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Sony HB-F1 General Maintenance

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Sony HB-F1 main board
HB-F1 main board in the lower case, keyboard removed. The four large capacitors and the heat sink are at the rear left.

No service manual or maintenance schedule for the Sony HB-F1 has been found. The points below come from the machine's rating label, the MSX Resource Center's notes on it and its adapter, and repair reports on that site's forum.[1][2]

Power adapter

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The HB-F1 has no power supply of its own. It runs from the AC-HB3 adapter, which takes AC 100 V, 50/60 Hz and supplies DC 9 V at 1.2 A and AC 18 V at 170 mA through one plug.[3][4] Panasonic's FS-AA51 has the same plug, outputs and pin-out and can be used instead. Sony's AC-HB1 and AC-HB2P adapters cannot: their plug and voltages are different.[3]

Before connecting an adapter of unknown history, measure both outputs with no load: the DC pins against the 9 V rating and the AC pins against the 18 V rating, using the circuit diagram on the MSX Resource Center's AC-HB3 page to identify the pins.[3] Where the mains is 220 to 240 V, run the adapter through a step-down transformer.

Clock cells

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The clock built into the S1985 is backed by AA cells. The machine starts without them. Flat cells can leave bad values in the clock chip, though, and those can stop it starting, so replace weak cells or take them out.[2] Drained cells, alkaline ones especially, leak and corrode the holder and anything below it; take them out before storing the machine.[5] For cleaning up a leak see Battery Explosion, Capacitor or Corrosion Damage.

Inside the case

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No disassembly procedure for the HB-F1 has been published. With the adapter unplugged and the keyboard lifted out, the main board lies in the lower case as in the photograph above.[6] Points to note on the board:

  • Four large electrolytic capacitors stand at the rear left beside the heat sink, with smaller ones round them. Check them for leakage or bulging; see the Sony HB-F1 Capacitor Replacement Guide.[6]
  • The speed controller slider plugs into the main board. If it is left unplugged the machine starts very slowly; a jumper across its connector gives normal speed for testing.[2]
  • Leave the trimmer marked TIMER beside the S1985 alone unless you have a frequency counter and a reason to adjust it.[6]

Built-in software

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The machine starts into the Personal Databank program. Hold DEL during start-up to go straight to BASIC.[1] The MSX Resource Center describes a permanent bypass, made by cutting a bridge on the board near the MB64H444; it also loses the start-up Easter egg, and a switch wired across the cut makes it reversible.[1]

Connectors

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Cracked solder joints on the DIN, RCA and joystick connectors cause flickering video and crackling sound when a lead is moved. Reflow them.[5]

Checklist

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  1. Check the adapter's two outputs before use.
  2. Replace or remove the AA clock cells, and look for leakage.
  3. Inspect the large capacitors at the rear left and the small electrolytics in the audio and video area.
  4. Test both cartridge slots, both joystick ports and every key.
  5. Move each video and audio lead while watching the picture.

For faults see the Sony HB-F1 Troubleshooting Guide.

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References

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  1. ↑ 1.0 1.1 1.2 Sony HB-F1, MSX Resource Center wiki—link(accessed 2026-10-21) Community specification page: MSX2, 1986, Japan, ¥32,800; black, or black and red; 64 KB RAM in slot 3-3, 128 KB VRAM, Yamaha V9938, PSG, Yamaha S1985 MSX-Engine; pause button and speed controller slider, no reset button; supplied with the AC-HB3 external power adapter; replaced at the end of 1987 by the HB-F1II; built-in Personal Databank software, bypassed by holding DEL during start-up; two cartridge slots, one on top and one at the back; RF, composite video and audio, RGB (8-pin DIN), cassette, printer and two general-purpose ports. Fixes and repair: the built-in software can be disabled permanently by cutting a bridge near the MB64H444.
  2. ↑ 2.0 2.1 2.2 Trying to repair a Sony HB-F1 (MSX 2), December 2017—link(accessed 2026-10-21) Apocalypse, a console and arcade board repairer, on an HB-F1 with a black screen and the power lamp lit: the main ROM IC14, a Fujitsu MB831124 128K × 8 mask ROM in a 28-pin package, was dead; rails were correct from two +5 V regulators and a 12 V regulator; clock present, reset not stuck, activity on the buses; the EX-1 daughterboard carries only one ceramic capacitor; a Philips diagnostic ROM reported error 711 (RTC); the clock chip is inside the S1985; he fitted sockets and new Z80 and 41464 RAM chips without curing it, and the thread ends unresolved. Replies: the machine has a single mask ROM; gdx suggests a 64 KB EPROM such as a W27C512 holding only the main ROM and sub-ROM; sd_snatcher suggests a RAM cartridge in a slot to boot past faulty internal RAM, and an MSX1 BIOS to test the CPU, RAM and slot selection; with the speed controller slider disconnected the machine boots very slowly, and a jumper across its connector restores normal speed; meits: the machine makes no sound at start-up unless a game cartridge is fitted, and starts without the keyboard but then sits in the built-in software; Jipe first suggested the HIC-1, then corrected himself that the HB-F1 uses a different board; gdx: the AA batteries are not needed to start, but bad values in the clock chip can stop it starting, so replace weak batteries or take them out; gdx: check /ALM on pin 87 of the S1985 and the clock crystal pins.
  3. ↑ 3.0 3.1 3.2 Sony AC-HB3, MSX Resource Center wiki—link(accessed 2026-10-21) The external power supply supplied with the Japanese HB-F1 and HB-F1II: input AC 100 V, 50/60 Hz, 23 VA; outputs DC 9 V 1.2 A and AC 18 V 170 mA; connector sometimes called Mini-IEC; same specification, connector and pin-out as the Panasonic FS-AA51, so the two are interchangeable; the Sony AC-HB1 series and AC-HB2P use a different connector and voltages and cannot be substituted. The page shows a circuit diagram of the adapter.
  4. ↑ Rating label of the HB-F1, photographed for the MSX Resource Center wiki (File:Sony HB-F1 rating label.jpg, uploaded by Mars2000you, 3 January 2023): "MODEL HB-F1 HOME COMPUTER", input "DC9V 1.2A AC18V～170mA", ソニー株式会社, Made in Japan.
  5. ↑ 5.0 5.1 Vulnerable MSX hardware, MSX Resource Center wiki—link(accessed 2026-10-21) All MSX2 and later machines have a battery for the real-time clock; drained batteries, alkaline ones especially, leak; take removable batteries out before storage; lithium AA cells as an alternative. Lists the Sony HB-75P ("not as serious, as the problem caps are on separate small PCBs"), HB-F1II, HB-F1XD, HB-F1XDJ ("the ELNA caps are risky, the Nichicon ones are ok"), HB-F1XDmk2 and HB-F1XV among models with leaky capacitors. Fractured solder joints on DIN, RCA and DE-9 connectors cause flickering video and crackling sound; reflow them.
  6. ↑ 6.0 6.1 6.2 File:Sony HB-F1 main board.jpg, photograph of an HB-F1 main board uploaded to the MSX Resource Center wiki by Mars2000you on 13 June 2023. Read from it: "MSX2SYSTEM" printed on the board; four large electrolytic capacitors at the rear left beside an aluminium heat sink, with smaller electrolytics round them; an Omron relay at the rear; a small daughterboard marked EX-1 at the centre; Sharp LH0080A (Z80A) CPU; Yamaha S1985 MSX-Engine with a crystal and a blue trimmer marked TIMER beside it; Fujitsu MB81464-12 DRAMs; the cartridge slot connectors at the right.


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