Atari Jet Fighter. PCB Repair Part 2...

Well after have a fair amount of play recently and being switched on for 10+ hours, Jet Fighter developed a fault when switched on a few days ago...

In attract mode the Black Jet was erratically flying backwards, not something I'd seen before with this board. When you started a game the Black Jet carried on flying backwards and the left/right rotate controls we not working for either Jet.

I started probing around the vertical and horizontal motion counters to see if I could track down the issue, there are four signal J1C0-J1C3 which are derived from a 64-bit RAM IC, probing these for the Black Jet circuit I found that they were all stick high and not pulsing as I would have expected.

This board is quite nice as the Black & White Jets have pretty much identical circuitry so it was easy to compare one with the other.

Checking out the other pins on the RAM, I found that the W/E pin was being held high, I traced this back to an LS7432 (2-Input OR gate) and confirmed that the output was stuck high (confirmed against the White Jet circuitry). I cut the output pin on the 7432 and was still stuck high and not pulsing away. Once swapped out with a replacement, The game is fully working again.

Schematics showing the area of the fault this time.

Atari Jet Fighter. PCB Repair.

Back in March I fired up my new cab and was pretty happy with the results, The game powered up and seemed to work, with exception of what I took as a graphic fault seen below where the Jets were displayed multiple times vertically down the screen. 

Original testing in March. 

I decided I was going to spend some time to look at this board this week just gone. My initial diagnosis above was not quite correct... Looking closer at what was on the screen the 'Jet' graphic was not complete and had bits missing especially noticeable in the white Jet. Also it was not possible to score points, I thought it may be due to the fact so many Jets were on screen at the same time. So I was looking at multiple faults already, and as (bad) luck would have it, after having the board on soak for a few hours I looked at the screen to check the game was still running and all I could see was a black screen! A few expletive's came out of my mouth and then I re-powered the cab, the image below is what I now had to work with...

The black 'Jet' and 'Score' were missing and instead of having a solid light background colour there we now horizontal bands in alternating colour going down the screen. (difficult to see in the photo below, but move visible in the photos further down.)

The fault log begins with this screen.

I have a copy of the Operation & Maintenance manual and it has some great description of what signals control certain aspects of the game, this certainly aided my fault finding, I also printed some A3 schematics that I could mark up in pencil and highlighter pens.

Initially I did go round the houses trying to work out where in the circuit the faults were, but after reading the manual a few times and following the signals in the schematics I got hot on the trail of issues, cutting to the chase, the faults were as follows.

IC location F3 a 74LS10 (3 input NAND gate) now had no output from pin 12. This provided the Jet/Score and Shell for black Jet.

Black Jet & Score back, but Jet video is inverted.

So with video back, I played a few games and noted that the score wouldn't increase when the Jets were hit with shells and the fact that no explosion registered to say the Jet had been hit. As it turns out another 74LS10 this time at location E1 had no Output on pins 6 & 8, these are the two trigger signals for Jet 1 & 2 respectively that further down the circuit chain pulse a 'BLO UP 1/2' signal which is used for detection of a hit. With this IC changed the score now worked and Jet explosions happened when hit by a shell.

Scores now working

The White Jet graphic was slightly corrupt not correctly displaying properly, The data for plane comes from ROMS at J5 & K6 (2K each). This data is shared between the two planes, so as the black Jet looked fine (although inverted) I was pretty sure the ROMs were OK. The ROM data is fed into a pair of Parallel to serial converters. For the white Jet they are at locations J4 & K4. Pin 7 of K4 provides the serial data through a few more IC's before becoming the Jet 2 video signal. The IC clearly was outputting something as you could see the image on screen, but my Logic probe was saying that pin 7 had no signal (High/Low or pulsing) Pin 9 is the inverted state id pin 7 and although not used in the circuit appeared dead too. I compared this to the Logic to the Black Jet and those same pins were pulsing along nicely. Time to swap K4, once replaced the Jet graphic was spot on and working.

