Sega Dreamcast VMU Maintenance
Routine maintenance for the Sega Dreamcast VMU: its cells, opening the case, the battery terminals, the buttons, the connector and the saves held in flash. The VMU runs from two CR2032 lithium cells when it is used on its own and from the Dreamcast's 5 V supply when it is in a controller. There is no mains or high voltage anywhere in it.[1][2]
Before starting
[edit | edit source]Copy any saves you want to keep to a second memory card first. On the Dreamcast, select the file in the file menu, choose "Copy", pick the destination card and choose "Start Copying". Files shown in red are copy-protected and cannot be copied.[3] Changing the cells does not touch the flash, so saves survive a cell change.[4]
Cells
[edit | edit source]The VMU takes two CR2032 lithium coin cells under a cover on the back, held by one screw.[5] Sega's instructions for changing them:[6]
- Fit two new CR2032 cells of the same make together. Do not pair a new cell with a used one.
- Check the polarity of each cell as it goes in.
- Expect the clock to be reset. Set the date and time again, from the VMU or from the Dreamcast.[7]
The cells are needed only for standalone use: running mini-games, managing files and keeping the clock. In a controller the VMU is powered by the Dreamcast and saves and loads without cells, but a VMU with no battery power sounds its buzzer when the Dreamcast is switched on.[4][8]
How long cells last
[edit | edit source]| Use | Figure |
|---|---|
| Clock only, new cells | About 130 days, from the VMU's instruction manual[9] |
| A program running standalone, LCD on, no sound, no transfers or flash writes | About one week (VMU Specifications); about two weeks (Hardware Manual)[6][4] |
Screen updates use five times the power of reading flash, and flash writes 25 times; copying files between two VMUs uses a great deal.[6] When the cells are close to the end of their life the BIOS powers the VMU down, even in the middle of a game.[4]
A VMU in file or clock mode goes to sleep after about two minutes with no button press and no communication.[10] Sega Retro notes that a VMU left in a controller runs on its own cells after the Dreamcast is switched off, until it powers itself down.[11]
Leaked or corroded contacts
[edit | edit source]Take the cells out of a VMU that is going into storage for a long time. If a cell has leaked, clean the terminals and the board around them before fitting new cells; see Battery Explosion, Capacitor or Corrosion Damage.
Opening the case
[edit | edit source]iFixit's teardown takes the VMU apart in four steps:[5]
- Remove the silver screw from the battery cover and take out both cells.
- Remove the four black screws from the back. Lift the rear case gently: the piezo buzzer is glued inside it and wired to the board. Peel the buzzer off the case with a spudger if the case has to come away completely.
- Remove the two screws holding the battery terminals to the board.
- Lift the board out of the front case. The LCD comes off the board, and the screen stay, D-pad and rubber button mat lift out of the front case.
On reassembly, screw both battery terminals down firmly. GameTechWiki found that a VMU whose terminal blades were not tight against the board after it had been opened would not power up.[12] The board is marked BLADE-A and BLADE-B where the two terminals fit.[13]
Buttons
[edit | edit source]
The buttons are a rubber mat pressing on gold interdigitated pads on the front of the board, labelled UP, DOWN, L, R, A, B, SUS and MODE.[13] If a button needs a hard press or works only intermittently, clean its pad and the conductive face of the rubber with isopropyl alcohol on a lint-free swab, let them dry and reassemble. The reset button on the back resets everything except the flash memory and the clock.[10][14]
Connector
[edit | edit source]The 14-pin connector carries the serial lines and power to the controller or to a second VMU.[1] Keep the cap on when the VMU is not in a controller.[14] Inspect the contacts for bent pins and dirt, and clean them with isopropyl alcohol. Sega's Dreamcast manual says to switch the VMU to clock or file mode before plugging it into a controller, because it may malfunction in other modes.[3]
Flash memory
[edit | edit source]The 128 KB of flash keeps saves with no power at all.[4][8] If the Dreamcast can no longer use a card, initialise it from the file menu: select the ALL icon, then "Delete All (Memory Reset)". This erases every file. While it runs, do not unplug the controller, do not plug or unplug memory cards, and do not switch off the Dreamcast.[3] Homebrew tools that unlock 44 extra blocks can leave a card that some games, among them Metropolis Street Racer, do not detect.[8]
External power
[edit | edit source]GameTechWiki's modification powers a VMU from 6 V DC soldered to the battery terminals, from four alkaline cells or an adapter of at least about 340 mA. The large blade is negative and the small blade positive. A working VMU beeps as soon as power is applied, without a button press.[12]
Checks after maintenance
[edit | edit source]| Check | Expected |
|---|---|
| Fresh cells fitted | A beep as power arrives[12]; the clock asks to be set[6] |
| Left untouched in file or clock mode | Sleeps after about two minutes; the SLEEP button wakes it[10] |
| Plugged into a controller on a running Dreamcast | Listed on the memory card selection screen with its free blocks[3] |
| Current drawn from the cells | Sega's battery-life method uses 0.610 mA running on the quartz clock, 2.600 mA on the RC oscillator and 0.060 mA asleep[9] |
Related pages
[edit | edit source]- Sega Dreamcast VMU
- Sega Dreamcast VMU Troubleshooting Guide
- Sega Dreamcast VMU Capacitor Replacement Guide
- Sega Dreamcast VMU Documentation
- Sega Dreamcast Maintenance Guide
- Battery Explosion, Capacitor or Corrosion Damage
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 Sega Enterprises, Ltd., Visual Memory Unit (VMU) Hardware Manual, p. VMD-2, Table 2.1 (PDF p. 170 of File:Sega Dreamcast VMU Developer Documentation.pdf): CR2032 × 2; external input +5 V and +3.3 V; 14-pin connector carrying the serial interface and power.
