Editing Commodore VIC-20 Capacitor Replacement Guide

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'''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 only has a single logic / power-supply board – there is no separate analogue board – so the tables below are everything you need.

=== 🖥️ Early 2-Prong Board (Assy 324003 & “214003”) ===
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''Early VIC-20 Capacitors'''
! Board Ref !! Capacitance !! Voltage !! Purpose (rail / circuit)
|-
| C10 || 100 µF || 16 V || 9 VAC ► +5 V pre-reg filter&#8203;:contentReference[oaicite:0]{index=0}
|-
| C11 || 4 700 µF || 10 V || Main +5 V bulk filter&#8203;:contentReference[oaicite:1]{index=1}
|-
| C12 || 220 µF || 25 V || +12 V line for VIC analogue core&#8203;:contentReference[oaicite:2]{index=2}
|-
| C13 || 1 000 µF || 16 V || Secondary +5 V smoothing (regulator out)&#8203;:contentReference[oaicite:3]{index=3}
|-
| C18 || 10 µF || 16 V || Power-on reset RC timer&#8203;:contentReference[oaicite:4]{index=4}
|-
| C90 || 3.3 µF || 50 V || Audio-path coupling (VIC DAC)&#8203;:contentReference[oaicite:5]{index=5}
|-
| C91 || 470 µF || 10 V || Datasette motor supply filter&#8203;:contentReference[oaicite:6]{index=6}
|}

*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) ===
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''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 ==
{| class="wikitable styled-table" style="width:75%; text-align:center;"
|+'''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.

== 🔗 Related Pages ==
* [[Commodore VIC-20 General Maintenance Guide]]  
* [[Commodore VIC-20 Troubleshooting Guide]]  
* [[CRT Discharge Procedure]]

[[Category:Commodore Systems]]
[[Category:Commodore Maintenance Guides]]
[[Category:Capacitor Replacement Guides]]