Toshiba HX-22 General Maintenance
Routine care of the Toshiba HX-22. No Toshiba service manual for the HX-22 has been found, so this guidance draws on the MSX Resource Center wiki, photographs of the board and repairs reported by owners. Fault-finding is in the Toshiba HX-22 Troubleshooting Guide and capacitor work in the Toshiba HX-22 Capacitor Replacement Guide. The Toshiba HX-10 General Maintenance guide covers the HX-10, whose power supply has the same weaknesses.
Mains safety
[edit | edit source]The HX-22 has its transformer inside the case, with a separate power supply board, and takes mains through an AC inlet.[1][2] Unplug it before opening the case. The European versions also have a ground terminal.[2]
Run each version only at its rated mains voltage. The Japanese HX-22 is a 100 V machine; 110 V or 127 V can melt the transformer or burn the power supply board.[3]
Cartridges
[edit | edit source]The HX-22 has two cartridge slots, one on top and one at the back.[2] A label above the slots on the Japanese model says to change cartridges only with the power switch off and the power lamp out.[4] Slot expanders without their own power supply and very power-hungry cartridges overload the internal supply.[3]
Heat
[edit | edit source]Toshiba's MSX power supplies run hot because their heat sinks are too small or missing, and the load from modern cartridges makes it worse.[3] Measures recommended for Toshiba MSX1 machines:[3]
- Add heat sinks to the regulators that have none.
- Fit a small 12 V fan (4 × 4 cm) over the largest heat sink, which belongs to the +5 V regulator. In a Japanese HX-22 one owner fixed the fan with a single screw, turned through 45 degrees; the HX-2x models have room inside for it.
- Replace the NMOS Z80A with a CMOS Z80 rated at 10 MHz or less, from a reliable supplier.
Replacement capacitors near the heat sinks should be 105 °C parts.[3]
Power supply board
[edit | edit source]The power supply board is the same shape across the HX-20, HX-21 and HX-22. Its regulators are built from transistors, zener diodes and an op-amp, with no protection circuits.[1] An owner who recapped the whole machine and replaced the transistors, zeners and op-amp on this board still found an audible wavy noise on the 5 V and 12 V rails, and designed a protected drop-in replacement board that reuses the original heat sinks and wiring.[1] Another approach for Toshiba MSX1 machines is to replace the transformer and power board with a switching supply.[3]
Video
[edit | edit source]The video board at the top left of the case is separate from the main board and carries the RGB output.[4][5] The main board's video RAM is eight 4116-type chips, which need a −5 V supply as well as +5 V and +12 V.[4][6]
Firmware and RS-232C
[edit | edit source]The European versions show a word processor menu at start-up; hold ESC while booting to skip it.[7] On the Japanese model the word processor (started with _JWP or _JWPKAKU) needs a kanji ROM cartridge in one of the slots.[5] The RS-232C interface has its own on/off switch.[2]
Related pages
[edit | edit source]- Toshiba HX-22
- Toshiba HX-22 Troubleshooting Guide
- Toshiba HX-22 Capacitor Replacement Guide
- Toshiba HX-10 General Maintenance
References
[edit | edit source]- ↑ 1.0 1.1 1.2 MSX Toshiba Pasopia IQ HX-20 HX-21 HX-22 Improved PSU, March 2022—link(accessed 2026-10-21) kinchan, 16 March 2022: a replacement power supply board with the same form factor as the original for the Pasopia IQ HX-2x series, reusing the original heat sinks and wiring, with low-noise LDO regulators, very low output ripple, and protection against over-voltage, overload, short circuit, reverse current and over-temperature. kinchan: after recapping the whole machine and replacing the transistors, zener diodes and op-amp on the original power board, the 5 V and 12 V rails still carried an audible wavy noise that reached the stereo audio; the original board has no protection, which exposes the transformer and the main board to failure.
