Sinclair QL - Revision history

Josh: P5 verification: correct figures and re-attribute the Repair Data citations to the T.I.S. document now hosted here; remove emoji headings

2026-09-27T08:29:00Z

P5 verification: correct figures and re-attribute the Repair Data citations to the T.I.S. document now hosted here; remove emoji headings

← Older revision		Revision as of 09:29, 27 September 2026
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	== Power supply ==		== Power supply ==

	The QL is powered by an external, custom power pack supplying '''9 V DC at 2 A''' and '''44 V peak-to-peak AC''' into connector J8. The pack uses a thyristor to limit peak voltages on the DC output but is otherwise unregulated and has significant ripple.<ref name="sm" />		The QL is powered by an external, custom power pack supplying '''9 V DC at 2 A''' and '''44 V peak-to-peak AC''' into connector '''J8''', the 3-pin socket. (Section 8.1 of the Service Manual calls this connector J3, but its own parts list assigns J3 and J4 to the BT-type control ports, so read the designator off the board.) The pack uses a thyristor to limit peak voltages on the DC output but is otherwise unregulated and has significant ripple.<ref name="sm" />

	On the board, the AC feed is rectified and regulated by '''IC37 (78L12)''' and '''IC36 (79L12)''' to give +12 V at 80 mA and −12 V at 50 mA, while the DC feed is regulated to +5 V by '''IC35''', a 7805 mounted on the large heatsink beside the Microdrives. All three regulators have thermal and short-circuit shutdown.<ref name="sm" />		On the board, the AC feed is rectified and regulated by '''IC37 (78L12)''' and '''IC36 (79L12)''' to give +12 V at 80 mA and −12 V at 50 mA, while the DC feed is regulated to +5 V by '''IC35''', a 7805 mounted on the large heatsink beside the Microdrives. All three regulators have thermal and short-circuit shutdown.<ref name="sm" />

Josh: Create Sinclair QL page set (researched from the Sinclair QL Service Manual and cited sources)

2026-08-08T19:32:41Z

Create Sinclair QL page set (researched from the Sinclair QL Service Manual and cited sources)

← Older revision		Revision as of 20:32, 8 August 2026
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	\| model = Build standards D02–D18, S13, SG18		\| model = Build standards D02–D18, S13, SG18
	}}		}}
	The '''Sinclair QL''' (for '''Quantum Leap''') is a personal computer that [[Sinclair Research]] announced on 12 January 1984 as an upper-end counterpart to the [[Sinclair ZX Spectrum\|ZX Spectrum]], aimed at serious home users, professionals and small businesses.<ref name="wp">[https://en.wikipedia.org/wiki/Sinclair_QL "Sinclair QL"], Wikipedia.</ref> It was Sinclair's last desktop machine for that market and did not achieve commercial success.<ref name="wp" />		The '''Sinclair QL''' (for '''Quantum Leap''') is a personal computer that '''Sinclair Research Ltd''' announced on 12 January 1984 as an upper-end counterpart to the [[Sinclair ZX Spectrum\|ZX Spectrum]], aimed at serious home users, professionals and small businesses.<ref name="wp">[https://en.wikipedia.org/wiki/Sinclair_QL "Sinclair QL"], Wikipedia.</ref> It was Sinclair's last desktop machine for that market and did not achieve commercial success.<ref name="wp" />

	The QL is built around a Motorola 68008 — a member of the 68000 family with 32-bit internal registers but an 8-bit external data bus — and runs QDOS, a pre-emptive multitasking operating system, with the SuperBASIC interpreter as its command line.<ref name="wp" /> The electronics were designed by David Karlin and the case by Rick Dickinson, who had styled the ZX81 and ZX Spectrum.<ref name="wp" />		The QL is built around a Motorola 68008 — a member of the 68000 family with 32-bit internal registers but an 8-bit external data bus — and runs QDOS, a pre-emptive multitasking operating system, with the SuperBASIC interpreter as its command line.<ref name="wp" /> The electronics were designed by David Karlin and the case by Rick Dickinson, who had styled the ZX81 and ZX Spectrum.<ref name="wp" />
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	''BYTE'' reviewed the machine in September 1984 and called it a "premature baby", criticising the incomplete operating system, the "dead and unresponsive" keyboard, the fragile Microdrive tapes and SuperBASIC's slow execution, while approving of the bundled Psion applications.<ref name="byte">Pountain, Dick. [https://archive.org/details/BYTE_Vol_09-10_1984-09_Computer_Graphics/page/n416/mode/1up "The Sinclair QL"], ''BYTE'', September 1984, pp. 415–419.</ref>		''BYTE'' reviewed the machine in September 1984 and called it a "premature baby", criticising the incomplete operating system, the "dead and unresponsive" keyboard, the fragile Microdrive tapes and SuperBASIC's slow execution, while approving of the bundled Psion applications.<ref name="byte">Pountain, Dick. [https://archive.org/details/BYTE_Vol_09-10_1984-09_Computer_Graphics/page/n416/mode/1up "The Sinclair QL"], ''BYTE'', September 1984, pp. 415–419.</ref>

