Recap guide

Recap the Commodore 64 and 64C

Board electrolytics are often fine, but a recap is common preventive care. The power brick is potted and is usually replaced instead.

Open the interactive checklist Tick off each capacitor as you replace it. It saves in your browser.

Check first. A recap is not always the answer here, so look at the guides before you order parts.

Which board do I have?

Boards changed during production. These notes come from the linked sources, and many are only partly documented, so check the board in front of you.

• C64 assy 326298 (silver label) (Medium confidence). How to tell: Earliest breadbin board with 5 pin A/V output (c64-wiki); revisions 6, A, B, C. Capacitors: A shop kit for this board has 18 electrolytics plus a ceramic restore key; individual values not shown. Capacitor list differs from other revisions: yes. Source
• C64 assy 250407 (Medium confidence). How to tell: 1983 breadbin; revisions A to C; 8 pin video; common board. Capacitors: Not itemised in sources read. Capacitor list differs from other revisions: not known. Source
• C64 assy 250425 (long board) (Low confidence). How to tell: 1984 board with single 8701 clock IC; a comment says rev B has an extra disc cap next to C15 beside the 6569. Capacitors: A cap mod guide uses this board; sellers list sets for it but without values. Capacitor list differs from other revisions: not known. Source
• C64C assy 250466 (Medium confidence). How to tell: Early C64C with two 64Kx4 RAM chips and horizontal fuse behind the cartridge port. Capacitors: No cap list found. Capacitor list differs from other revisions: not known. Source
• C64C assy 250469 (rev 1, 3, 4, A, B) (Medium confidence). How to tell: Short board, vertical fuse, 64 pin custom chip. Capacitors: Power section differs: single 5V rail, and SID 9V and 12V made by a transistor circuit, so regulator related caps differ from older boards. Capacitor list differs from other revisions: yes. Source

Where to start

Clues from write-ups and forum threads, not a diagnosis. Low confidence means one thread or one repair; high means several write-ups agree.

• Ripple on the 5V rail (Low confidence). One write-up explains why old caps with high ripple matter, and describes ripple on the 5V line killing chips. It has no parts list. Source
• Parts choices (Low confidence). An element14 video page offers a partial bill of materials with polymer and ceramic choices. Source

Tips, tales and maybes

Found in write-ups and forum threads. These are other people's reports, not tested by us. Check part references and values against your own board.

• Watch out: Regulator failure sends too much 5V (Medium confidence). The C64 wiki says the main danger of old bricks is over-voltage on the 5V line that destroys the computer. It documents only the screwed-together 902503-02, lists regulator options 3052P, NTE1934 and LM2596, and a 4700uF 16V cap, with an electrocution warning for the mains terminals. Source
• Tip: Cracked regulator joints and mild undervoltage (Medium confidence). A PSU test write-up says cracked solder joints on the regulators from thermal cycling are a recurring fault, and a unit sagging to 4.6-4.7V under load may not show symptoms until it fails. It adds that cheap switch-mode replacements can inject noise into video and audio on some C64 boards. Source
• Tip: 9V line dropping points at the transformer (Low confidence). On the MIDIbox forum a poster says the most reported brick fault is the 9V line falling to 3-4V while 5V holds, which indicates a short in the transformer coils. Potted units are described as not serviceable, and aged diode rectifiers can raise the voltage delivered to the computer. Source
• Story: Recap improved a grainy picture (Low confidence). A 250407 board restoration reports that replacing the electrolytics on the main board and RF modulator, watching polarity, improved a grainy washed-out picture, though the VIC-II stayed soft. The same job swapped MT-branded RAM for another make and added heatsinks. Source

Before you start

• Boards changed during production. Check your board number against the guides before you order parts.
• A mains power supply can hold a dangerous charge. If you are not trained to work on one, have a professional do it.

Manuals and technical documents

Service manuals, schematics and datasheets for this machine, kept in our own library. Check your own board and part numbers against them.

• Commodore 64 Service Manual, C64 - C64C, March, 1992, PN-314001-03 (Service manual)

All 1 documents for Commodore 64 and 64C in the library

Circuits 1

Circuits we redrew in one plain style, with the parts listed. Our own drawing from the source diagram, so check it against the original before you build anything.

Guides we used

This page and the interactive bench are built from these. They have the photos and the full detail, so please read them and support their authors.