I needed to get to the bottom of the 'multiple Jets on screen' fault that this board has had since I first turned it on. I'll put finding this fault down to mild guess work and lots of general probing around. I had the opinion that the issue was in the Vertical motion counter section of the circuit. Seeing as the fault was on both Jets and that each Jet had its own counter I had a hunch that these weren't directly the fault. The output from the counter for both Jets was fed into a 74LS74 flip flop IC. Pins 5 & 9 are the output pins which are mixed with the Horizontal blanking and Horizontal Jet position. They were stuck low. I cut one of the pins in circuit to confirm nothing else was pulling the pin low and it stayed low. Time to replace it...
Wohoo! Fixed as shown below, just the inverted black 'Jet' video and the background bars remaining.

Only one black Jet (Video inverted) and one white Jet.

More general probing around the final stages of video signals before they are joined in a resistor network found me this fault, IC at E4 an 74LS08 pin 6 provides the final video data for the White Jet. (Jet video and H/V blank info) As with the earlier fault the output was working but using a logic probe gave odd results, I did 'piggyback' an IC on top of the one in circuit and the background issue was gone, so I replaced the IC and that left the inverted video fault...

I remembered reading in the manual that when a Jet was hit by a shell the Jet's video was briefly inverted, to me it seemed this was happening constantly. The 'BLO UP' signal comes out or a 2 input gate at position K8, the logic probe was telling me this signal was constantly low, I monitored this in a game and made a white shell hit the black Jet, the output on the gate stayed low. Next up I cut this pin and re-powered the game. The Black Jets video image was now the correct was round, using the White Jet I fired a shell at the Black Jet, the game functioned as expected but without the brief inversion of video (that pin now wasn't connected!) So I replaced the IC and for now the game is fixed and fully working.

I've really enjoyed getting these faults fixed and think I've learnt a fair bit these last few evenings. Now its time to sort the cabinet out.

Cheers, Mart.

Background banding issue fixed, inverted Black Jet video fixed. Game...Fixed!

Atari Fire Truck. Board repair's...

If you were lucky enough to make it down to the South Coast Slam a few weekends back you might had seem and had a play on my FT cab. Unfortunately when I fired the cab up on the Saturday morning of the show, a graphic fault had developed on the Truck part of the vehicle. A quick re-seat of all socketed IC's didn't help the situation and the show went on and Fire Truck had a graphic fault as shown below. (Horizontal black lines running through what should have been the truck.)

Lines running through the truck graphics.

So it's time to get the schematics out and fix the issue, but first let me step back to the original fault when I turned the cab on after firing it up for the first time... See the image below, the game was not playable, the background was scrolling madly and a constant audio tone was coming out of the speakers.

Original board fault from September 2013

I sent the board to Andrew Welburn (P-Man) who fixed the game and sent through the following diagnosis along with the fully working board.

"

 > Your pcb is now fixed... brief fix summary : Address buffer at 1A had a couple of stuck 

 > bits and was replaced.. the cpu was dead as a doornail and was replaced, the zero page 

 > ram @ N2 was bad so it was replaced along with a socket install too. There was also a 

 > loose patch wire on H5 the graphics ram buffer that was rectified.

"

So where did I start with the current issue; Reading the Operation & Service manual confirmed that the tail cab data is stored in two ROMS at positions J5 & L5. These can be read as 2716 ROMS and in my programmer the checksums they gave matched the checksum I generated looking at the MAME rom file in a Hex Editior so these weren't the issue, and I must say I had a good look for dry solder joints before looking into component failure, my initial assumption was that the road journey to the show had caused some of the 35yr old solder to fail...

Fire Trucks Tail circuitry

So testing with my logic probe I confirmed the Address and Data lines were happily pulsing away, the data lines from the two ROMs pass through an LS273 at position M5, again the data was coming out of this pulsing away looking like what I think is OK. I did note that If I shorted and Input pin to Output pin (i.e. 2&3 or 4&5) It would create a similar fault to what I was already there but in a different position on the graphic. Next in line to check was an LS151 at M6 this is where all the ROM data is turned into a single output called TAILVIDEO. The select lines on this chip were pulsing away and none of the data inputs seemed bad so I was a bit stuck... 