	UK production was suspended in 1985 for lack of demand, and the QL was officially discontinued after [[Amstrad]] acquired Sinclair's computer product lines in April 1986.<ref name="wp" /> Around '''140,000''' machines were built in total across roughly 20 build standards and 16 circuit-board issues.<ref name="cowo">König, Urs. [https://www.sinclairql.net/build_standards.html "Sinclair QL Build Standards"], sinclairql.net. Source for build standards, PCB issues, chipset variants, ROM versions and production figures.</ref>		UK production was suspended in 1985 for lack of demand, and the QL was officially discontinued after Amstrad acquired Sinclair's computer product lines in April 1986.<ref name="wp" /> Around '''140,000''' machines were built in total across roughly 20 build standards and 16 circuit-board issues.<ref name="cowo">König, Urs. [https://www.sinclairql.net/build_standards.html "Sinclair QL Build Standards"], sinclairql.net. Source for build standards, PCB issues, chipset variants, ROM versions and production figures.</ref>

	Linus Torvalds owned a QL, and has said that the lack of software for it in Finland got him used to writing his own — a habit that fed into his later work on the Linux kernel.<ref name="wp" />		Linus Torvalds owned a QL, and has said that the lack of software for it in Finland got him used to writing his own — a habit that fed into his later work on the Linux kernel.<ref name="wp" />

Josh: Create Sinclair QL page set (researched from the Sinclair QL Service Manual and cited sources)

2026-08-08T19:31:31Z

Create Sinclair QL page set (researched from the Sinclair QL Service Manual and cited sources)

New page

{{Infobox computer
| name = Sinclair QL
| image = [[File:Sinclair QL.jpg|250px]]
| caption = Sinclair QL (Quantum Leap), 1984
| manufacturer = Sinclair Research Ltd
| type = Personal computer
| release date = 12 January 1984 (announced); first deliveries April 1984
| discontinued = 1986
| price = £399 (1984)
| cpu = Motorola 68008 @ 7.5 MHz
| memory = 128 KB RAM (officially expandable to 640 KB)
| storage = Two built-in Microdrive tape-loop cartridge drives
| display = 512×256 (4 colours) or 256×256 (8 colours + flash)
| sound = Single-channel, generated by the 8049 IPC
| dimensions = 47 cm × 14 cm × 5 cm
| weight = 1.4 kg
| os = QDOS with SuperBASIC in 48 KB ROM
| predecessor = [[Sinclair ZX Spectrum]]
| successor = None (line discontinued)
| codename = ZX83
| model = Build standards D02–D18, S13, SG18
}}
The '''Sinclair QL''' (for '''Quantum Leap''') is a personal computer that [[Sinclair Research]] announced on 12 January 1984 as an upper-end counterpart to the [[Sinclair ZX Spectrum|ZX Spectrum]], aimed at serious home users, professionals and small businesses.<ref name="wp">[https://en.wikipedia.org/wiki/Sinclair_QL "Sinclair QL"], Wikipedia.</ref> It was Sinclair's last desktop machine for that market and did not achieve commercial success.<ref name="wp" />

The QL is built around a Motorola 68008 — a member of the 68000 family with 32-bit internal registers but an 8-bit external data bus — and runs QDOS, a pre-emptive multitasking operating system, with the SuperBASIC interpreter as its command line.<ref name="wp" /> The electronics were designed by David Karlin and the case by Rick Dickinson, who had styled the ZX81 and ZX Spectrum.<ref name="wp" />

== Launch and reception ==

The QL was announced before it was ready to build. At the launch there was no complete working prototype, yet Sinclair took orders immediately and promised delivery within 28 days; the first customer machines only began to trickle out in April 1984, which drew criticism and the attention of the Advertising Standards Authority.<ref name="wp" />

