortion in the picture will be much greater, and there will be a loud hum in the audio (failing final output LM324) or incorrect firing sounds (failing LM324 voltage modulation for the 555's).

Symptom: Test mode diagonal crosshatch is way off - lines where they don't belong, lines going out of box, the dipswitch representation curves up. The further right the one's and zero's go, (showing the position of each switch), the more stretched up they appear. In game mode, the asteroids are disfigured, they don't make an 'enclosed' asteroid. Any text displayed skews up at about a 45-degree angle, and letters are not formed correctly. I have seen very similar symptom where the problem was in the rate multipliers (7497's), but this time it wasn't. The problem was a 74LS191 in the "Y" position counter, the first one in the chain at location J9.

Symptom: Test mode displays OK. When in attract mode, game resets every 4 - 5 seconds. Screen looks like it starts out right, the problem occurs as soon as the initial 4 asteroids start their scroll across the screen. One of the asteroids shows up in 2 places, across the screen there it is again, but dimmer, appearing to flash on and off rapidly. This 'clone' would scroll at the same angle as the original. The 'attract' mode would last a few seconds, until the saucer came out, the copyright text would get brighter, part of it would shift position, a diagonal line would flash, and then board would reset. If the dipswitches were set for free play, then every time 'Press Start' would flash, it was similar to when the saucer came out above. Or, upon inserting a credit, and the screen would try to display 'Press Start', the same would happen as above. Occasionally the test screen would flash in the mix, for no apparent reason. This problem turned out to be the 74LS74 chip in the state machine. Replaced the 74LS74 at location A7, and the board is back up.

Symptom: (Asteroids Deluxe) Test mode screen display is OK. When in attract or game mode, high score was displayed as curving up to the right, the more text that was displayed. The Atari copyright logo zigzagged up and down, but the "INC" was Ok. Game Over, Credits, etc were displayed Ok. As the asteroids rolled across the screen, they would jump around about 1/4 inch at random from where they were supposed to be. Your ship also did this, as it moved. When the Asteroids were broken into the smallest pieces, they turned to flashing dots. The enemy ship was displayed without error. Fix: The 74LS161 at D6 (the first one in the chain for the vector timer) was bad. Replaced, everything is displayed correctly.

Symptom: In test mode, just a high pitch beep, followed by a diagonal line that scrolls further up the screen with each beep. Right after power-up, sometimes there was the test screen for a few beeps, but it would go away, turning instead into the scrolling diagonal line. Noted that 8-bit latch 74LS273 at location F7 was not transferring data from input to output, in particular the timer outputs, checked the 'clear' pin 1, found that just by putting scope probe on pin 1 that it would cause the test screen to come on, but would still reset. Replacing the chip driving the clear function, a 74LS08 at location K6, fixed the board so it works in test mode and game mode.

Symptom: Test mode - instead of diagonal lines, there is a small stripe in center of screen, and small bright dots where dipswitch / brightness scale should be. In game mode, you can play it, but enemy ship is a bright line, asteroids are either too large, or just small dots, text is very small. Fix: 74LS83 adder chip at location M6 was bad. Replaced that chip, and the board is OK.

Symptom: (Asteroids Deluxe) In test mode, diagonal crosshatch screen is bad, it's made up of 2 boxes, 1/4th the size of the screen, one in the lower left area, and one in the upper right area of screen. Both boxes have only a couple diagonal lines. In game mode, there are only large asteroids, they're 2X the size they should be. When you shoot them, they split, but split into same 2X size asteroids...they never get any smaller. Also your ship, and enemy ship, is almost as large as the 2X sized asteroids. Fix: The 74LS175 chip at location M7 - all the outputs were non-changing, because the latch signal on pin 9 was stuck "hi"... the problem was the 74LS32 'OR' gate pins 8, 9, 10.. it was bad... replace 74LS32 chip at location N6 - replaced and the board works fine.