Hoping for the day that I find a leg on a chip that is dead, stuck low or high, I decided to order an LS273 and an LS151 and try piggybacking them to see if the problem is fixed, first up I piggybacked the LS273 at M5 and it made no change to the fault. BUT I had more luck with the LS151 at M6. Boom upon piggybacking this chip the video fault had gone. YES! I removed the faulty chip, put in a new socket, inserted the chip and the fault was gone. I suspect that one of the Data bits of the LS151 was internally shorted.

It would have been nice to find the exact fault, but I'm happy it only took a few hours in total to get the cab running 100% again. Until the next time...

Fixed! :o)

New Cab. Midway Cruis'n World.

I had a new cab delivered yesterday for the UKVAC raid that was in Exeter in March. This is the photo of the cab at the Op's and It was unknown whether it would work or not. Most other cabs were working so I was pretty hopeful.

Cab at the Op's.

After having the cab delivered, I proceeded to take all the usual steps I do with a new cab. Look for any loose screws or washers that would short out PSU's etc, unplug the monitor and  unplug the game board. Once that was done I turned the cab on and check the PSU and monitor voltages. Every thing checked out out mains voltage in 110V on the Switcher and 240V on the monitor. The PSU has +5,+12 & -5Volt all sitting nicely.

It was also nice to bee greeted to some paperwork and a service manual in the back of the cab.

Paperwork in the back of the cab.

Next up was plugging the monitor power back in, I was expecting to this not to work as I discovered this sign attached to the monitor board.

Dead or Alive?

Expecting sparks to start flying or smoke I cautiously re-powered the cab and fortunately the monitor seemed to power up ok, I had neck glow and some light on the tube. Fingers crossed this was actually working.

Next up was plugging the game boar back in... I turned the cab on and shat myself as it gave a few loud audio beeps which made me jump! After 30 seconds or so I went round the front of the cab to see this...

Its Alive!

Holey Moley the game seems to work! I coined up and off I went of a world tour. The coin mech. even works fine. I adjusted the volume to a more sensible level for home use and wow that's it, a working cab. a few more photos of the cabs insides:

The picture on the monitor need some adjustment as to focus looks soft and the image is washed out, but overall this seems to be a solid cab, The game is just a bit poor...

I'm also very interested to see the sticker below attached to the cab. Made by SEGA? Quite fitting as I do intend to turn this into a multi driver SEGA cab. Once my other project are up and running. Cheers to Oll for organising the raid!

Made by Sega? Interesting.

01/05/14 UPDATE

To slightly update this post, it seems this cab is the same what Sega used for Scud Race cabs as can be seen in the below photo. It has different pedals and dash but other than the it looks the same profile to me.

The manual for the Cruis'n cab also has the seat (shown on the Scud Race) as an option. I'd really like to find one of those as the pedals do sit quite high.

South Coast Slam Photos

Yesterday I was at the South Coast Slam Pinball and Arcade event at Worthing, UK. I took my Fire Truck, Hang-On and Centipede along for the show and they all seemed popular throughout the day. There was an awesome selection or classic and rare machines along with tons of Pinballs that I know very little about :)

I only took a few (bad!) photos and a short video of Fire Truck being played. I was very happy with how much use Fire Truck got played, It had  over 500 credits put in on just the Saturday, and a whole range of young and old people were playing it.

My cabs being loaded on Friday morning.

Saturday before the show opened

Saturday before the show opened

Arcade section in full swing

Fire Truck being played by the brothers that inspired the start of restoration back on the UKVAC forum in early 2013. Cheers, Mart and Nick. Hope you had fun playing it!

Pinballs in action

More Pinballs

Atari Jet Fighter

I picked up a new cab today, Atari's 1975 Jet Fighter, this is a simple Black and White raster game and the game board is doesn't have a CPU, the whole game runs on TTL logic only like Pong and Breakout. This was bought as untested/unknown state and we're not talking eBay untested! This hadn't been switched on for a number of years so it was pot luck as to what would or wouldn't work.

