Mattel Aquarius General Maintenance
Care, opening and routine checks for the Mattel Aquarius. The Aquarius has no battery and no moving parts apart from the keyboard and switches. Its power comes from an external plug-in transformer on a captive cord, and everything inside the case runs from low-voltage DC.[1][2]
The Aquarius at a glance
[edit | edit source]| Part | Detail |
|---|---|
| Power supply | Plug-in transformer on a cord fixed to the case; +8.8 V, +16 V and −19 V DC on a four-pin connector inside[2][1] |
| Regulation | 7805 for +5 V, fixed to the RF shield; transistor regulator for +12 V[3][4] |
| Electrolytic capacitors | Eight on the main board, the largest 10,000 µF 16 V and 1,000 µF 25 V[5] |
| Keyboard | Rubber keys; 16-conductor flat cable pushed into a slot on the board[2][6] |
| RF shield | Metal cover over most of the board, soldered in places as well as held by twisted tabs[2][6] |
| Ports | Cartridge port, printer jack, cassette DIN socket, TV output[1] |
Before you start
[edit | edit source]- Unplug the transformer from the wall before opening the case. The transformer is the only part that carries mains voltage.[1]
- The 10,000 µF capacitor on the 8.8 V line stores enough charge to keep the power light lit for about ten seconds after switch-off. Let it discharge, or discharge it through a resistor, before working on the board.[6]
- The keyboard cable is the part most easily damaged when opening the case. Read Opening the case first.[2]
Opening the case
[edit | edit source]- Turn the computer over and remove the six screws in the bottom case.[2]
- Lift the halves apart slowly. The keyboard stays in the top half and the main board in the bottom half, joined by the flat keyboard cable.[2]
- The keyboard cable is about 3 inches (75 mm) long, made of clear plastic with 16 printed conductors, and comes away only at the main board end, where it is held in a slot by friction. Pull it straight out of the slot, holding the cable at its end. It tears and creases easily, and pushing it back into the slot is awkward with so little slack.[2]
- The power cord cannot be pulled out of the case. Inside, it ends in a four-pin in-line connector on pins at the back of the board. To free it, push the curved plastic tab beside the pins away from the connector and lift the connector off.[2]
- Harrington's video Motherboard Removal shows the whole board, shield and cord coming out as one assembly.[7]
Removing the RF shield
[edit | edit source]Most of the board is under a metal shield that is soldered to the board in several places as well as twist-locked. Desolder the soldered points with a desoldering iron or pump and untwist the tabs. Leaded Solder tore a corner pad when one shield pin did not come free, so make sure each joint is clear before lifting.[6][8] The RF modulator has its own can, held by twisted and soldered tabs to the ground areas of the board; it does not need to come off for ordinary maintenance.[6][2]
Care and handling
[edit | edit source]Radofin's guide gives these rules for the case and ports:[9]
- Stand the Aquarius on a flat, firm surface so that the air vents in the bottom work, and not on carpet.
- Keep fingers out of the cartridge port and the open ends of cartridges.
- Fit the cartridge port dust cover whenever no cartridge or expander is in the port.
- Do not lift the computer by its cables, by the Mini Expander or by the hand controllers.
