Toshiba HX-10 General Maintenance
Routine care and safe opening of the Toshiba HX-10. No Toshiba service manual for the HX-10 has been found, so this guidance draws on the owner's manual, a published teardown of a British HX-10 and repairs reported by owners. Fault-finding is in the Toshiba HX-10 Troubleshooting Guide and capacitor work in the Toshiba HX-10 Capacitor Replacement Guide.
Mains safety
[edit | edit source]The HX-10 has its mains transformer inside the case, and the mains cord is wired straight into the machine.[1][2] Unplug it from the wall before removing any screw, and keep it unplugged while the case is open. The British model needs 240 V, 50 Hz, and Toshiba recommends a 13 A plug fitted with a 3 A fuse.[1]
Run each version only at the mains voltage it was built for. Japanese models are 100 V machines and need a step-down transformer of more than 30 W elsewhere; running them at 110 V or more can overheat the transformer and damage the power circuit.[3]
Opening the case
[edit | edit source]- Unplug the mains cord and remove all cables and cartridges.
- Turn the computer over and remove the screws in the bottom of the case, except the ones that hold the transformer.
- Turn it back over and lift the top cover with the keyboard. The keyboard is joined to the main board by two cables, on a 9-pin and an 11-pin connector at the bottom right of the board; unplug them to take the cover off completely.
[2] Three pins of the 11-pin connector feed the two keyboard LEDs, so make sure it goes back the right way round.[2]
Cartridges and the expansion bus
[edit | edit source]Always switch the computer off before inserting or removing a cartridge.[1] A lever beside the slot works the SW1/SW2 switch as a cartridge goes in.[2] Connect only Toshiba equipment to the rear expansion bus.[1] Slot expanders without their own power supply and very power-hungry cartridges add to the load on the internal supply.[3]
Heat
[edit | edit source]The HX-10 runs hot. Most of the heat comes from TR8, the B435 +5 V regulator transistor on the aluminium heat sink next to the transformer, which works as a linear regulator from about 9 V down to 5 V.[3] Measures owners have used:[3]
- Small heat sinks on the two bare regulator transistors, the D880 (+12 V) and the A473 (−12 V).
- Replacement of the large electrolytics next to the regulator with 105 °C parts.
- A CMOS Z80 (10 MHz grade or slower) in place of the NMOS Z80A, which sits in a socket. One owner measured a drop of a little over 3 °C.
- A switching 5 V module rated 1.5 A or more in place of TR8.
On one Japanese HX-10 with two cartridges fitted, the large heat sink reached 84.4 °C and the transformer about 56 °C.[3] A PAL HX-10 has a different main board; its large heat sink reached 77 °C after 20 minutes.[3]
Supply rails
[edit | edit source]| Rail | From | Regulator |
|---|---|---|
| +5 V | 8.5 V AC winding | B435 transistor (TR8) on the heat sink, with a zener reference |
| +12 V | 16 V AC winding | D880 transistor |
| −12 V | 16 V AC winding | A473 transistor |
| −5 V | Derived on the board | Feeds the 4116 video RAMs |
[2][3][4] The windings are unregulated, so their voltages vary with load.[2] One owner of a European HX-10 measured about 20 V AC on the blue transformer lead and expected about 9 V AC on the grey and brown leads.[5]
Video
[edit | edit source]The PAL encoder is a separate board with an LVA510 chip and a 4.433619 MHz crystal, joined to the main board by six wires. The RF modulator sits in a metal box with a screw that sets the channel.[2] To tune a TV, select a spare channel around channel 36.[6]
Cassette
[edit | edit source]Clean the recorder head with a head-cleaning kit when loads become unreliable, use computer or short audio tapes, and avoid the first few inches of tape.[6] The cassette motor is switched by a relay on the main board.[2]
Related pages
[edit | edit source]- Toshiba HX-10
- Toshiba HX-10 Troubleshooting Guide
- Toshiba HX-10 Capacitor Replacement Guide
- Toshiba HX-10 Owner's Manual
- Toshiba HX-22 General Maintenance
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 Toshiba, Home Computer Owner's Manual, Model HX-10, 1984, "Safety precautions", "Controls and connections" and "Program loading from ROM cartridge" (PDF pages 4, 8, 9 and 16). See Toshiba HX-10 Owner's Manual. Mains supply 240 V 50 Hz; no plug supplied; fit a 13 A plug with a 3 A fuse (blue neutral, brown live); always switch off the computer before inserting or removing a ROM cartridge, as damage to the program on the cartridge may result. Front and right side: power indicator, cartridge slot. Rear and left side: expansion bus connector (only equipment specified by Toshiba should be connected to it), composite video output, audio output, RF output, cassette recorder socket, power switch, mains cord.