Atari 600XL Capacitor Replacement Guide

This guide provides a complete electrolytic capacitor replacement reference for the Atari 600XL home computer. All electrolytic capacitors should be replaced as part of a preventive recapping to ensure continued reliability. The original capacitors are now over 40 years old and are prone to drying out, leaking, or losing capacitance, which can cause instability, audio issues, video distortion, and complete system failure.

Before You Begin

Tools Required

Temperature-controlled soldering iron (recommended 350°C / 660°F)
Solder wick (desoldering braid) and/or solder sucker
Fresh solder (60/40 or 63/37 leaded solder recommended for vintage PCBs)
Isopropyl alcohol (IPA, 99%) for cleaning
Multimeter with capacitance measurement capability
Magnifying glass or loupe for solder joint inspection
Anti-static wrist strap

Replacement Capacitor Recommendations

Use high-quality electrolytic capacitors from reputable manufacturers: Nichicon, Rubycon, Panasonic, or Elna.
Match or exceed the original voltage rating. Higher voltage ratings are acceptable and may improve longevity.
Match the original capacitance value. Do not use significantly higher capacitance values without understanding the circuit requirements.
For non-polarised (NP/bipolar) capacitors, ensure replacements are also non-polarised (bipolar) electrolytic types.
Use capacitors rated for 105°C operation where possible for improved lifespan.

Capacitor List — NTSC (Chelco Rev. 8A)

**NTSC Chelco Rev. 8A — Electrolytic Capacitor List**
Ref Des	Capacitance	Voltage	Type	Circuit Function
C1	22 µF	16V	Polarised electrolytic	Power supply decoupling / input filtering
C6	22 µF	16V	Polarised electrolytic	Power rail filtering near custom chips
C13	22 µF	16V	Polarised electrolytic	Power rail decoupling
C44	47 µF	10V	Polarised electrolytic	POKEY audio output coupling / power filtering
C64	22 µF	16V	Polarised electrolytic	Power rail decoupling near RAM
C79	22 µF	16V	Polarised electrolytic	Power rail filtering
C83	10 µF	16V	Polarised electrolytic	Signal coupling / filtering
C95	470 µF	16V	Polarised electrolytic	Main power supply bulk filter capacitor
C100	4.7 µF	35V	Non-polarised (NP/bipolar)	RF modulator / video output signal coupling
C101	10 µF	16V	Polarised electrolytic	Audio output stage filtering
C102	4.7 µF	35V	Non-polarised (NP/bipolar)	Video signal coupling (chroma/luma)
C103	4.7 µF	35V	Non-polarised (NP/bipolar)	Video signal coupling (composite output)
C115	10 µF	16V	Polarised electrolytic	Voltage regulator output filtering

Total: 13 electrolytic capacitors

Capacitor List — PAL (Rev A)

**PAL Rev A — Electrolytic Capacitor List**
Ref Des	Capacitance	Voltage	Type	Circuit Function
C1	22 µF	16V	Polarised electrolytic	Power supply decoupling / input filtering
C6	22 µF	16V	Polarised electrolytic	Power rail filtering near custom chips
C13	22 µF	16V	Polarised electrolytic	Power rail decoupling
C44	47 µF	10V	Polarised electrolytic	POKEY audio output coupling / power filtering
C64	22 µF	16V	Polarised electrolytic	Power rail decoupling near RAM
C83	10 µF	16V	Polarised electrolytic	Signal coupling / filtering
C95	470 µF	16V	Polarised electrolytic	Main power supply bulk filter capacitor
C100	4.7 µF	35V	Non-polarised (NP/bipolar)	RF modulator / video output signal coupling
C101	10 µF	16V	Polarised electrolytic	Audio output stage filtering
C102	4.7 µF	35V	Non-polarised (NP/bipolar)	Video signal coupling (chroma/luma)
C103	4.7 µF	35V	Non-polarised (NP/bipolar)	Video signal coupling (composite output)
C115	10 µF	16V	Polarised electrolytic	Voltage regulator output filtering

Total: 12 electrolytic capacitors (PAL Rev A lacks C79 compared to the NTSC Chelco Rev. 8A)

Differences Between Revisions

**Revision Differences**
Capacitor	NTSC Chelco Rev. 8A	PAL Rev A
C79 (22 µF / 16V)	Present	Absent
All others	Identical	Identical

Other board revisions (e.g., NTSC Rev D, Chelco Rev 3) may have additional differences. If your board revision is not listed here, visually inspect and document all electrolytic capacitors before ordering replacements.