• Capacitor Replacement on a Commodore 64 - WorkBench Wednesdays 04 (Video) by James Lewis (Bald Engineer), element14. Has a capacitor list. Video page with a bill of materials (polymer and ceramic choices); described as a partial list
• Mark Sawicki - C64c repair (Video) by Mark Sawicki (CommodoreInfoPage on YouTube), listed on Commodore News. News listing embedding the video: replaces electrolytics and regulators on a C64C
• RetroManCave - C64 repair (Video) by RetroManCave (YouTube), listed on Commodore News. C64C repair that includes replacing electrolytics, adding heatsinks
• Commodore 64 Repair (Write-up) by tfw8b. Explains why old caps (high ripple) matter; no parts list

C64 assy 326298 (silver label)

Eighteen electrolytics. There is also a small ceramic at C38 (51 pF) that Console5 swaps for 4.7 nF to bring back the soft-touch RESTORE key. Console5 notes many C64s shipped with 50 V parts in the regulator section, while its kits use 25 V as later schematics call for.

C64 assy 250407

The C88 value changed between revisions (470 uF on rev B and earlier, 1000 uF on rev C and later), and Console5 says one 1000 uF part works for all of them. C12 is an electrolytic on rev B but may be ceramic on other revisions. C38 (51 pF ceramic) is swapped for 4.7 nF to restore the soft-touch RESTORE key.

C64 assy 250425 (long board)

Six electrolytics. C38 (51 pF ceramic) is swapped for 4.7 nF to restore the soft-touch RESTORE key. Console5 shows a 25 V part at C90 even though the schematic says 50 V.

C64C assy 250466

Seven electrolytics. C38 (51 pF ceramic) is swapped for 4.7 nF to restore the soft-touch RESTORE key.

C64C assy 250469 and 252311

Nine capacitors on the short C64C board.

C64 modulator, Commodore 250469

Console5 lists these by value, not by reference number. Its universal C64 modulator kit covers every modulator listed here.

C64 modulator, Commodore 326130-01 / C-MOD REV-6 51A1-2

Two matching parts.

C64 modulator, Commodore 51A1-10 REV-2

Listed by value, not by reference number.

C64 modulator, Mitsumi MD6-UE3603

Listed by value, not by reference number.

C64 modulator, Mitsumi MD6-VA3402

Two capacitors.

C64 modulator, Mitsumi MD6-VA3403

Two capacitors.

C64 modulator, Mitsumi MD6-VA3405

Three capacitors.

Shopping list

77 capacitors in all, grouped by value. Buy a few spares.

• 32 x 10 µF, 25 V (check your board): Amazon · eBay
• 7 x 100 µF, 16 V (check your board): Amazon · eBay
• 6 x 10 µF, 16 V (check your board): Amazon · eBay
• 6 x 470 µF, 25 V (check your board): Amazon · eBay
• 4 x 1000 µF, 25 V (check your board): Amazon · eBay
• 4 x 2200 µF, 16 V (check your board): Amazon · eBay
• 2 x 2.2 µF, 50 V (check your board): Amazon · eBay
• 2 x 4.7 µF, 16 V (check your board): Amazon · eBay
• 2 x 22 µF, 25 V (check your board): Amazon · eBay
• 2 x 220 µF, 16 V (check your board): Amazon · eBay
• 2 x 330 µF, 10 V (check your board): Amazon · eBay
• 1 x 1 µF, 50 V (check your board): Amazon · eBay
• 1 x 4.7 µF, 25 V (check your board): Amazon · eBay
• 1 x 47 µF, 16 V (check your board): Amazon · eBay
• 1 x 100 µF, 10 V (check your board): Amazon · eBay
• 1 x 220 µF, 25 V (check your board): Amazon · eBay
• 1 x 220 µF, 10 V (check your board): Amazon · eBay
• 1 x 470 µF, 10 V (check your board): Amazon · eBay
• 1 x 470 µF, 6.3 V (check your board): Amazon · eBay

Console5 capacitor kits for this machine

Console5 sells ready-made capacitor kits. Kits come in different versions, so match the board number in the kit name to yours and check the listing before you buy.

