Recap guide

Recap the Sega Master System

A modest cap count. SMS II recaps are common during RGB and regulator refreshes, but we found no documented failure epidemic. One write-up lists values for an early PAL SMS II board.

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.

• Mark III 171-5304 (Japan, 1985-1987) (Medium confidence). How to tell: Original Japanese console with the expansion port on the left and a built-in card slot; only one board revision. Capacitors: No capacitor information found. Capacitor list differs from other revisions: not known. Source
• 171-5379 / 837-6067 (NTSC SMS1, 1986-1987; also France) (Medium confidence). How to tell: First NTSC revision with double-sided plated-through solder joints and a Sony V7040 video encoder. Capacitors: ConsoleMods' board page lists 29 capacitors: electrolytics from 10 to 180 uF at 10V or 16V plus film or ceramic parts; mounting style is not stated. Capacitor list differs from other revisions: not known. Source
• 171-5532 / 837-6405 (NTSC SMS1, 1988) (Medium confidence). How to tell: Cost-reduced board with single-sided solder joints and a CXA1145 encoder. Capacitors: No cap list found. Capacitor list differs from other revisions: not known. Source
• 837-6629 and 837-6700 (NTSC SMS1, 1988-1992) (Medium confidence). How to tell: Later NTSC boards; 837-6700 adds the 315-5330 logic array and one 32 KB PSRAM for video. Capacitors: No cap list found. Capacitor list differs from other revisions: not known. Source
• PAL SMS1 171-5385, 171-5534 VA1, 171-5672 VA2, 171-5535-10 VA3 (Medium confidence). How to tell: 171-5385 hides its clock circuit under a soldered shield, VA1 uses rubber dome switches, VA2 adds a reverse-polarity diode, and VA3 is a major redesign with a 4-pin oscillator. Capacitors: No cap list found. Capacitor list differs from other revisions: not known. Source
• Master System II 171-5922A (early PAL, 1990-1991) (Medium confidence). How to tell: Initial PAL SMS2 board introduced in Australasia in late 1990 and Europe in 1991, marked 171-5922-A. Capacitors: A Retro Repairs log lists 15 through-hole electrolytics (six 10uF 16V CE positions, C18 10uF 16V, C31 1uF 50V, C32 10uF 16V, C38, C41, C42, C43 100uF 16V, C44 47uF 10V, C54 10uF 16V) and says SMS2 variants have different cap values and locations; ConsoleMods lists 26 capacitor entries for the same board. Capacitor list differs from other revisions: yes. Source
• Master System II later boards (M4Jr VA1, 171-6395A PAL 2M, 171-6416A 2M) (Medium confidence). How to tell: M4Jr VA1 has the built-in Alex Kidd, while 171-6395A and 171-6416A carry a 2-megabit BIOS with built-in Sonic. Capacitors: No cap list found. Capacitor list differs from other revisions: not known. Source
• Master System III Compact (Brazil) (Low confidence). How to tell: Brazilian compact model, mix of through-hole and SMD parts. Capacitors: ConsoleMods says it mixes through-hole and SMD components; no values given. Capacitor list differs from other revisions: not known. Source

Where to start

We did not find a clear list of what fails first on this machine, so we are not guessing. Read the guides below, check the board for leaks, and replace what you can see.

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: Polarity and silkscreen errors (Medium confidence). A restoration write-up on an SMS II (PAL 171-5922-A, 15 electrolytics) warns that wrongly oriented electrolytics run hot and can burst, and that the board silkscreen sometimes has factory orientation errors. It advises replacing one cap at a time and taking photos of the original first. Source
• Tip: High heat for the modulator and DIN (Medium confidence). The same write-up says the original RF modulator and DIN connector need a high-power iron to remove and refit because of their thermal mass. It also recommends a thorough isopropyl clean after the work. Source

Before you start

• Boards changed during production. Check your board number against the guides before you order parts.

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.

• Sega Master System II Service Manual, April, 1991 (Service manual)
• Sega Master System Service Manual (Service manual)
• Sega SC-3000 Service Manual (Service manual)

All 3 documents for Sega Master System 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.

• 1992 SEGA Master System II restoration and modification (Write-up) by Adam Wilson (Retro Repairs & Refurbs). Has a capacitor list. Per-position values for an early PAL 171-5922-A board. Site states all rights reserved, so link only
• Master System II refurbishment (Write-up) by hitmanmcc. Recap plus 7805 swap on an RGB-modded unit; no values or board number
• Mark III refurbishment (Write-up) by hitmanmcc. Recap and 7805 on a 171-5904 board; no values

Master System 837-6067 (M4 Power Base, NTSC; also 171-5378)

Sixteen capacitors. Console5 says the 171-5378 uses this same list. It also notes that this board only works with the v1.3 BIOS, in case you are fitting a replacement.

Master System 837-6405 / 171-5532 and 837-6629 (M4 Power Base, NTSC)

Fifteen capacitors.

Japanese Master System 837-6148 (IC board M4J main)

Console5 calls this revision an outlier, with a very different capacitor selection from all the other Master Systems. Twenty-three capacitors.

Master System II 837-7275 (IC board M4Jr VA1)

Console5 found six capacitors marked CE on this board.

Master System II 837-7275 (IC board M4Jr VA1 RGB)

Console5 says some versions have an RF modulator and some have a DIN8 AV jack.

Master System II PAL 171-5922A (IC board M4Jr PAL)

This list comes from the service manual, and Console5 says the CE and CP capacitors are probably not numbered on the board.

Master System II PAL 171-6395A (IC board M4Jr PAL 2M)

Console5 found six capacitors marked CE on this board.

Master System Power Base PAL VA3

Console5 says up to six capacitors marked CE may be found on VA3 boards.

Power Base Converter / Mega Adaptor

Three capacitors. Console5 thinks the 1 uF part at C4 is on the Power Base Converter only.

Sega Mark III main board 171-5304

Eighteen capacitors. The Mark III has its own list, close to the Master System ones but not the same.

Sega Mark III My Card board 171-5305

One capacitor.

Sega SG-1000 main board

Six capacitors. Console5 lists them without a board revision.

Shopping list

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

• 57 x 10 µF, 16 V (check your board): Amazon · eBay
• 33 x 100 µF, 10 V (check your board): Amazon · eBay
• 18 x 47 µF, 10 V (check your board): Amazon · eBay
• 13 x 1 µF, 50 V (check your board): Amazon · eBay
• 10 x 100 µF, 16 V (check your board): Amazon · eBay
• 7 x 2.2 µF, 50 V (check your board): Amazon · eBay
• 6 x 10 µF, 10 V (check your board): Amazon · eBay
• 5 x 47 µF, 16 V (check your board): Amazon · eBay
• 1 x 220 µF, 10 V (check your board): Amazon · eBay
• 1 x 330 µF, 16 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.

• Sega Master System Cap Kit
• Japanese Sega Master System Cap Kit For 837 6148 Revision Sms
• Power Base Converter Mega Adaptor Master System Converter II Cap Kit
• Sega Mark III Cap Kit Mark 3
• Sega Sg 1000 Cap Kit SG1000

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
• Sega Mark III (Japan) on the timeline
• Sega Master System II on the timeline
• SG-1000 on the timeline