Here's a few photos of the cab after I took it out of my car earlier today.

First impressions; Not bad at all for a 39yr old game, its a bit dusty, side art is still good and it is complete, monitor, game board, PSU all correct and present. Cab, Monitor and Game board all have matched, stamped serial numbers. This is Jet Fighter #1051.

So wanting to find out if it would work, I did some basic tests... game board and monitor connectors were removed. Mains input voltage was tapped correctly and proving 110V to the monitor plug and 36VAC to the game board.

I plugged up the monitor and wired a temporary connection of my signal generator, flicked the mains switch, a few seconds later I had neck glow an what sounded like high voltage on the screen, tentatively I looked at the screen and Yes! the monitor works.

  
Next up was plugging the game back in, I plugged the edge connector on and again flicked the power, this time I checked the voltage on the logic board before looking at the screen, the on-board AC to DC conversion was working nicely. Voltage on the logic IC's was bang on 5 volts.

So the game was displaying but the aeroplanes have a fault where they're duplicated across the whole screen. I coined the game up and both 'player' select buttons light up, and the game does play. All controls work and the 'fire' 'explosion' and 'plane' sounds work. The game finishes after a set time and that all works as it should.

The marquee light doesn't illuminate, not sure if its the tube or ballast I'll investigate that later.

I gave the plexi glass and monitor a good clean and this is who the image looks now.

A substantial difference to the brightness all thanks to some glass cleaner!

That's it for now I'll update this post when I decide how far I'm going to rework the cab and what I do to hopefully get it working.

Fire Truck. Racing to the Fire's

Well this is going to be the last update in the foreseeable future of my Fire Truck. It is now as complete and working as I want it to be, but there are a few items that I will come back to in the future when space and time permits. I would really like to remake the top cab panel and the two rear sections above and below the back door position. Theses parts are made of chipboard and have become slightly swollen, I'd like to replace them with MDF as I have with the new rear door and cover them in some black vinyl, similar to what was originally fitted. All the wooden edges would then line up and really top the cab off, but I'm restricted with space and now being winter I cannot work outside on the cab.

Anyway below is a photo of the rear cab with all the monitor wiring complete, I tapped the 240 volts for the monitor from one side of the interlock switches so it now essentially getting its power direct from the mains input when the interlock switches are closed and the cab is turned on.

After being happy with the cab innards, It was time to make a back door to replace the rotten one that came with the cab. It had a big section missing and was in a really poor state. The main door is a single piece of MDF cut to size, with a small section which holds it in place at the bottom.

Backdoor cut, lock hole drilled and edges sprayed

I was going to cover the door with some adhesive vinyl, but after seeing how the spray looked decided to cover the whole panel in spray and leave it at that for now. As you can see below the lock is fitted and the original Atari Information sheet was re-stapled to the inside of the door.

Backdoor complete

This next shot is a big of a tight angle but shows the door locked in place on the cab.

Backdoor fitted to cab

As mentioned above at some stage in the future I will replace the woodwork above and below the door along with the piece on the top of the cab.

The final piece of work needed to finish the cab off was to make a cardboard monitor surround. Even though my cab didn't have one, Phil who sold me the cab had one from the other Fire Truck cabs, so he lent it to me so I could make some replacements.

This was done using some heavy duty card from the Hobby Craft chain of shops and was carefully cut using multiple sharp blades, I disassembled the original monitor surround, drew round the pieces, cut them out and made the folds where necessary, finally I used hot melt glue to hold it all together.

Old bezel ready for templating

New pieces cut

Did I mention I made three of these today :)

My bezel, glued ready for fitting in the cab

New sticker with part Atari part number and a new custom revision.

In the cab. Nice!

Plexi glass installed, slight Vertical sizing adjustment need to be made.

Finally a few shots of the cab taken with a real digital camera and not my mobile phone.

Thanks for reading, and a bigger thanks go to Phil for letting me have one of the three cabs he picked up all those years ago.

FT-394 is ready to be played...

Enjoy, Mart.