Early production machines shipped with preliminary firmware full of bugs, and part of the operating system had to be carried on an external 16 KB ROM cartridge — known as the "kludge" or "dongle" — hanging out of the back of the machine, until the design was revised to hold the necessary 48 KB of ROM internally instead of the 32 KB originally specified.<ref name="wp" />

''BYTE'' reviewed the machine in September 1984 and called it a "premature baby", criticising the incomplete operating system, the "dead and unresponsive" keyboard, the fragile Microdrive tapes and SuperBASIC's slow execution, while approving of the bundled Psion applications.<ref name="byte">Pountain, Dick. [https://archive.org/details/BYTE_Vol_09-10_1984-09_Computer_Graphics/page/n416/mode/1up "The Sinclair QL"], ''BYTE'', September 1984, pp. 415–419.</ref>

UK production was suspended in 1985 for lack of demand, and the QL was officially discontinued after [[Amstrad]] acquired Sinclair's computer product lines in April 1986.<ref name="wp" /> Around '''140,000''' machines were built in total across roughly 20 build standards and 16 circuit-board issues.<ref name="cowo">König, Urs. [https://www.sinclairql.net/build_standards.html "Sinclair QL Build Standards"], sinclairql.net. Source for build standards, PCB issues, chipset variants, ROM versions and production figures.</ref>

Linus Torvalds owned a QL, and has said that the lack of software for it in Finland got him used to writing his own — a habit that fed into his later work on the Linux kernel.<ref name="wp" />

== Architecture ==

[[File:Sinclair QL block diagram.png|center|thumb|700px|Sinclair QL system block diagram (Figure 1.3 of the QL Service Manual): the 68008 processor with the ZX8301 master chip, ZX8302 peripheral chip and 8049 IPC.]]

The machine is built from the 68008 plus three support devices:<ref name="wp" /><ref name="sm">''[[Sinclair QL Service Manual]]'', Sinclair Research Ltd. Section 1 (System Description), Section 4 (Fault Diagnosis and Repair) and Section 5 (Parts Lists).</ref>

{| class="wikitable styled-table" style="width:95%; text-align:left;"
|+'''Sinclair QL main devices'''
! Device !! Position !! Function
|-
| Motorola 68008 || IC18 || CPU at 7.5 MHz; 32-bit internal registers, 8-bit external data bus
|-
| ZX8301 "Master Chip" || IC22 || Video display generator and DRAM refresh; made by Plessey (CLA2310, later CLA2345)
|-
| ZX8302 "Peripheral Chip" || IC23 || Microdrives, RS-232 transmit, QLAN network, real-time clock, link to the IPC; made by NCR
|-
| Intel 8049 IPC || IC24 || Keyboard and joystick scanning, RS-232 receive and sound; licensed 8049 with custom Sinclair firmware, made by Philips or NEC
|-
| HAL || IC38 || Address decode; added at Issue 6, replacing IC17 and IC27
|}

The ZX8301 divides the 15 MHz master crystal (X1) by two and distributes the resulting clock around the board and to the expansion connector.<ref name="sm" /> Because the ZX8301 steals memory cycles to fetch the display, and the 68008's data bus is only 8 bits wide, the QL performs well below what its nominal clock speed suggests.<ref name="wp" />

The 8049 was a late addition: the ZX8302 was originally intended to absorb its functions.<ref name="wp" />

== Memory and firmware ==

The QL has 128 KB of RAM as standard, officially expandable to 640 KB and in practice to 896 KB with third-party hardware.<ref name="wp" /> QDOS and SuperBASIC live in 48 KB of ROM.

At least 13 ROM releases exist. The version can be read on a running machine with <code>PRINT VER$</code>:<ref name="cowo" />

{| class="wikitable styled-table" style="width:80%; text-align:left;"
|+'''Principal QL ROM versions'''
! VER$ !! QDOS !! Notes
|-
| FB, FB.2 || 1.0x || Earliest; EPROM only, used with the external "kludge" cartridge
|-
| PM || 1.02 || EPROM, dongle
|-
| AH || 1.02 || First masked ROMs
|-
| JM || 1.03 || The common UK version
|-
| JS || 1.10 || Later UK version, fewer bugs
|-
| JSU || 1.10 || Samsung-built US machines
|-
| MGx || 1G13 || Samsung-built German machines
|}