- ↑ Sega Enterprises, Ltd., Dreamcast VMU Specifications, p. VMU-4, Figure 1.4 "Block Diagram (preliminary)" (PDF p. 144 of File:Sega Dreamcast VMU Developer Documentation.pdf): cells and +5 V through a selector and DC/DC converter to +3.5 V.
- ↑ 3.0 3.1 3.2 3.3 Sega, Dreamcast instruction manual (US, 2000), p. 16 "Managing game files", p. 17 "Selecting a file" (green: VMU executable files; red: copy-protected files; black: saved game files), pp. 18-19 "Initializing a memory card" and p. 20 "Copying files". Scanned at archive.org.
- ↑ 4.0 4.1 4.2 4.3 4.4 Sega Enterprises, Ltd., VMU Hardware Manual, pp. VMD-24 and VMD-25, "Batteries" (PDF pp. 192-193 of File:Sega Dreamcast VMU Developer Documentation.pdf).
- ↑ 5.0 5.1 iFixit, "Dreamcast VMU Teardown", guide 82677, retrieved 2026-10-19. Step 1: remove the silver screw and the batteries. Step 2: remove the four black screws; take care with the speaker wire and peel the speaker from the shell with a spudger. Step 3: remove the two battery terminal screws. Step 4: lift the main board out, take the screen off the board, and remove the screen stay, D-pad and rubber buttons from the shell.
- ↑ 6.0 6.1 6.2 6.3 Sega Enterprises, Ltd., Dreamcast VMU Specifications, p. VMU-20, "Batteries" (PDF p. 160 of File:Sega Dreamcast VMU Developer Documentation.pdf): fit two brand new CR2032 cells made by the same manufacturer; check the polarity; the clock settings are initialised; files in flash are kept.
- ↑ Sega Enterprises, Ltd., Visual Memory System Hardware Manual, Revision 1.00 (1998), section 1.8 "Clock Function": the clock can be set on the VMU's own setting screen or from the Dreamcast. Text copy at archive.org.
- ↑ 8.0 8.1 8.2 Wikipedia, "VMU", retrieved 2026-10-19. Two CR2032 cells under a screw-secured lid; without battery power the VMU still works as a memory card and auxiliary display but beeps when the Dreamcast is powered on.
- ↑ 9.0 9.1 Sega Enterprises, Ltd., VMU Hardware Manual, "Calculation of Battery Life", pp. VMD-223 to VMD-226 (PDF pp. 391-394 of File:Sega Dreamcast VMU Developer Documentation.pdf): about 130 days for the clock alone on new lithium cells (quoted from the VMU instruction manual); CR2032 210 mAh, 82 % (174 mAh) usable; quartz oscillator 0.610 mA, RC oscillator 2.600 mA, sleep 0.060 mA.
- ↑ 10.0 10.1 10.2 Sega Enterprises, Ltd., VMU Hardware Manual, pp. VMD-22 and VMD-23, "Sleep Function" and "Buttons" (PDF pp. 190-191 of File:Sega Dreamcast VMU Developer Documentation.pdf): sleep after the SLEEP button, auto power-off, or no button press or communication for about 2 minutes; only the SLEEP button wakes it; the reset button resets everything except the flash memory and the clock.
- ↑ Sega Retro, "Visual Memory Unit", retrieved 2026-10-19. VMUs keep running on their own power for a short time after the console is switched off, and VMUs without power screech when the console starts.
- ↑ 12.0 12.1 12.2 GameTechWiki, "VMU Power Supply Mod", retrieved 2026-10-19. 6 V DC at the battery terminals; an adapter of at least about 340 mA; the large blade is negative and the small blade positive; a working VMU beeps as soon as it receives power; loose terminal blades after opening, or part-drained cells, stop it powering up.
- ↑ 13.0 13.1 GameTechWiki, "VMU", retrieved 2026-10-19, board photographs hosted here as File:Sega Dreamcast VMU board front.jpg and File:Sega Dreamcast VMU board rear.jpg.
- ↑ 14.0 14.1 Sega Enterprises, Ltd., Dreamcast VMU Specifications, p. VMU-3, Figure 1.3 "External Appearance and configuration (preliminary)" (PDF p. 143 of File:Sega Dreamcast VMU Developer Documentation.pdf): the cap over the communication connectors.