The keyboard assembly stays in the top case behind a metal plate held by a row of small screws; the flat cable leaves it at the back.[10]
Power cord and transformer
[edit | edit source]The transformer's outputs are +8.8 V at 1.2 A, +16 V at 0.15 A and −19 V at 0.01 A, on red and black, yellow and black, and blue and black wires. Viewed from the back of the computer, the four wires on the board connector are, left to right, yellow, black, red and blue.[2] Leaded Solder describes the outputs as "presumably unregulated".[6]
Because the cord is fixed to the case, a damaged cord or transformer cannot simply be swapped. The FAQ suggests making a test supply from the transformer and cord of a scrapped Aquarius: cut the cord inside the dead machine, keep its four-pin connector, and rejoin connector and cord, so that the supply can be plugged onto the board of a machine under test with the case left part open.[2] Harrington made a supply for an Aquarius II, which arrived without one, by modifying a donor supply from an original Aquarius.[11]
Regulator heat
[edit | edit source]The 7805 that makes the +5 V rail is fixed to the RF shield, which acts as its heatsink.[4] It drops the 8.8 V input to 5 V and turns the difference into heat; Leaded Solder notes that these regulators "generate a lot of heat".[3][6] Two owners have replaced it with a pin-compatible switching regulator to run the machine cooler:
- Harrington fitted a Murata OKI-78SR-5/1.5-W36H-C (5 V, 1.5 A), which no longer needs to be fixed to the shield.[5][4]
- Leaded Solder fitted a Traco TSR 1-2450, soldered into the original holes, and notes the higher switching noise as the trade-off.[6]
Either is optional; Leaded Solder thought his original regulator "probably fine".[6] If the original stays, make sure it is screwed firmly to the shield when the machine is reassembled.
TV output
[edit | edit source]NTSC machines have a recessed channel 3/4 selector on the back. Set it with a small screwdriver or the tip of a ballpoint pen to whichever channel has the weaker broadcast signal in your area, and set the television to the same channel.[1] Radofin's machines for other countries were built for one channel only (UHF channel 36 in the UK, for example), or with a switch between two VHF channels.[9]
The RF picture is poor on modern sets. Harrington's open-source composite AV adapter replaces the RF modulator and gives composite video and audio on a 3.5 mm jack; it needs a +5 V jumper wire from the main board, because +5 V is not present at the modulator position.[6]
Capacitors
[edit | edit source]The board has eight electrolytic capacitors, five of them in the power section.[5] They are over forty years old and Harrington recommends replacing them; the list, positions and procedure are on the Mattel Aquarius Capacitor Replacement Guide.
Storage
[edit | edit source]Radofin's guide asks owners to protect the computer and cartridges from excessive heat, to keep it away from heating and air-conditioning outlets, and to switch it off and disconnect it from the mains when not in use.[9] Fit the cartridge port cover before storing it.[9]
Preventive maintenance checklist
[edit | edit source]- Inspect the power cord and transformer for damage before plugging in.[2]
- Check that the power light comes on and the start-up screen appears; see the Mattel Aquarius Troubleshooting Guide if not.[1]
- Keep the cartridge port covered when unused.[9]
- If the case is opened, check that the keyboard cable is fully home and not creased, and that the 7805 is screwed to the shield.[2][4]
- Replace the electrolytic capacitors once, following the Mattel Aquarius Capacitor Replacement Guide.[5]
Related pages
[edit | edit source]- Mattel Aquarius
- Mattel Aquarius Troubleshooting Guide
- Mattel Aquarius Capacitor Replacement Guide
- Mattel Aquarius Mini-Expander
- Mattel Aquarius Documentation
- Capacitor Failure Symptoms
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Mattel Electronics, Aquarius Home Computer System Simplified Instruction Cards, 5931-0250-G3 (1982), hosted here as File:Aquarius Simplified Instruction Cards.pdf: card 3 (PDF p. 4), the back panel and the power cord ending in a plug-in transformer; card 5 (PDF p. 6), set the TV to channel 3 or 4, whichever has the weaker signal, and the computer's selector to the same channel with a small screwdriver or ballpoint pen tip; card 15 (PDF p. 16), troubleshooting tips.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 Fred Horvat and Gil Parrish, "Mattel Aquarius FAQ", last updated 6 May 2001 (retrieved 2026-10-19). "What's the Power Supply?": external transformer, not designed to be removable; +8.8 V 1.2 A (red-black), +16 V 0.15 A (yellow-black), −19 V 0.01 A (blue-black); four-pin connector inside that locks against a curved plastic piece; wire order from the back yellow, black, red, blue; making a movable test supply from a scrapped unit. "What's Inside the Aquarius?": six screws in the bottom; the keyboard cable, clear plastic with 16 conductors, about 3 inches long, removable only at the motherboard, held by friction, easy to tear or bend and awkward to reinsert; most components under a soldered metal shield; RF modulator with its own cover.