Community-developed replacements followed, most notably '''Minerva''', a rewritten QDOS offering better speed and full support for the second frame buffer, and later Tony Tebby's '''SMSQ/E'''.<ref name="wp" />

== Video ==

The ZX8301 reads a 32 KB frame buffer in main RAM and generates five signals — red, green, blue, composite sync (CSYNCL) and vertical sync (VSYNCH) — which are routed to the 8-pin DIN monitor socket '''J7'''. The same RGB and sync signals also feed IC28, which produces composite PAL for the internal UHF modulator M1, and are mixed in transistor TR9 to give a composite monochrome output.<ref name="sm" />

Two display modes are available:<ref name="wp" /><ref name="junker">[https://junkerhq.net/xrgb/index.php?title=Sinclair_QL "Sinclair QL"], Classic Console Upscaler Wiki. Source for the video timing figures, display-mode table and the RGB connector pinout with series-resistor values.</ref>

* '''Mode 4''' — 512 × 256 pixels in four colours (black, red, green, white)
* '''Mode 8''' — 256 × 256 pixels in eight colours with per-pixel flashing

The hardware can switch between two frame buffers for double buffering, but the original firmware does not use it; Minerva does.<ref name="wp" />

The QL outputs 312 lines at 50.08 Hz with a 15.62 kHz line frequency, and '''overscans horizontally''' by roughly 24 pixels each side of the TV-safe area. This is reported to be because the ZX8301's timing constants were chosen for the flat-screen CRT originally planned for the machine, and it is why Mode 4's 85-character display needs a monitor rather than a domestic television.<ref name="wp" /><ref name="junker" /> At power-on the machine asks the user to choose with '''F1''' (monitor, Mode 4) or '''F2''' (television, Mode 8).<ref name="junker" />

== Ports and connectors ==

[[File:Sinclair QL rear ports.jpg|center|thumb|760px|Sinclair QL rear panel. UK machines use BT-style telephone connectors for the serial and joystick ports; Samsung-built export machines use DE-9 sockets instead.]]

{| class="wikitable styled-table" style="width:95%; text-align:left;"
|+'''Sinclair QL connectors (Service Manual designations)'''
! Ref !! Connector !! Purpose
|-
| J1 || 64-way Viking Eurocard || Main expansion bus
|-
| J2 || 30-way edge connector || ROM cartridge slot
|-
| J3, J4 || BT 603A LH (type 630W) || Joystick / control ports CTL1, CTL2
|-
| J5, J6 || BT 603A RH (type 631W) || Serial ports SER1, SER2 (RS-232C)
|-
| J7 || 8-pin DIN || RGB monitor output
|-
| J8 || 3-pin socket || Power input from the external supply
|-
| J9, J10 || 3.5 mm jack, single pole || QLAN network
|-
| J11, J12 || 9-way and 11-way flex || Keyboard membrane tails
|}

Connector data is from the Service Manual parts list.<ref name="sm" /> Samsung-built machines for the US and German markets replace the BT-style serial and joystick connectors with DE-9 sockets.<ref name="wp" /><ref name="cowo" />

== Power supply ==

The QL is powered by an external, custom power pack supplying '''9 V DC at 2 A''' and '''44 V peak-to-peak AC''' into connector J8. The pack uses a thyristor to limit peak voltages on the DC output but is otherwise unregulated and has significant ripple.<ref name="sm" />

On the board, the AC feed is rectified and regulated by '''IC37 (78L12)''' and '''IC36 (79L12)''' to give +12 V at 80 mA and −12 V at 50 mA, while the DC feed is regulated to +5 V by '''IC35''', a 7805 mounted on the large heatsink beside the Microdrives. All three regulators have thermal and short-circuit shutdown.<ref name="sm" />

== Microdrives ==

[[File:Sinclair QL Microdrives.jpg|thumb|360px|The two Microdrive slots, MDV1 and MDV2.]]

In place of floppy drives the QL has '''two built-in Microdrives''', using a continuous-loop tape cartridge first introduced for the ZX Spectrum in 1983, though the QL uses a different logical format.<ref name="wp" /> A formatted cartridge holds a little over 200 sectors of 512 bytes.<ref name="froschle">Fröschle, Tobias. ''Microdrives — The Inner Workings'', QL Forum; hosted in the Sinclair QL Homepage archive.</ref>

Microdrive reliability was one of the QL's most damaging problems at launch. It improved with later production — particularly the Samsung-built machines — and with aftermarket work by firms such as Adman Services and TF Services, but too late to undo the reputation.<ref name="wp" /> Microdrive cartridges were also the only distribution medium available to QL software publishers, and cost over six times as much to produce as a compact cassette, which discouraged support for the platform.<ref name="wp" />

Detailed servicing information is on the separate [[Sinclair QL Microdrive Troubleshooting Guide]].

