Atari 600XL Capacitor Replacement Guide

Atari 600XL

This is the electrolytic capacitor list for the Atari 600XL. The 600XL is a single-board machine fed from an external +5 V DC supply, so there is no mains circuit inside it and no high-voltage electrolytics: every part below works on the 5 V rails or in the audio and video circuits.

Values, ratings and part numbers come from Atari's parts list in the 600XL Computer Field Service Manual; positions come from the schematic in the same manual. The list is for console assembly CA061614 and names no board revision or maker. The schematic draws the NTSC and PAL boards as one, with notes for the parts that differ on domestic units, and the manual warns that "minor variations in design may be encountered depending upon the production date of the console".

The supply

Atari's specification for the supply is "+5 VDC output (+/- 2%)", 1.5 A maximum, from 110 V AC; the supply is part CA061982 and the connector is a 7-pin DIN (J4) with +5 V on pins 1, 4 and 6. On the board the 5 V passes through the power switch SW1 and splits into three filtered rails, +5A, +5B and +5C, the names Atari's symptom checklist uses. There is no +12 V or −5 V rail and no voltage regulator in the 600XL.

Capacitor list

Atari 600XL electrolytic capacitors (FSM pp. 5-5 and 5-6)

Designator(s)	Value	Rating	Type	Atari part number	Where it is on Atari's schematic
C95, C96	470 µF	10 V	Aluminium electrolytic, axial	C014370	Input reservoirs after SW1: C95 on the branch that feeds +5A through L1, C96 on the branch that feeds +5B and +5C
C1, C6, C13, C64	22 µF	16 V	Aluminium electrolytic, axial	C014393	C1 beside C95; C6 beside C96; C13 on +5C after L10 and L3, the modulator supply; C64 on the +5 V feed to SIO pin 10, after ferrite bead L6
C44	47 µF	10 V	Aluminium electrolytic, axial	24-100476	Power-on reset timing: charged from +5A through R44 (56 kΩ), discharged through CR3, and squared up by U14 (74LS14) for the 6502's RESET input
C83, C101, C115	10 µF	16 V	Aluminium electrolytic	C014371	C83 on the +5 V to the controller jacks, after L8; C101 at the op-amp U8 input bias from +5B; C115 on the +5A feed through L14 (820 µH) to the video buffer U19
C100, C102, C103	4.7 µF	35 V	Non-polarised	C061647	Audio circuit around U8 (LM358), whose output goes to the RF modulator and the monitor socket: C100 couples the two op-amp stages, and C102 and C103 bring in the SIO and expansion-connector audio inputs

That is thirteen parts. Everything else on the board is ceramic: 0.1 µF (C014181-03), 0.001 µF (C014181-01), 0.01 µF (C014181-02), 0.047 µF (C014180-09) or a small value in picofarads. C100, C102 and C103 are non-polarised and need non-polarised replacements.

The Console5 Tech Wiki publishes community kit lists for two named 600XL boards, "NTSC Chelco Rev. 8A" and "PAL Rev A". They list a 22 µF electrolytic at C79 on the NTSC board and omit C96. Atari's parts list and schematic, which name no board, have C79 as a 0.01 µF ceramic in the keyboard scan circuit and C96 as the second 470 µF reservoir. The difference may be between boards; check what is fitted on your own board before ordering.

The 470 µF parts are rated 10 V in Atari's list. Replacements rated 16 V fit the same position.

Before you begin

Measure before replacing anything. For a black or grey screen Atari's symptom checklist starts with the +5 V from the supply and the +5A, +5B and +5C rails on the board, then the crystal Y1. On his Atari Projects site Jason Moore reports that the original electrolytics in Atari 8-bit computers do not fail often, though some do; look for discoloured, domed or leaking parts and replace those.

You will need:

• Temperature-controlled soldering iron, solder wick or a desoldering pump
• Leaded solder and 99 % isopropyl alcohol
• A multimeter; an ESR meter helps
• 105 °C electrolytics, the same capacitance and at least the original voltage rating; non-polarised parts for C100, C102 and C103

See Recommended Tools.

Disassembly

Atari's sequence:

1. Turn the unit upside down and remove four screws from the bottom cover.
2. Turn it upright and tip the cover by raising the left side to reach the keyboard cable. Remove the keyboard cable from its socket and lay the top aside.
3. With a magnetic screwdriver, remove the screw reached through the RF shield at the top left.
4. Remove the four remaining screws.
5. Lift out the PCB and RF shield together.
6. Remove the six bolts and nuts from the RF shield to separate it from the board.

Reassemble in reverse order.

Replacement procedure

1. Photograph the board first, and note the polarity of every polarised part against the board marking.
2. Desolder one lead at a time. The original capacitors are axial parts lying flat on the board, and the pads are small.
3. Clear the holes, clean the area with isopropyl alcohol and look for lifted pads or electrolyte damage.
4. Fit the new part with the positive lead to the pad marked "+". If a radial part replaces an axial one, dress the leads so the body cannot touch the RF shield.
5. Solder, trim, and inspect the joints under magnification.

Checking the result

1. With the machine unplugged, check there is no short between +5 V and ground.
2. Power up and measure +5 V at the CPU (U10) pin 8. On the 6502C, pin 8 is VCC and pins 1 and 21 are ground; pin 40 is RESET.
3. Check the rail at ANTIC (U9) pin 21, GTIA (U17) pin 27 and POKEY (U20) pin 17, the VCC pins in Atari's figures 1-4 to 1-6.
4. Hold OPTION while switching on, with no cartridge and no powered disk drive, and run the memory, audio-visual and keyboard tests.

If the machine misbehaves after a recap, check the new joints first, then whether a polarised part went into C100, C102 or C103.

Related pages

• Atari 600XL
• Atari 600XL General Maintenance
• Atari 600XL Troubleshooting Guide
• Atari 600XL Field Service Manual
• Atari 800XL Capacitor Replacement Guide
• Capacitor Failure Symptoms