Commodore VIC-20 Capacitor Replacement Guide

Replacing electrolytic capacitors (“recapping”) in a Commodore VIC-20 is one of the highest-impact reliability upgrades you can perform. A fresh capacitor set restores clean DC rails, reduces video noise, cures random resets, and protects rare MOS chips from over-ripple voltage spikes.

Visual Inspection & Failure Signs

Bulging tops – Any domed aluminium case is a near-certain failure.
Electrolyte residue – Brown crust or oily film at the capacitor base.
ESR drift – Even if a cap looks fine, elevated ESR (> 2 Ω on small signal caps, > 0.2 Ω on main filters) is enough to destabilise the 5 V rail.
Heat-darkened PCB – Large cans (C11/C13) often cook the FR-4 underneath; that heat ages surrounding parts as well.

If any of the above are present – or if the machine is 40 years old and un-serviced – replace the full set.

VIC-20 Logic-Board Capacitor Lists (by Assy #)

The VIC-20 has a single logic board the tables below contain all the replaceable capacitors.

Early 2-Prong Board (Assy 324003 & “214003”)

**Early VIC-20 Capacitors**
Board Ref	Capacitance	Voltage	Purpose (rail / circuit)
C10	100 µF	16 V	9 VAC ► +5 V pre-reg filter
C11	4 700 µF	10 V	Main +5 V bulk filter
C12	220 µF	25 V	+12 V line for VIC analogue core
C13	1 000 µF	16 V	Secondary +5 V smoothing (regulator out)
C18	10 µF	16 V	Power-on reset RC timer
C90	3.3 µF	50 V	Audio-path coupling (VIC DAC)
C91	470 µF	10 V	Datasette motor supply filter

Values mirror Commodore service-manual BOM; some very early 1981 PCBs mark C10/C12 as 35 V parts – 25 V or 35 V replacements are both acceptable.

Cost-Reduced “VIC-20 CR” Board (Assy 250403)

**Cost-Reduced VIC-20 Capacitors**
Typical Ref	Capacitance	Voltage	Notes
C1	22 µF	25 V	Reset / audio decouple (moved by layout change)
C2	10 µF	50 V	Cassette sense filter
C4	1 000 µF	16 V	Bulk +5 V – external PSU now supplies DC directly
C6	470 µF	10 V	9 VAC► +12 V doubler filter (VIC & cassette motor)
C7	100 µF	16 V	VIC chroma/luma decouple (near RF modulator)
C8	220 µF	25 V	+12 V rail post-rectifier filter

> Board markings vary. Commodore deleted the on-board 7805 on Assy 250403, so the 4 700 µF can is absent; the largest can you will see is 1 000 µF. Always cross-check against your board silkscreen before ordering.

Recapping Procedure

Disassemble – Remove six case screws, slide keyboard forward, lift the RF shield.
Label cables – Photos help when reconnecting the power-LED & keyboard flex.
Desolder caps cleanly using a temperature-controlled iron & braid / pump; apply gentle upward pressure only after all solder is molten to avoid lifting pads (VIC-20 traces are thin).
Install new capacitors – observe polarity: the striped/- side to ground. Lead-spacing on main filters is 5 mm; modern 8 mm diameter caps fit without bending.
Inspect & wash – Flux residue is mildly conductive; scrub with 99 % IPA and a soft brush.
Re-form (optional) – Bring the board up on a bench supply through a 1 Ω resistor for the first 30 s to reform large cans gently.

Post-Recap Voltage Checks

**Expected Rails (No-Cartridge, BASIC Prompt)**
Test Point	Early 324003	CR 250403	Notes
+5 V (6502 pin 40)	4.95 – 5.10 V	4.95 – 5.10 V	Regulator (early) vs external PSU
+12 V (VIC pin 28)	11.6 – 12.6 V	11.6 – 12.6 V	Derived from 9 VAC doubler
9 VAC (cassette port pin 4)	8.5 – 10.0 V AC	same	Drives tape motor & 12 V doubler

An oscilloscope should show < 50 mV p-p ripple on +5 V after recap.

Recommended Tools & Parts

60 W temperature-controlled iron (fine conical tip)
Desolder‐pump and braid – VIC pads lift easily if overheated.
ESR-meter (handy to confirm big cans).
Leaded 63/37 Sn-Pb solder (melts ~183 °C – safer for old FR-4).
Radial 105 °C capacitors from Nichicon, Panasonic FR/FC, Rubycon ZLJ or equivalent.
Small flush-cutters, IPA, ESD wrist-strap.

💡 Extra Tips

Socket clean-up: while the board is open, reseat the VIC, CPU & VIA ICs – oxidation here causes more faults than bad caps.
Regulator upgrade (early board): consider replacing the TO-220 7805 with a modern drop-in switching regulator to cut internal heat by ~8 °C.
Composite-mod recap: if you’ve removed the RF modulator in favour of direct composite, you can omit its two 100 µF caps – they only filter the RF can’s internal 5 V line.
Cap spacing: Commodore often bent electrolytic leads outward – clip the old leads flush and use the holes; don’t enlarge them with a drill, the inner-layer vias run very close.
Stagger your install: replace and test in sections (power, then audio/video). If something suddenly fails you’ll know which group to re-check.