Sharp X1G Troubleshooting Guide
The Sharp X1G puts most of its controls on the front panel: keyboard jack, two joystick ports, volume, the SYNC MODE switch, the IPL reset and NMI reset buttons and the power button.[1] A switch in the wrong position on that panel can look like a fault, so check the panel before opening the case.
Normal start-up
[edit | edit source]At power-on the IPL program tries the floppy drive, then a ROM board in an expansion slot, then the cassette. If none answers, it shows a menu of the three boot devices and the TV timer editor.[2] The Model 10 has BASIC on tape and the Model 30 on disk.[3] An IPL menu on screen shows that the CPU, IPL ROM and video are working.
The IPL reset button restarts the machine as if it had just been switched on, without clearing memory. The NMI reset button makes the Z80 jump to a fixed address, and programs not written to handle it can freeze.[2]
Symptom table
[edit | edit source]| Symptom | Probable cause | Action |
|---|---|---|
| Nothing happens at all | Rear power switch off, no mains, or a supply fault | Check the rear switch and the AC 100 V supply. The Model 30's rating plate gives 24 W, 35 W maximum.[4] |
| No picture on an RGB monitor | Cable, monitor mode, or a main board fault | Try another RGB monitor and cable; check the IPL menu on the composite output. |
| Poor or unstable picture from the composite output | SYNC MODE switch not set to B | Set SYNC MODE to B for the composite output.[3] |
| Composite picture darker than RGB | Normal for the X1G | Adjust the television's black level.[3] |
| Graphics run slower than expected on RGB | SYNC MODE left at B | Position B shifts the CRTC timing and adds graphics RAM wait states; switch it back.[5] |
| Software freezes after reset | NMI reset pressed | Use the IPL reset button instead.[2] |
| Keyboard dead | Keyboard cord, front jack, or keyboard | See Keyboard faults. |
| Joypad or joystick dead | Wrong controller type, or a controller that needs power | The ports are Atari-type with no power pin; most MSX-style joysticks work, and auto-fire pads that need power must have their own supply.[2] |
| Disk read errors (Model 30) | Disk written in 2D mode on a three-mode drive, dirty heads, or a drive fault | Use disks written on 2D drives; clean the heads; see Floppy Drive Repair.[6] |
| Tape stops as soon as it starts (Model 10) | Tape end detected because the take-up drive or counter is not turning | Check the rubber ring and counter belt; see General Maintenance. |
Keyboard faults
[edit | edit source]The membrane keyboard sends key codes one way to the computer over a single wire, with +5 V on the plug's tip, the data on the ring and ground on the sleeve.[7][1]
- With the computer on and the keyboard unplugged, measure between tip and sleeve of the front jack. Expect +5 V.[7]
- If the keyboard works only with the plug pushed one way, reflow the jack's solder joints.[8] The X1G has only the one keyboard jack.[1]
- Check the coiled cord for a cracked sheath.[9]
- With +5 V present and the cord sound, look at the ring line with an oscilloscope while pressing a key. No pulses point to the keyboard; pulses with no response point to the computer.[7]
A keyboard that will not report two ordinary keys held at once is working normally; only Shift and similar keys combine.[2]
Floppy faults (Model 30)
[edit | edit source]The two drives are 5¼-inch 2D units made by ALPS, and the Model 30 has no socket for an external drive.[10] Once BASIC has loaded, try a problem disk in the other drive to tell a drive fault from a disk fault. A disk written in 2D mode on a three-mode drive, such as the CZ-520F or the drives of the X1turbo III and turboZ, may give read errors in a 2D-only drive like the X1G's.[6]
Data recorder faults (Model 10)
[edit | edit source]X1 Center's notes on other X1 decks give two failures that stop tape loading:[11]
- The head does not load: the loading belt has broken or melted.[11]
- The head loads and the deck stops at once: the take-up spool is not turning and the computer reads tape end. Turn the spool by hand; if the deck keeps running, replace the drive ring.[11]
Power supply
[edit | edit source]The X1G's power supply circuit has not been published.[12] Its rating plate gives 24 W, 35 W maximum, for a Model 30.[4] After any repair to the supply, power the machine through a plug-in wattmeter and compare the reading with that rating. X1 Center tested a repaired first-model X1 supply this way, from a current-limited source, so that a remaining fault could not destroy the new parts.[13]
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 ゲームプレイ画面を録画可能！ X1シリーズで初めてビデオ出力端子を備えた「X1G」– 佐々木 潤 (Jun Sasaki), AKIBA PC Hotline! (Impress), 2019-01-29—link(accessed 2026-10-21) Front panel from the lower left: keyboard jack, two joystick ports, volume knob, sync mode switch, IPL reset, NMI reset, and a long red power switch at the right end; rear panel: digital RGB, TV control, CMT, video output, printer, audio output, I/O slots and a power switch; the X1G was the first X1 with a video output; membrane keyboard; supplied with an X1-logo joypad like the Famicom controller.