Symptom: Test pattern looks OK and board allows you to play the game without resetting, however, the "Press Start" is illegible, the amount of ships you have remaining curves up, and some of the smallest asteroids are about half the size they should be. Not all of them, but a few are. Sometimes the text would jump around. Strangely enough, I got in 2 boards on the same day that had these exact same problems, and both of them had the same failed chip. Problem was 74LS83 adder chip located at M6. Pin 6 output was not going to it's "hi" state completely - only about 1.85 volts "hi". Replace chip and all is fine on both boards.

Symptom: Asteroids only move up/down no left/right, also in wrong place. The game would play without resetting. In test mode, the diagonal crosshatch had lines drawn outside of box, this test pattern was about 50% correct, and 50% random. Problem was the 74LS273 chip at location J7. All of this chip's outputs were stuck 'low '. Replaced that chip, and the graphics are correct again.

Symptoms: Using GLS1 tester, program cannot be read correctly A(10) noisy… replace 74LS244 location B2...then:
Just draws lines at random, resets - replace 24LS273 at location F7 (timer 1 was stuck low), then:
Almost right - but diagonal lines look a little jagged in the up/down direction - replace 74LS374 location B10. Board is good afterwards.

Symptom: Test mode passes and diagonal crosshatch OK. When taken out of test, attract mode starts, asteroids just beginning to move, 1/4 second later, resets, continuously does this. Also has a row of what looks like copyright symbols (or the character "c") running together across the bottom of screen. Fix = replace 74LS191 at J5. This symptom is exactly what it looks like if you remove the 74LS191 chip.

Symptom: (Asteroids Deluxe) Test mode passes and diagonal crosshatch displays OK. Try to start a game and it resets immediately. In attract mode, board would not reset. However, if dipswitches were set for "Free Play" mode, when the text flashed "Press Start", 90% of the time it would display "PBress Start" (upper case B where it didn't belong, it could've been an '8'). Occasionally, it would change from a 'B' character to your 'ship' character displayed at 2-3 times the normal size... Sometimes when it did this, it would also place this larger ship in a couple more places on the screen. The 'copyright' line of text would change from '(C)(P) 1980 ATARI INC' to something illegible for the first 10-12 characters ... During attract mode, after some of the large Asteroids were broken into smaller pieces, the "Press Start" would suddenly be OK - but the copyright line of text would be in two places on the screen at the same time... Also, if you tried to start a game, the last thing it would do before resetting (it seemed), a string of bright 'C' characters would display across the bottom of the screen. Note this part of the failure is very similar to previous problem. Fix: pin 3 of 74LS191 location K4 was counting OK, but during the "low" period, instead of zero volts, it was approx 1 volt - replacing 74LS191 chip fixes board.

Symptom: Game works sometimes for an hour, sometimes for a few seconds, then resets. Using GLS1 tester, found that randomly all the program chips and all the memory read failed, due to data bit DB(1) gets stuck low... this could be the RAM, program (which was replaced, and wasn't the problem) but it turned out to be the chip that reads the dip switch - a 74LS253 pin 9 at location P6. Output was going low when it wasn't supposed to - replace and board has been running 2 days now all OK

Symptom: Game plays, but picture is down too low on screen, the Y adjustment works (height can be adjusted, but still too low on screen)... replaced TL082 chip at location A12 ... fixes problem

Symptom: Display only shows on top half of screen, and the bottom half is displayed in upper half of screen, too, but it's backwards.... this is caused by the inverted signal for the cocktail version player 2 is getting through when it shouldn't. Fix was replacing 4016 chip at location B12. This board had a bad 4016 chip in the sound section also, in fact all five 4016's on the board had the same date code - two going bad means do not trust the three remaining 4016's - change them out, or down the road the board will fail again.

Symptom: In self-test mode, 2 smaller boxes on screen instead of test screen, looked like 2 smaller test screens, but with less diagonal lines contained in boxes - problem: (this board had 191's instead of 161's for the vector timer) replaced IC C7 second 74LS191 counter in chain, and the board works again.

