Atari 800 Capacitor Replacement Guide

Recapping your Atari 800 is essential for reliable operation, stable video, and protection of irreplaceable custom chips. After four decades, the original aluminium electrolytic capacitors are prone to drying out, leaking, or failing open—leading to random crashes, distorted audio, power instability, or even permanent board damage. Proactive replacement of these components restores performance and extends the life of your classic Atari.

Visual Inspection & Failure Signs

Before recapping, carefully examine all electrolytic capacitors for:

Bulging or domed tops – Indicates internal gas build-up and imminent failure.
Leaking electrolyte – Brown, black, or green residue at the base or on the PCB.
Corrosion or PCB staining – Discolouration or green/white crust around capacitor leads.
Unusual odours – A fishy or acrid smell often signals capacitor leakage.
System symptoms – Random lockups, video flicker, audio hum, or power-on issues.

If any capacitor shows signs of failure, replace all electrolytics on the mainboard and power supply for best results.

Atari 800 Capacitor List

The Atari 800 uses only through-hole electrolytic capacitors on its mainboard and power supply board. SMD electrolytics are not present. Always double-check values and polarity before replacement, as minor revisions exist.

Mainboard Electrolytic Capacitors

**Atari 800 Mainboard Electrolytic Capacitors**
Ref. Designator	Capacitance	Voltage	Function / Notes
C56	2200 µF	16 V	Main +5 V filter (bulk smoothing)
C57	470 µF	16 V	+12 V rail filter (regulator output)
C58	47 µF	16 V	+5 V local decoupling (CPU/ANTIC)
C59	10 µF	16 V	Reset circuit timing
C60	10 µF	16 V	Audio path (DC-blocking)
C61	4.7 µF	25 V	Video output coupling
C62	1 µF	50 V	Colour circuit coupling
C63	10 µF	16 V	Power-on reset filter
C64	100 µF	16 V	+5 V local decoupling (GTIA/POKEY)
C65	47 µF	16 V	+12 V local decoupling

Some late-production boards may have minor value changes; always match what is fitted.

Internal Power Supply Board Capacitors

The Atari 800’s internal power supply (not the external “brick”) contains additional electrolytics:

**Atari 800 Power Supply Board Electrolytic Capacitors**
Ref. Designator	Capacitance	Voltage	Function / Notes
C1	4700 µF	25 V	Main DC reservoir (after rectifier)
C2	220 µF	25 V	+12 V regulator input filter
C3	220 µF	16 V	+5 V regulator input filter
C4	10 µF	25 V	Regulator output decoupling

If your 800 has a third-party or repaired PSU, values may differ—replace like-for-like.

Recapping Procedure

Unplug all power and peripherals. Remove the top cover and keyboard.
Remove the RF shield (desolder or carefully unbend tabs).
Label and disconnect all internal cables (keyboard, power, video).
Desolder each capacitor using braid or a pump. Atari used robust, high-temperature solder; set iron to 370–380 °C.
Clean pads with isopropyl alcohol and inspect for lifted traces or corrosion.
Install new capacitors, matching polarity and lead spacing (most are 5 mm or 7.5 mm).
Trim leads and solder, ensuring shiny, solid joints.
Reassemble and double-check all connectors before applying power.

Recommended Tools & Parts

Temperature-controlled soldering iron (2 mm chisel tip)
Desoldering braid and/or spring pump
Leaded 63/37 or quality lead-free solder
105 °C, low-ESR radial electrolytic capacitors (Nichicon PW/PS, Panasonic FR/FC, Rubycon ZL/ZLH)
Isopropyl alcohol (IPA) and antistatic brush
Kapton tape (to insulate capacitors near shielding)
Multimeter (for continuity and voltage checks)
ESD wrist strap (recommended)

Post-Recap Voltage & Ripple Check

After reassembly, verify all voltage rails under load (computer powered, BASIC READY):

**Atari 800 Voltage Rails (measured at mainboard test points)**
Test Point	Expected Voltage	Max Ripple (p-p)
+5 V (CPU, ANTIC, GTIA)	4.90 – 5.15 V	< 50 mV
+12 V (POKEY, audio, video)	11.5 – 12.5 V	< 100 mV
+9 V (unregulated, after rectifier)	8.5 – 10.5 V	sine-like

Excessive ripple or voltages out of range may indicate a failing external PSU or regulator fault.

Extra Tips

Test the external PSU first – Overvoltage or AC ripple can destroy new capacitors and custom chips.
Observe polarity carefully – Atari silkscreen markings are not always clear; double-check before soldering.
Use quality capacitors – Cheap generics often fail early; use reputable brands.
Clean any leaked electrolyte thoroughly – It is corrosive and can damage traces.
Inspect for previous repairs – If you find bodged or missing parts, consult the schematic before proceeding.
Retain original lead dress – Keep replacement capacitors close to the board to avoid RF shield contact.
Re-seat socketed chips after recapping – Power cycling can unseat them.

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