Atari 130XE Controller Port Repair

The two 9-pin controller ports on the right-hand side of a PAL 130XE, marked 1 and 2 on the case

The two controller ports of the Atari 130XE are 9-pin D connectors on the right-hand side of the case; Sams' board drawing marks J6 as port 1 and J5 as port 2. On Atari's schematic the four joystick directions of each port come from port A of the PIA (U23) through 220 Ω resistors and 10 µH filter inductors, the paddle (pot) lines go to POKEY (U22) through 1.8 kΩ resistors, and the two fire buttons go to the GTIA (U17). Sams' service data gives a BASIC test program for each kind of controller and the chip pin that each function uses, so a dead direction or button can be followed from the port to the chip.

Symptoms

• A joystick direction does not work in one port.
• A joystick fire button does not work.
• A paddle does not turn the reading, or its button does not work.

Try a known-good controller in the port before opening the computer.

Safety

Pins 7 and 8 of each port carry +5 V and ground from the board. Do not short them while probing a powered port.

Tools and parts

• A logic probe, an oscilloscope and a meter.
• A known-good joystick and, for the pot lines, a paddle controller.
• Replacement parts as found: 220 Ω resistors (R120 to R127), 1.8 kΩ resistors (R76 to R79), 9-pin D connectors for J5 and J6 (Atari C019062).

Procedure

Test with a joystick

Plug a joystick into the port under test and run Sams' program.

10 PRINT ,"JOYSTICK","BUTTON"
20 FOR P=0 TO 1
30 PRINT "PORT";P+1,STICK(P),STRIG(P)
40 NEXT P
50 FOR T=1 TO 200:NEXT T
60 GOTO 10

The number under BUTTON should change from 1 to 0 while the button is pressed. The number under JOYSTICK reads 15 at rest and should change to 14 for up, 13 for down, 11 for left and 7 for right.

Follow a dead joystick function

The PIA U23 on Atari's schematic: PA0 to PA3 (pins 2 to 5) go to J6 pins 1 to 4, and PA4 to PA7 (pins 6 to 9) to J5 pins 1 to 4, each through a 220 Ω resistor and a 10 µH inductor

1. Find the chip pin for the dead function in the table below and put the logic probe on it. The reading should go from high to low when the function is used.
2. If the reading is correct, the fault is in the chip: check the GTIA (U17) for a button, or the PIA (U23) for a direction.
3. If the reading is not correct, check the parts connected to that pin and the connections at J5 or J6. On Atari's schematic each direction line runs from the PIA through a 220 Ω resistor (R120 to R127) and a 10 µH inductor to the port, with a 0.001 µF capacitor to ground.

Joystick functions and chip pins (Sams CC16)

Function	Port 1	Port 2	Port pin
Up	U23 pin 2	U23 pin 6	1
Down	U23 pin 3	U23 pin 7	2
Left	U23 pin 4	U23 pin 8	3
Right	U23 pin 5	U23 pin 9	4
Button	U17 pin 8	U17 pin 9	6

Test with paddles

POKEY's pot inputs P0 to P3 (pins 14, 15, 12 and 13) through 1.8 kΩ resistors and 10 µH inductors to pins 9 and 5 of the two ports

Run Sams' paddle program.

10 PRINT ,"PADDLE","BUTTON"
20 FOR P=0 TO 3
30 PRINT "PADDLE";P,PADDLE(P),PTRIG(P)
40 NEXT P
50 FOR T=1 TO 200:NEXT T
60 PRINT:GOTO 10

The number under PADDLE should vary from 228 to 1 as the paddle is turned from minimum to maximum, and the number under BUTTON should change from 1 to 0 when the button is pressed.

Paddle lines and chip pins (Sams CC16)

Port	Paddle	POKEY (U22) pin	Button	PIA (U23) pin
1	0	14	0	4
1	1	15	1	5
2	2	12	2	8
2	3	13	3	9

Follow a dead paddle function

1. For a paddle that does not change, look at its POKEY pin with the oscilloscope while turning the paddle. The waveform should change from a sawtooth (Sams' figure 2) to a pulse (figure 3) across the travel.
2. If the waveform is missing, check the port connector and the paddle, then try another POKEY.
3. For a paddle button that does not work, put the logic probe on its PIA pin. It should go from high to low when the button is pressed. If it does not, check the button switch and the port connector; if it does, try another PIA (U23).

Repair

1. Open the machine: remove the four screws from the bottom of the case, lift the top and disconnect the keyboard cable, then remove the seven board screws and lift out the board and shield.
2. Resolder cracked joints at J5 and J6, and replace an open resistor or inductor in the failing line.
3. Refit the shield, the board and the top.

Testing

Run both programs again and work each direction, button and paddle in each port. If the production test cartridge and its player-port loop-back plugs are available, the ports test should report PASS; error 37 points at the lines from the PIA to the connectors, 38 at the pot lines and POKEY, and 39 at the trigger lines and GTIA.

Related pages

• Atari 130XE
• Atari 130XE Troubleshooting Guide
• Atari 130XE SIO Port Repair
• Atari 800XL Controller Port Repair
• Sams Computerfacts Atari 130XE
• Atari 130XE Parts List and Production Test Instructions