Symptom: (Asteroids Deluxe) in test, 2 smaller boxes on screen instead of test screen, similar to above problem... in lower left box there were less diagonal lines than a normal test screen, while there were no lines in upper right box - problem: 1st counter in chain in vector timer circuit. Replace 74LS161 at location D6... corrected problem.

Symptom: In self-test mode, same as the symptoms above. The fix was also the same, although because this was an Asteroids board, the reference designator was D7. The first counter in the chain (vector timer) had failed. Normally I don't enter duplicate type symptoms, unless they are noteworthy. One chip of the three counters used in the vector timer circuit was a type SA 74LS161 with a date code of 8046, the other two were DM74161AN's, with a date code of 9316. Obviously the two similar chips had been changed sometime since 1993. Note the failed chip is in the bad chip list, at the top of this page. (SA 74LS161 with a date code of 8046) 9-22-2007

Symptom: (Asteroids Deluxe) Same as above three symptoms, and the same fix - the first counter in the chain of the vector timer was an SA74LS161AN type, the second and third were of the Texas Instruments type. The SA type at location D6 was bad - replaced and all is OK. It appeared this was factory installed. This is not surprising, as there are a lot of SA manufactured chips that fail. It had a date code of 8103.

Symptom: As Asteroids moved across screen, sometimes 1/2 of the asteroid would jump about 1/4 of the way across screen, while the other half of asteroid would be in the right place. This actually happened to all moving characters, depending on where they were at in the screen - replace 74LS191 chip, first counter in chain for the X position counter.

Symptom: Game plays, but all moving graphics are short vertical lines. The lines are where the moving objects are supposed to be, and move around OK. Diagonal crosshatch screen is only bright vertical line on left & right sides of screen, Text info/brightness graduation scale displays as 3 vertical lines. Problem was defective 7497 chip at location K8

Symptom: Game plays, but all moving graphics are short horizontal lines. The lines are where the moving objects are supposed to be, and move around OK. Diagonal crosshatch screen is only bright horizontal line on top & bottom sides of screen, Text info/brightness graduation scale displays as 3 horizontal lines. Problem was defective 7497 chip at location F8.

Symptom: Power up board, nearly all different sounds (explosion, saucer, fire, etc) come on immediately.... no picture, no test function. Pressing the reset button on the board has no effect, first thing to do is check clock - clock was ok, it was driving the 74LS161 chips - but no output/count on 161's - because pins 7, 9, and 1 are 'low', 161 chip is not enabled... pull up resistor R29 pulls up to 'Hi' these inputs, as well it must pull up several more inputs, (another 161, 6502, 157). Resistor R29 checks OK at 1K ohm. Something is pulling down this point of the circuit. It could be any one of the 15 inputs this resistor pulls hi. Turned out this time it was one of the 161's. Replaced both 74LS161 chips at C4 and C5, and board works perfectly. It should be noted that I have seen these exact symptoms also caused by pin 1 of the 6502 chip (incorrectly inserted), bent just enough to be inserted into pin 2's position in the 40-pin socket. As pin 1 is the (-) supply for the 6502 chip, with it sticking in pin 2's place, this causes the pull-up resistor to drop almost all of the 5 volts across it, meaning all inputs R29 are supposed to be pulling hi, are then low, which results in no RESET.

Symptom: During self test, 2 lower beeps, signifying both working RAM bad... game plays for a few seconds and resets...both RAM being bad is unlikely... using GLS1 testing device I noticed exactly half the data in working RAM is good, half is bad ... this means a single address line problem... found pin 16 (AB8) of working RAMs was stuck high.....fed by output from X-OR gate 74LS86 at P5 pin 6... this was bad (stuck hi)... replace 74LS86, corrects problem.