Recapping Procedure

Step 1: Preparation

Power off the unit and disconnect all cables.
Remove the four screws from the bottom case (Phillips head).
Carefully separate the top and bottom case halves.
Disconnect the keyboard ribbon cable from the motherboard.
Remove the motherboard mounting screws and lift the board free of the case.
Photograph the board to document the original capacitor locations and orientations.

Step 2: Capacitor Removal

Identify each capacitor by its reference designator (printed on the PCB next to the component).
Note the polarity orientation of each capacitor before removal — the negative stripe on the capacitor body should align with the PCB markings.
Apply the soldering iron to one pad at a time while gently pulling the capacitor from the opposite side.
Use solder wick or a solder sucker to remove excess solder from the through-holes.
Clean the pad area with IPA to remove any flux residue or electrolyte leakage.

Step 3: Capacitor Installation

Insert the new capacitor into the correct position, observing the correct polarity (positive lead to the "+" marked pad).
For axial capacitors, ensure the leads are properly aligned with the pad spacing.
Solder each lead with a clean, shiny joint. Avoid excessive heat — hold the iron to the pad for no more than 3 seconds.
Trim excess leads flush with the solder joint.
Visually inspect each joint for cold solder (dull, grainy appearance) or solder bridges.

Step 4: Post-Recapping Verification

Visual inspection: Check all solder joints under magnification for cold joints, bridges, or lifted pads.
Continuity test: Verify there are no short circuits between +5V and GND using a multimeter in continuity mode.
Power-on test: Connect the power supply and verify the system boots normally.
Voltage verification: Measure +5V at the CPU (pin 40 of U1) to confirm the power rail is clean and within spec.
Audio test: Run the built-in self-test (hold OPTION during power-on) and verify the POKEY audio test produces clean tones.
Video test: Check for clean, stable video output with correct colours.

Critical Capacitors

C95 — Main Bulk Filter (470 µF / 16V)

This is the most critical capacitor on the board. It filters the incoming +5V supply, smoothing out ripple and providing current reserve for transient loads. A failed C95 will cause:

Voltage sag under load, leading to random crashes
Increased ripple on the +5V rail, causing video noise (horizontal lines or "jail bars")
System failing to boot entirely if the capacitor is shorted

Replacement recommendation: Use a 470 µF, 25V (or higher) capacitor rated for 105°C and low ESR.

C100, C102, C103 — Non-Polarised Video Coupling (4.7 µF / 35V NP)

These three non-polarised (bipolar) electrolytic capacitors are in the video output signal path. Failed capacitors here cause:

Loss of colour output (black and white image)
Weak or washed-out video
No composite or RF video output

Important: These must be replaced with non-polarised (bipolar) electrolytic capacitors, not standard polarised types. Using polarised capacitors in these positions will result in degraded video quality and premature failure.

C44 — POKEY Audio Coupling (47 µF / 10V)

This capacitor is associated with the POKEY chip's audio output. A failed C44 causes:

No audio output or very quiet audio
Distorted or "buzzy" sound
Clicking or popping from the speaker/audio output

Pre-Made Cap Kits

Pre-assembled capacitor kits for the Atari 600XL / 800XL are available from specialist suppliers such as Console5. These kits contain all necessary electrolytic capacitors pre-sorted by reference designator, using high-quality Nichicon, Rubycon, or Panasonic components.

When ordering, specify your board revision (NTSC Chelco Rev. 8A, PAL Rev A, etc.) to ensure the correct parts are included.

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