Editing Commodore 64C Capacitor Replacement Guide

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Replacing the electrolytic capacitors (recapping) in your '''Commodore 64C''' is a vital preventative measure to ensure stable operation, clear video and audio output, and long-term reliability. As these components age, they can cause erratic behaviour, power instability, video artefacts, and leackage. Recapping your 64C restores original performance and protects the chips from power-related faults.

== Visual Inspection & Failure Signs ==

Before recapping, examine all electrolytic capacitors for these common failure indicators:

* '''Bulging or domed tops''' – Indicates internal gas pressure and imminent failure.
* '''Leaking electrolyte''' – Brown, green, or white residue at the base of the capacitor.
* '''Corrosion or PCB staining''' – Green/black marks or discolouration around pads.
* '''Unusual behaviour''' – Audio hum, video glitches, or random resets can often be traced to failing capacitors.

If any capacitor shows signs of distress, it is strongly recommended to replace '''all''' electrolytic capacitors on the board.

== Commodore 64C Capacitor List ==

The Commodore 64C (board Assy 250469 and variants) uses a revised, cost-reduced PCB with fewer and smaller electrolytic capacitors compared to earlier C64 models. Always cross-check values with your board’s silkscreen, as minor revisions exist.

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{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''Commodore 64C (Assy 250469) Electrolytic Capacitors'''
! Ref !! Capacitance !! Voltage !! Circuit / Rail !! Notes
|-
| C88 || 2,200 µF || 10 V || Main +5 V bulk || Main filter for logic supply
|-
| C89 || 1,000 µF || 10 V || VIC-II local decoupling || Sits near video chip (8565/8562)
|-
| C90 || 330 µF || 10 V || SID 8580 analogue +9 V || Audio rail filter
|-
| C91 || – || – || – || Not fitted (12 V rail deleted)
|-
| C15 || 10 µF || 16 V || Reset RC timer || Ensures reliable power-on reset
|-
| C38 || 47 µF || 16 V || Audio DC block || Lower value for 8580 SID bias
|-
| C70 || 2.2 µF || 50 V || Chroma coupling (RF modulator) || Small foil can, optional if modulator removed
|-
| C71, C72 || 47 µF || 16 V || RF modulator 5 V/audio buffer || Two cans inside modulator can
|}

''If your board is a rare 250469-Aldi variant with a 6581 SID, it may include C92 (470 µF, 16 V) for a linear 12 V regulator. Replace this if present.''

=== SMD Capacitors ===
The standard 64C PCB does '''not''' use SMD electrolytics; all are through-hole types. If you encounter SMD cans, your board may be a late third-party or repair replacement—verify values before ordering.

== Capacitor Replacement Procedure ==

# '''Disassemble the C64C''' – Remove case screws (three at rear, two under keyboard), gently lift the keyboard, and unplug the LED and keyboard connectors.
# '''Remove the RF shield''' – Desolder or carefully unclip the folded metal tabs. Set aside for reassembly.
# '''Document capacitor positions''' – Take photos or label wires if unsure.
# '''Desolder old capacitors''' – Use solder wick and flux. Commodore used high-melting-point solder; set your iron to at least '''375 °C'''. Be patient with ground planes.
# '''Clean pads''' – Remove any residual solder and clean with isopropyl alcohol.
# '''Install new capacitors''' – Match polarity (long lead = positive) and ensure correct lead spacing (5 mm or 7.5 mm). Keep capacitor height below 17 mm for shield clearance.
# '''Inspect work''' – Check for solder bridges or cold joints.
# '''Reassemble and test''' – Refit the shield, reconnect keyboard and LED, and close the case.

== Recommended Tools & Parts ==

* '''Temperature-controlled soldering iron''' (70 W, 2 mm chisel tip)
* '''Solder wick and desoldering pump'''
* '''Leaded 63/37 or quality lead-free solder'''
* '''105 °C, low-ESR radial capacitors''' (brands: Nichicon PW/PS, Panasonic FR/FC, Rubycon ZLH)
* '''Isopropyl alcohol (IPA) and nylon brush'''
* '''Kapton tape''' (to insulate capacitors near the RF shield)
* '''Multimeter''' (for continuity and voltage checks)
* '''Protective eyewear'''

== Post-Recap Voltage & Ripple Checks ==

After recapping, verify the main power rails with a multimeter or oscilloscope:

{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''Commodore 64C Power Rails (No Cartridge, BASIC READY)'''
! Test Point !! Expected Voltage !! Max Ripple (p-p)
|-
| +5 V (PLA pin 24) || 4.95 – 5.10 V || < 50 mV
|-
| +9 V (SID 8580 pin 28) || 8.7 – 9.3 V || < 100 mV
|-
| 9 VAC (user port pins 10/11) || 8.5 – 10 V rms || Sine-like
|}

''If you observe video shimmer, audio buzz, or random resets, recheck your soldering and capacitor polarity. Ripple above 100 mV on any rail indicates a possible fault.''

== Additional Tips ==

* '''Test your power supply first''' – A faulty “brick” can destroy new capacitors and chips.
* '''Keep capacitor diameter similar''' – Especially for C89 and C90, as the RF shield may press against them.
* '''RF modulator removal''' – If you have performed a composite/S-video mod and removed the RF modulator, C70, C71, and C72 may be omitted.
* '''Reseat socketed chips''' – After recapping, temperature changes may unseat the VIC-II, SID, or PLA.
* '''Store your C64C in a dry environment''' – Moisture accelerates capacitor degradation.
* '''Dispose of old capacitors responsibly''' – Use an electronics recycling facility.

== Related Pages ==
* [[Commodore 64C Troubleshooting Guide]]
* [[Commodore 64 Power-Supply Protector (C64 Saver)]]
* [[Commodore 64 Video Output Upgrades]]

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