- ↑ 2.0 2.1 2.2 2.3 2.4 X1 (コンピュータ), Japanese Wikipedia—link(accessed 2026-10-21) IPL boot order FDD, ROM board, CMT, then a menu with the TV timer editor; the IPL reset (from the X1turbo and X1F on) restarts as at power-on and does not clear memory; NMI reset jumps to 0066h and can freeze software not written for it; joystick ports are 9-pin, Atari-compatible, with no power pin, and most MSX-style joysticks work; the keyboard cannot report simultaneous key presses other than Shift and similar keys. X1G: membrane keyboard; supplied joypad CZ-8NJ1; Model 30 has no external FDD interface.
- ↑ 3.0 3.1 3.2 Oh!MZ, July 1986, pp. 58-61, "新登場X1Gを見る" and the CZ-820C/822C specification table: Model 10 supplied with cassette BASIC CZ-8CB01 V2.0 and V1.0; Model 30 with disk BASIC CZ-8FB01 V2.0 and V1.0 and cassette BASIC CZ-8CB01 V1.0; to use the multi-visual (composite) output set the front SYNC.MODE switch to B; the composite picture is a little darker than RGB and adjusting black level gives a clear enough picture; RGB separate and composite outputs; two Atari-type joystick ports; AC 100 V. Scan on the Internet Archive, item OhMZ_1986-07.
- ↑ 4.0 4.1 Rear panel photograph, File:Sharp X1G Model 30 rear panel.jpg (AKIBA PC Hotline!): rating plate of a CZ-822CE, AC 100 V, 50/60 Hz, 24 W (35 W maximum); POWER switch at the top right of the rear panel; RGB OUT, TV CONTROL, CMT and M.V. OUT sockets.
- ↑ X1/turbo/Zシリーズ拡張コネクター等一覧, X1 Center—link(accessed 2026-10-21) Composite output (X1G, X1twin): NTSC composite for monitors without RGB input; switching SYNC to B approximates NTSC timing and improves the picture, but the CRTC timing shifts and graphics RAM waits increase. Joystick interface: signal names for port 2 are IOB0 to IOB7; the first X1 had no pull-ups, later models added them.
- ↑ 6.0 6.1 祝一平 (Iwai Ippei), 試験に出るX1 ハードウェアのフルコース (Nihon SoftBank, 1987), p. 217: a 2D disk written on a 2D/2DD/2HD drive is not guaranteed to read on 2D-only drives, which include the X1G's internal drives; on the author's test a turbo drive failed from track 35. Scan on the Internet Archive, item SHARPX1TecRef.
- ↑ 7.0 7.1 7.2 佐藤 達之 (Sato Tatsuyuki), SHARP X1/X1Turbo キーボード端子 通信仕様 Ver 0.1, 2001, X1 Center, x1kbd.pdf, p. 1: one-wire serial from keyboard to main unit only, like an infrared remote control code, with a low header and data bits set by the spacing of low pulses; 3.5 mm stereo mini jack, +5 V tip, transmit signal ring, ground sleeve.
- ↑ キーボードコネクタの半田剥離, X1 Center—link(accessed 2026-10-21) Keyboard connector solder cracks are one of the most frequent faults on X1, turbo and Z machines; the symptom is a keyboard that works only with the plug under tension in one direction.
- ↑ X1/turbo用キーボードケーブルの劣化と交換, X1 Center—link(accessed 2026-10-21) The sheath of X1 and X1turbo keyboard cords crumbles with age; the cord carries +5.0 V.
- ↑ X1/turbo/Zシリーズ搭載FDDインターフェース仕様, X1 Center—link(accessed 2026-10-21) CZ-822C: two 5¼-inch 2D drives, ALPS make, model not identified; 1 kΩ terminator; no external FDD connector; internal drive cable not replaceable.
- ↑ 11.0 11.1 11.2 CZ-800Cカセットデッキの修理メモ, X1 Center—link(accessed 2026-10-21) First X1 deck: if the head does not load, the loading belt has broken or melted; if the head loads and the deck stops at once, the computer has detected tape end because a cracked play-feed ring leaves the take-up spool still; turning the spool by hand and seeing the deck keep running shows that the ring is at fault and the sensor is working.
- ↑ 図面資料, X1 Center—link(accessed 2026-10-21) Schematics hosted: CZ-800C (X1), CZ-850C/851C/852C (X1turbo), CZ-8RL1. No X1G schematic.
- ↑ CZ800C電源修理・・・できなかった。, X1 Center—link(accessed 2026-10-21) Test of a repaired first X1 (CZ-800C) supply from a 12 V 5 A supply through a 60 W inverter and a socket wattmeter, so that a short could not do further damage; a failing supply can lose efficiency and draw more power.