• Commodore 64 C64 Cap Kit A Assy 326298
• Commodore 64 C64 Cap Kit B Assy 250407
• Commodore 64 C64 Cap Kit C Assy 250425 250466
• Commodore 64 C64C Cap Kit D Assy 250469 252311
• Commodore 64 C64 C64C Modulator Cap Kit Universal

Skip the sourcing

• Ready-made kit: Amazon · eBay
• Already recapped: Amazon · eBay

While you are in there

• Need the machine itself?: Amazon · eBay
• A box of spare capacitors: Amazon · eBay

Affiliate links. As an Amazon Associate I earn from qualifying purchases. These links only search by name. Disclosure

Step by step

1. Photograph both sides of the board before you touch anything. Zoom in on every capacitor. The photo is your map when you are three hours in.
2. Unplug it, take out the batteries and let it sit. Old power supplies and CRT parts can hold a charge. If your machine has a tube, leave the tube and its board to a professional.
3. Open it up and keep the screws sorted. A muffin tin or an egg carton works. Different screws go in different holes, and the holes never forgive you.
4. Look for leaks. Clean any sticky residue off with isopropyl alcohol and a soft brush. A leaked capacitor leaves brown crust and can eat copper traces. Look at the traces under it, not only the part itself.
5. Mark the polarity of every capacitor on the photo before it comes off. On an electrolytic, the stripe marks the negative leg. The board usually shows a half-shaded circle or a bar for the same spot.
6. Remove the old capacitors one at a time. Surface mount: add fresh solder to both ends and rock the part off, or use flux and a low-melt alloy. Through-hole: heat one leg at a time and clear the hole with wick or a pump.
7. Clean the pads and check for lifted pads or damaged traces. Clean flux off with isopropyl. A bad pad needs a jumper wire, not hope.
8. Fit and solder the new capacitor, matching polarity. Same capacity, same or higher voltage, and it has to physically fit. Work from the smallest parts up.
9. Clean the flux off and look at every joint. A good joint is shiny and shaped like a tiny volcano. A dull blob or a ball is a cold joint: reflow it.
10. With a multimeter, check for shorts across the power rails before you power it on. Use the continuity or resistance setting. A reading near zero means stop and look for a solder bridge.
11. Power it up and test everything: video, sound, controls, the lot. If something is wrong, check polarity first. It is the most common mistake and the easiest fix.

Tools

• Temperature-controlled soldering station. Steady heat so you do not cook pads. Most recaps are done between 320 and 350 C. Top: Hakko FX-951 · Mid: Hakko FX-888D · Budget: Pinecil
• Good solder. Rosin-core 63/37 flows and looks right. It is cheap and it matters. Kester 44 63/37
• Flux. Flux is what makes old joints let go and new joints flow. MG Chemicals flux pen · Chip Quik flux syringe
• Low-melt alloy (for surface mount). Melts old solder on both ends of a surface mount part at once, so it lifts off cleanly. Chip Quik SMD1
• Desoldering tool. Clears the old solder out of through-hole pads. Top: Hakko FR-301 · Mid: Engineer SS-02 pump · Budget: Solder wick
• Fine tweezers. For holding small surface mount parts exactly where you want them. ESD-safe tweezers
• Board holder. A third hand for the board, so both of yours are free. PanaVise circuit board holder
• Magnification. You cannot fix what you cannot see. Surface mount parts are tiny. Top: Stereo microscope · Mid: Head visor · Budget: Lighted magnifier
• Multimeter. Continuity, shorts and rail voltages. The one test that saves boards. Top: Fluke 117 · Mid: Fluke 101 · Budget: AstroAI
• ESR and capacitor tester. Checks old capacitors and your new ones before they go in. Top: Peak Atlas ESR70 · Budget: LCR-T7
• Isopropyl alcohol (99%) and a brush. For cleaning leaked goo and flux. Use the high-percentage kind. MG Chemicals 99.9% isopropyl
• Brass tip cleaner. A clean tip transfers heat. A dirty one does not. Hakko 599B
• Fume extractor. Pulls the smoke away from your face. Hakko FA-400 · Budget: Small bench fan
• Precision screwdrivers. Most old gear uses a mix of Phillips, Torx and security bits. iFixit Pro Tech Toolkit
• Kapton tape. Heat-proof tape to protect parts that sit close to the one you are changing. Kapton tape

Safety

• Good airflow, or a fume fan. Solder smoke is not for breathing.
• Safety glasses on. Solder spits and clipped legs fly.
• Iron in its stand when you are not holding it. Know where the cord is.
• Touch bare metal first, or use a wrist strap. Static kills old chips.
• No tube, no mains power supply. Leave those to a professional.
• Wash your hands after, especially if you used leaded solder.

Values are shown as published in the guides above, and boards changed during production. Check the board in front of you. A recap involves hot tools and, on some machines, dangerous voltages. You do it at your own risk.

More

• All recap guides
• The interactive Recap Bench
• Fix a dead vintage computer
• Commodore 64 on the timeline
• Commodore 64C on the timeline