- ↑ 3.0 3.1 Sean P. Harrington and Mack Wharton, Aquarius Motherboard v1-1-0 Rev D schematic, 30 April 2022, hosted here as File:Aquarius Motherboard v1-1-0 Rev D Schematic.pdf, power system: U10 7805 for +5 V; Q4 with ZD1 for +12 V.
- ↑ 4.0 4.1 4.2 4.3 Aquarius+ (Sean Harrington), "Aquarius Computer - Installing a Replacement Power Regulator", YouTube, 20 September 2019, description (read 2026-10-19): the OKI-78SR-5 "runs cooler and is not tethered to the RF/Heat Shield of the case anymore"; Murata Power Solutions switching regulator, 5 V DC output, 1.5 A.
- ↑ 5.0 5.1 5.2 5.3 Sean P. Harrington, "Capacitor Replacement", Get Your 8-Bit On! (retrieved 2026-10-19): the electrolytics are over 40 years old and replacement is recommended; about 16 components in the power circuitry, five of them electrolytic capacitors; kit of eight electrolytics (10,000 µF 16 V axial, 1,000 µF 25 V, three 10 µF, 2.2 µF 50 V, 1 µF 50 V, 47 µF 10 V); optional replacement of the 7805 with an OKI-78SR-5/1.5-W36H-C.
- ↑ 6.00 6.01 6.02 6.03 6.04 6.05 6.06 6.07 6.08 6.09 Leaded Solder, "Mattel's Little Friend", 1 August 2023 (retrieved 2026-10-19): hard-wired AC adapter with "presumably unregulated" voltages; 7805 regulators "generate a lot of heat", though the original was "probably fine"; RF shield soldered in places as well as twist-locked, and a corner pad torn while removing it; the 10,000 µF capacitor kept the power light lit about ten seconds after switch-off; RF modulator held by twisted and soldered tabs; the 7805 replaced with a Traco TSR 1-2450 in the original holes, with more switching noise as the downside; Harrington's AV adapter fitted in place of the modulator with a +5 V jumper.
- ↑ Aquarius+ (Sean Harrington), "Aquarius Computer - Motherboard Removal", YouTube, 20 September 2019 (9 minutes), description (read 2026-10-19): how to remove the motherboard "package" from the Aquarius.
- ↑ Aquarius+ (Sean Harrington), "Aquarius Computer - Removing the RF Shield", YouTube, 20 September 2019 (13 minutes), description (read 2026-10-19): removing the metal RF shield, not the RF modulator, with a desoldering vacuum.
- ↑ 9.0 9.1 9.2 9.3 9.4 Radofin Electronics (Far East) Ltd, Aquarius Guide to Home Computing, 5931-0038R-1 (1983), retyped transcription hosted here as File:Aquarius Guide to Home Computing (Radofin edition, retyped).pdf, from the Internet Archive item AquariusGuideToHomeComputing (retrieved 2026-10-19): inside cover, channels by country; "Key points for trouble free use": flat sturdy surface so the air vents on the bottom can work, not on carpet; fingers out of cartridges and ports; never lift by external wires, the Mini Expander or hand controllers; protect from excessive heat; dust cover on the cartridge port; turn off and disconnect from mains when not in use; "Find a place for your computer to live": avoid heating and air-conditioning sources.
- ↑ Evan-Amos, photograph of the underside of an Aquarius top case, 2015, hosted here as File:Mattel Aquarius top case underside.jpg (from Wikimedia Commons).
- ↑ Sean P. Harrington, "Aquarius II Computer", Get Your 8-Bit On! (retrieved 2026-10-19): an Aquarius II bought without a power supply was given one made by modifying a donated supply from an original Aquarius.