Symptom: game plays OK, but vector graphics on the screen are all jumbled towards the center of screen, with curved lines, its so distorted you can't really tell what's going on, you can tell when saucer comes out because a patch of the screen gets brighter... The first thing I'd suspect is problems in the output power supply... checked both regulators plus and minus 15 volts OK... next step check the 4016's in the output stage...first check that the power pins of both 4016's are: (pin 14 = positive 7.8 to 8.1 volts) and (pin 7 = negative -7.8 to -8.1)..found pin 14 on both 4016's was at about +5 volts, (pin 7 negative was OK): Usually when the power pin(s) on the 4016's are bad it's one or both 4016's drawing down (or up) presenting a load on power source. Replaced both 4016's, voltages were correct, and picture looked perfect.

Symptom: in test, would draw diagonal crosshatch OK, but also draw brighter line lower left corner to upper right corner, then reset, then do it over and over. With watchdog disable held low, (during test) pin 2 of 74LS251 halt always low......... when not in test, would draw "P' (if in free play "Press") or draw coin multiplier (1 or 2 coins per credit) then immediately after draw a bright line like in test, then reset. Fix was 74LS670 chip (or 74LS170) at location J4 - pin 6 of J4 when probed, would sometimes cause flicker, like it was trying to draw random characters - noted 3-state condition on outputs of this chip appeared "off" always

Symptom: using GLS1 tester, program 143-02 and working RAM D2 and E2, 50% of time would be randomly read (143) or randomly written/readback (RAM). 144, 145 and vector ROM/RAM chips read OK. In test and in game modes, no crosshatch or play, just constant resetting- problem was 74LS157 chip F3 top in chain - ab(0) and am(0) appeared shorted together - internal short in 74LS157 chip between pins 10 and 11. am0 ties to State machine prom pin 5... causing the state machine to execute randomly

Symptom: The large asteroids (before they're shot and get smaller), are OK. Any smaller asteroid, or your ship, or enemy ship, are too small. Other than that, test, diagonal crosshatch, game play, all OK. Problem was 74LS175 chip location M7 pin 2 was stuck low. This chip latches the scaling factor to inputs on the adder. Replacing this chip corrects the problem.

Symptom: All there is for a display is a single vertical line off to the right of the screen. You can see all of the X-deflection is bunched up into the line. The line moves left and right when adjusting the X potentiometer. This problem was corrected by replacing the TL082 chip at location C12.

Symptom: All there is for a display is a single horizontal line in the upper half of the screen. You can see all of the Y-deflection is bunched up into the line. The line moves up and down when adjusting the Y potentiometer. This problem was corrected by replacing the TL082 chip at location A12.

Symptom: (Asteroids Deluxe) All seems OK, until explosion image happens. The explosion 'particles' then are really bright, and expand out to fill the whole screen. This problem was not a failed chip, but 2 pins on the back of the board (pins 12 & 13 of 74LS175 at M7) were bent over shorting to each other.

Symptom: no game play, constant reset. In test mode, 2 higher beeps followed by two lower beeps. Replacing socketed RAM no help. Early type board, two middle / two outer RAM chips are Exclusive enabled. This board had been worked on by individual, and trace going between ram chips( ) was broken and shorted to adjacent trace. Also one RAM was bad. Repaired. Board runs fine for 10 minutes or so.. and then picture is squashed (only in horizontal direction). Typical secondary failure on Asteroids board after not being run for years... Replace 4016 at location B12

Symptom: RAM, ROM tests OK. On power-up, or right after a reset, all video would be was a large saucer 4X in size scroll across screen multiple overlay appearance maybe 20 ships... then reset, and do it again. Fix was to replace 74LS670 chip (or 74LS170) at location J4. If you replace a 670-type with a 170-type, remember the 170-type needs the pull-up resistors on the outputs, I use a 2.2k by 9 sip pack.