- ↑ 2.0 2.1 2.2 2.3 Toshiba HX-22, MSX Resource Center wiki—link(accessed 2026-10-21) Community page for the HX-22 series: an improved HX-21 with a built-in RS-232C interface with an on/off switch; models HX-22 (Japan, QWERTY/JIS, RF, composite, stereo audio, RGB on an RP13A connector), HX-22CH (Switzerland), HX-22GB (UK) and HX-22I (Italy), the European ones with mono audio and RGB on SCART; released 16 October 1984 in Japan and 1985 in Europe; prices JP ¥89,800, UK £149.99, IT L. 599,000; 64 kB RAM in slot 3-0 on the HX-22, split between slots 0 and 3-0 on the HX-22I; 16 kB VRAM; TMS9928A or TMS9929A; AY-3-8910A; Toshiba TCX-1010 gate array in the HX-22, TCX-1012 in the HX-22I; a 32 kB firmware ROM (word processor); Sharp LH-0080A Z80A; two cartridge slots, one on top and one at the back; joystick ports and data recorder connector on the right side; connections: RF (with channel selector on the Japanese model), audio and composite video, RGB, RS-232C (DB-25) with on/off switch, data recorder, Centronics printer port, two joystick ports, two cartridge slots, AC power plug, ground terminal on European versions only. On the HX-22I the RAM split can make badly written software crash.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 My Toshiba HX-10 gets mighty hot!, December 2016—link(accessed 2026-10-21) sd_snatcher, 9 December 2016: Toshiba's MSX power supplies are among the worst on MSX machines, with heat sinks too small or missing, and run hot, worse with expansions and modern FPGA or CPLD cartridges; run Japanese models only at 100 V (never 110 V or 127 V, which can melt the transformer or burn the power supply board) and European models only at their rated voltage; avoid slot expanders without their own supply and very power-hungry cartridges; add heat sinks to the regulators that lack them and a 4 × 4 cm 12 V fan over the largest heat sink, the +5 V regulator (on the Japanese HX-22 he fixed the fan with one screw, turned 45 degrees); replace the NMOS Z80A with a CMOS Z80 of 10 MHz or less; MSX1 models can take a switching supply in place of the transformer and power board. In the HX-2x models there is room inside for a fan. gdx, December 2016 (on a Japanese HX-10): the two capacitors nearest the hot +5 V regulator were 2200 µF 35 V and 4700 µF 16 V parts rated at 85 °C; capacitors next to the hot regulators need a 105 °C rating where the temperature passes 80 °C.
- ↑ 4.0 4.1 4.2 File:Toshiba HX-22 main board.jpg, photograph of a Japanese HX-22 main board, uploaded to the MSX Resource Center wiki by Mars2000you on 13 December 2015. Read from it: the video board with its electrolytics at the top left, the cartridge slots at the top right, a Z80A (IC1), two Toshiba TMM23256P ROMs (IC2, IC3), the Toshiba TCX-1010 gate array, a GI AY-3-8910A, eight TMM416P-2 video RAMs (4116 type, IC37 to IC44), eight HM4864AP main RAMs, and a few small electrolytics on the main board near the joystick and cassette connectors. A label over the cartridge slots says, in Japanese, that cartridges must be changed only with the power switch off and the lamp out.
- ↑ 5.0 5.1 Toshiba HX-22, MSX Resource Center wiki—link(accessed 2026-10-21) The Japanese HX-22 (Pasopia IQ) has stereo PSG sound with a switch at the back and can use part of its memory as a RAM disk; launch price ¥89,800; built-in Japanese word processor firmware (Kanji-Kun v2.0), started with _JWP or _JWPKAKU, which needs a kanji ROM cartridge such as the HX-M200 or HX-M201; the firmware adds RS-232C, printer and Memory Disk BASIC commands; localised as the HX-22GB, HX-22I and HX-22CH; the gallery includes the RGB pinout of the video decoder board of the HX-21 and HX-22.
- ↑ Toshiba HX-10 -- unusual black screen issue!, March 2025—link(accessed 2026-10-21) On a Toshiba HX-10 with a black screen, the 4116 video RAMs had lost their −5 V supply and the logic saw 6.5 to 7 V after a zener in the supply section failed. sdsnatcher73: with correct supplies, check activity on the RAM and video RAM address and data lines with a logic probe or oscilloscope, the RAM and ROM chip selects, and the clock and reset of the VDP and CPU.
- ↑ Toshiba HX-22GB, MSX Resource Center wiki—link(accessed 2026-10-21) The British adaptation of the HX-22: an English word processor in place of the Japanese one, mono PSG sound, no Memory Disk and no extra printer BASIC commands; a firmware menu appears at start-up and can be skipped by holding ESC while booting; the firmware adds the RS-232C BASIC commands. The HX-22I page gives the same description for the version sold in Italy and Spain.