Jet Fighter *ATARI anno 1975* *Restoration*

[Thzarr]

Jet Fighter
Atari Arcade


Anno 1975


Info: 
http://www.arcade-museum.com/game_detail.php?game_id=8232
Download  Jetfigher Service Manual incl schematics etc.
http://www.arcade-museum.com/manuals-videogames/J/JetFighter.pdf

The 19" B/W CRT service manual -  pm me


I have this arcade standing in my livingroom. Sorry, I have to say its not in mint condition

[PL1]

Welcome aboard, Thzarr.

Are you planning on doing a full or partial restoration?


Scott

[Thzarr]

Short Briefing:

At startup, you directly hear engine and blast sounds coming from the speakers.
Actually its starting right in a ongoing game. Weird.
When the game is over, its enter attract mode, and the speakers are silenced.
But the two startbuttons backlighting, its on. ready for a new game.
And no coin have been inserted.  the coin counter is to hot to touch.
Its being feed by constant voltage insted of pulse to activate the coincounter.
Something is very wrong.

According to the manual a normal startup should be directly in attract mode and no sound at all.
Only when you start a game the sound starts.

***************

A loose connector cause a burned gnd edge contact. I solder the gnd cable to the PSU caps gnd.

The Game.
2 player.
White plane=1st player
Black plane= "Computer" or 2nd player.

The White plane could only turn right and fire w/ sound and explosion but no visible missile.
You have no chance to win the game.

[Thzarr]

pics

[ChadTower]

I would start by verifying the voltages both at the beginning near the power supply inputs and at the end of processing.  Sadly, debugging this game is probably going to be a game of TTL cat and mouse.  Fortunately those TTL chips can usually be tested by themselves using a DMM. 

[Thzarr]

Near the input: ~4.78vdc  ->  4.7vdc around the chips. 
All the switches got 4.75vdc except Coin and Slow" switch,  only 3,6vdc. 

Changed bypass cap 220u to 820u,  but that didnt boost the supply.

[ChadTower]

I'm betting that is too low.  Try backing up to the transformer and work your way forward.


And check that edge connector again.  If it's burned off at the ground contacts the repair might not have been good enough.

[Thzarr]

Its all in the jet fighter manual, detailed description.
I read it backwards and sideways trying to follow the path of starting process.

Sadly, Its not in original condition anymore. I cut the two main caps 2x8000uf and replaced it with a RIFA 10.000uf. Hoping it could be power failure.  No change.

[Thzarr]

Long story short:
The first chip that activates the coincounter and startup procedure is located at F8.
With a wire I  poked at F8 inputs/output to fake HIGH or LOW signals to affect other chips.

GND-> F8 pin 1,2,3,4,5,6  (1,3) (2,4) (6)  Turned on the start buttons
Vcc .> F8 pins. -"-  Turned off the start buttons.

The low voltage on the coin switch got me thinking, its must be a short somewhere.
Where do the coinswitches get its voltage from, I couldn't find it.

1.st player joystick switches exl Fire and Right were failing.

I changed 100nf Y5V ceramics to 10uf elyt.
Still the same.

[Thzarr]