Symptom: ONLY diagonal flash across screen no characters - problem was 74LS191 at J5 - pin 6 was stuck hi, this pin must go low for normal operation...
In test mode, all RAMs, ROMs Ok and test pattern looked fine.

Symptom: In test mode, the crosshatch pattern is missing half of the diagonal lines, they're also not exactly
making 90 degree corners. The line that's supposed to make up right hand side of 'box' is missing (3-sided box). In game play everything is fine, except for your ship - as you rotate, most angles you're pointing, the ship changes shape from triangular to random, sometimes it just looks like a single line, other times it is only 2-sided. problem was DVX3 input on rate multiplier 7497 at location J8. Replaced 7497 at J8 - all OK.

Symptom: Works fine in test mode, when in attract mode everything starts out fine until saucer comes out - then one of the large asteroids would flicker and sometimes had an extra line protruding off - If the game dipswitch settings were set for free play, then as "Press Start" would flash, then the same large asteroid would flicker, sometimes get smaller, and when the saucer came out more flashing objects and then a reset. In game play, game would last about 5 seconds or so and then reset. Problem: A(10), Ab(10), AM(10) signal path had noise in signal. Pulling up A(10) input pin 8 on 74LS244 via 820 ohm resistor to +5 volts caused problem to go away. Replaced 74LS244 chip at location B2 cured the error, no longer required pull-up resistor.

Symptom: Not a constant reset problem, and test pattern crosshatch looks nearly normal...some lines in top center and bottom center of crosshatch pattern go outside the box, still have nice 90 degree angles, but the "points" are not contained. Dipswitch representation as well as "brightness scale" is short lines that gradually curve up and to the right. In game mode, plays OK except for graphics. There is what looks like a "baseball diamond" constantly displayed, some asteroids have 3 extra lines , kind of like part of the "baseball diamond" moving around with them. Some asteroids are just three 90-degree lines, but move around screen OK.... Also… Some smaller asteroids were OK - but every 1/2 inch or so they would jump either up or down as they traveled across screen. Also any text appeared as the wrong letter/symbol and curved up and to the right, one of the letters looked like your ship twice the size of normal. Fix: Signal DVY6 pin 12 of 74LS273 at H7 was stuck low - replaced.

Symptom: (Asteroids Deluxe) game plays, but all the Asteroids are bunched up together, even after you shoot them...they stay in the same cluster.... replace Pokey chip location M7/8.

Symptom: Electrolytic capacitor blown apart - didn't power up board until cause was determined: Here's what I found / repaired / replaced:
First noted that capacitor at location C68 was blown apart - replaced 1ea 470uf at 25 volts capacitor. Check diodes, which supply capacitor - 2 diodes shorted. Replace 2ea 1N4004 diodes reference CR10 and CR11. Now, +15 volts OK, but -15 volts bad. Replace 7915-type voltage regulator reference VR2. +15 volts and -15 volts OK afterwards, but +8.2 volts and -8.2 volts both bad - cause was 4016 chips that run on these voltages were drawing too much current, replace 2ea CMOS 4016 chips at locations B12 and D12. Next, +8.2 volts ok, but -8.2 volts is approx -3.0 volts. Replace 8.2 volts zener diode at reference CR14, this fixed the -8.2 volts. X and Y outputs are now incorrect, cannot zero-adjust with no signal - all 4 OP-Amp chips were bad - replace 2ea TL081 chips at locations B/C12 and E12, and 2ea TL082 chips at locations A12 and C12. Next, X and Y outputs are adjustable, but still no X or Y deflection - replace both D-A converters, AD561's at locations B11 and D11. Now, X and Y outputs work as designed.

Asteroids Type PCB Troubleshooting Notes		Other PCB's tested
for your Asteroids video game
Computer Aided Testing System

	Test Procedure
	Test Examples
	Test Table
	GLS1 Electronics Home page
	Asteroids Deluxe Repair
	Asteroids Repair

	Have a Question? Live chat here, enter any user name, (Leave password field blank, no need to register)