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Toshiba MSX HX-10 64K: Electrónica– Alejandro Sánchez, 25 May 2021—link(accessed 2026-10-21) In Spanish. Teardown of an HX-10 64K (HX-10P): remove the screws under the case except those holding the transformer, and lift the top with the keyboard, which connects to the main board through a 9-pin and an 11-pin connector (three pins of the 11-pin one feed the two keyboard LEDs); the transformer (marked 240 V, works on 220 V) gives 8.5 V AC and 16 V AC, rectified and regulated on the main board by transistor and zener regulators: a B435 on a heat sink for +5 V, a D880 for +12 V and an A473 for −12 V; Sharp Z80A with a 3.579545 MHz resonator; eight HM4864AP-15 RAMs; TMS9929A under a glued heat sink; separate PAL encoder board EMC PB3605E with an LVA510 and a 4.433619 MHz crystal, fed from the VDP by six wires; RF modulator in a metal box with a channel adjustment screw; eight 4116 video RAMs; MB83256 32 KB ROM; cartridge slot with a lever switch joining SW1 and SW2; four HD74LS367AP buffers; TCX-1007 gate array; cassette motor relay. Author's replies of 8 and 14 January 2024: the two transformer outputs are unregulated AC.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 My Toshiba HX-10 gets mighty hot!, December 2016 – March 2019—link(accessed 2026-10-21) Colemu: the heat comes from the regulator transistor TR8, a B435 on the aluminium heat sink next to the transformer (base 8.3 V, collector 5 V, emitter 9 V); the other two transistors, without heat sinks, are a D880 and an A473. gdx (whose HX-10 is the Japanese NTSC version): added small heat sinks to the two bare regulators; with a CF interface and a memory cartridge fitted the large heat sink reached 84.4 °C, the A473 about 72 °C and the D880 about 76 °C; the two capacitors nearest the hot regulator, 2200 µF 35 V and 4700 µF 16 V, were rated 85 °C, and he replaced the four largest capacitors with 105 °C parts; the CPU is socketed, and a CMOS Z80 lowered the temperature by a little over 3 °C; the transformer reached about 56 °C. sd_snatcher: Toshiba's MSX supplies run hot with heat sinks too small or missing; use Japanese models only on 100 V and European ones only at their rated voltage; avoid slot expanders without their own supply and very power-hungry cartridges; add heat sinks or a small fan; a CMOS Z80 of 10 MHz or less (not the Z84C0020) cuts the load; beware of fake Z80s. RetroTechie: TR8 works as a linear regulator from about 9 V down to 5 V, dissipating about 4 W at 1 A; a switching 78xx-type module rated 1.5 A or more in its place would cut the heat. A member, 14 April 2017: for power circuits near heat sources, choose 105 °C capacitors with a long rated life and bend their leads to keep them away from the heat. Kacper, 2019: a PAL HX-10 has a different main board; its large heat sink reached 77 °C after 20 minutes.
- ↑ Toshiba HX-10 -- unusual black screen issue!, March 2025—link(accessed 2026-10-21) WxAxNxDxExRxExR: black screen with a faulty ROM replaced; the Z80, VDP, PAL board with its LVA510, PSG and ROM all tested good in a second HX-10. sdsnatcher73: check activity on the RAM and VRAM address and data lines with a scope or logic probe, the chip selects on the RAM and ROM, then the clock and reset on the VDP and CPU. Later: about 7 V on the chips, linked to the A473 PNP power transistor TR6; with TR6 replaced the chips still saw 6.5 to 7 V; no −5 V on the 4116 video RAMs, whose −5 V supply leads back to TR6 and smaller transistors and diodes; the zener ZD3 next to TR6 was found blown.
- ↑ HX-10 Faulty transformer, December 2021—link(accessed 2026-10-21) jonwarby: a European HX-10 measured at the transformer connector with the main board unplugged gave about 20 V AC on the blue lead but only 2 to 3 V AC on the grey and brown leads, where about 9 V was expected; the supply is AC only, with the DC conversion on the main board. Manuel: also check for +5 V, +12 V and −12 V DC.
- ↑ 6.0 6.1 Toshiba, Home Computer Owner's Manual, Model HX-10, 1984, chapter 2 "Getting started" and chapter 5 "In case of difficulty", "Before calling for service" (PDF pages 13 and 39 to 43). See Toshiba HX-10 Owner's Manual. Tuning: select a spare TV channel and tune to around channel 36. If the power indicator does not light, check the wiring and the fuse in the mains plug, then consult a Toshiba dealer. Cassette problems: play back a recording to hear it; switch off VLSS or high-speed playback; clean the recorder head; use computer or normal 30 or 45 minute tapes, avoid the first few inches; use the lower transfer rate. Keyboard locked up: press CTRL and STOP together, or switch off for a few seconds. Cartridge not working: switch off and reinsert it, check its leaflet, try another. No sound, joystick or display faults: check connections, the plug fuse, the TV input selector, the COLOR setting; never use an aerial mixer; disconnect the off-air aerial when using the computer.