== Build standards and board issues ==

Machines carry a build standard and serial number on a label on the underside, in the form '''Dxx-yyyyyy''' (Datatech) or '''S*xx-yyyyyy''' (Samsung).<ref name="cowo" />

* '''D''' — (THORN EMI) Datatech, the UK manufacturer. Build standards D02 to D18; at least 121,821 machines.
* '''S13''' — Samsung, North American market; 4,861 machines.
* '''SG18''' — Samsung, German market; 9,800 machines.

UK boards ran through issues ZX-83 ISS.2, ISS.4, ISS.5, ISS.6 and ISS.7; Samsung boards are numbered US3 through US6.<ref name="cowo" /> The most significant change is at '''Issue 6''' (autumn 1984, build standard D14), which introduced the HAL at IC38, removed IC17 and IC27, added resistors R102–R104 and replaced the trimmer TC1 with a fixed 22 pF capacitor C53.<ref name="sm" /><ref name="cowo" />

Samsung machines have the case interior silver-coated and other changes for FCC and VDE compliance, including '''diodes fitted piggyback on the ZX8301's RGB video output pins''' — a factory acknowledgement of the video-output fragility discussed in the troubleshooting guide.<ref name="cowo" />

== Circuit diagrams and PCB ==

{| class="wikitable styled-table" style="width:80%; text-align:center;"
! Main board !! Circuit diagram (Issue 5)
|-
| [[File:Sinclair QL motherboard.jpg|400px]] || [[File:Sinclair QL circuit diagram (Issue 5).png|400px]]
|-
! Circuit diagram (Issue 6) !! PCB component layout (Issue 5)
|-
| [[File:Sinclair QL circuit diagram (Issue 6).png|400px]] || [[File:Sinclair QL PCB component layout (Issue 5).png|400px]]
|-
! PCB component layout (Issue 6) !! Power supply pinout
|-
| [[File:Sinclair QL PCB component layout (Issue 6).png|400px]] || [[File:Sinclair QL power supply pinout.png|400px]]
|}

== Software ==

QDOS was primarily designed by Tony Tebby, with SuperBASIC written by Jan Jones.<ref name="wp" /> The machine was bundled with a Psion office suite — Quill (word processor), Abacus (spreadsheet), Archive (database) and Easel (business graphics).<ref name="byte" /> Only around 70 games were ever released for the QL, against more than 4,700 for the ZX Spectrum, which was one reason Spectrum owners saw little reason to upgrade.<ref name="wp" />

== Related machines ==

The QL's CPU, ZX8301 and ZX8302 chips and Microdrives form the basis of the '''ICL One Per Desk''', also sold as the British Telecom Merlin Tonto and the Telecom Australia Computerphone.<ref name="wp" /> After Amstrad dropped the QL, CST produced the Thor range of compatibles, and Miracle Systems sold the Gold Card and Super Gold Card processor and memory upgrades.<ref name="wp" />

== General maintenance ==
{{Main|Sinclair QL Maintenance Guide}}

The QL runs hot, its keyboard membrane is a known wear item, and the board itself needs careful handling. See the [[Sinclair QL Maintenance Guide]].

== Troubleshooting ==
{{Main|Sinclair QL Troubleshooting Guide}}

The Service Manual documents a full power-on diagnostic sequence in which the screen colour and pattern identify the failing subsystem, along with test-point voltages and a symptom table. The RGB monitor output is a particular weak point. See the [[Sinclair QL Troubleshooting Guide]].

== Capacitor replacement ==
{{Main|Sinclair QL Capacitor Replacement Guide}}

Sinclair published a complete component-level parts list for the QL, so every capacitor's designator, value and type is known. See the [[Sinclair QL Capacitor Replacement Guide]].

== See also ==

* [[Sinclair QL Microdrive Troubleshooting Guide]]
* [[Sinclair ZX Spectrum]] — the 8-bit machine the QL was intended to sit above
* [[Sinclair ZX81]]

== References ==

<references />

[[Category:Sinclair Computers]]
[[Category:1984 Computers]]