QX / QXD / QXHD: the quarter-inch four-channel
¼″ quarter-track 4-channel
Designations
- MX-5050-QX
- MX-5050-QXH
- MX-5050-QXL
- MX-5050-QXD
- MX-5050-QXHD
- MX-5050-QXLD
Compare the multichannel MX-5050 models →
Search service parts and donor leads for this model →
What it is↑ TOP
The QX is the first generation's quarter-inch four-channel machine. It is on the panel photo of Otari's September 1975 tri-fold brochure, whose S/N table quotes it beside the two-channel machines (1975 brochure), and Audio's October 1976 directory lists its drive motor as DC servo alone where the two-channel machine lists both (Audio, October 1976). By 1978 the line-up ad calls it the QXHD. Otari's maintenance manual OMM-1002E covers the QXD with the 2SD₂, ½QXD and 8SD — four configurations that shared a service book (OMM-1002E). A period copy of that manual has "MKII-2" and "MKII-4" hand-lettered over the 2SD₂ and ½QXD on its cover, which is how the book came to be taken for a Mark II manual; those two are the Mark II-2 and Mark II-4.
How to identify one↑ TOP
- Quarter-inch tape with a four-channel head block.
- The rear identification plate, not the face badge, gives the full model code. Factory documents use QXH/QXL, QXD and QXHD designations; we do not yet have a QXD plate photograph. See the face badge.
- A DC-servo capstan, or not. Audio's 1976 directory lists DC servo alone for the QX, but the 1976 Stereo Directory lists an AC QXH at $2050 beside the DC-servo QXH-S at $2250 (Stereo Directory, 1976, PDF p.109), and Otari's operation manual lists the QXH and QXL under the hysteresis-synchronous transport (OIM-1005E, Table I-1). A QX may have either capstan.
Specifications↑ TOP
For the later QXD, Otari gives tape width, track layout, speed, frequency response, signal-to-noise ratio and other figures in OIM-1004E, Table 1-6. The earlier QX appears separately in the 1975 brochure's S/N table. Use that brochure for its stated conditions; do not assume its figures apply unchanged to the QXD.
Documents
Start with the manual
Operation manual (OIM-1005E)
Covers the first-generation MX-5050
Read the digital editionDownload PDFDownload the 1200 dpi scan (46 pages, 143 MB)
Instruction and preventive maintenance manual (OIM-1004E)
Covers MX-5050 2SD₂ (MKII-2), QXD, ½QXD (MKII-4) and 8SD
Includes preventive maintenance and four fold-out schematic and wiring sheets.
Service and repair
Service training binder
Covers the whole MX-5050 line
Maintenance manual supplement (OMM-1002E)
Covers MX-5050 2SD₂ (MKII-2), QXD, ½QXD (MKII-4) and 8SD
Section 7 schematics and PCB X-ray views, redrawn
Covers the QXHD
Community submission · from Chris, a QXHD owner in Delaware
Specifications and sales
Sales brochure — Compact Professional Tape Recorder (B-103A, September 1975)
Covers the MX-5050 line, including the four-channel QX
Read the digital editionDownload PDFDownload the 600 dpi assembly (5 pages, 57 MB)
Period press
The family archive also covers other models in this line.
Browse all 20 First generation Period Press sightings →Sources↑ TOP
Factory documents
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Sales brochure, September 1975 — the QX on the panel photo and in the S/N table.
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Operation manual, OIM-1005E — Table I-1, the QXH and QXL on the hysteresis-synchronous transport.
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QXD instruction manual, OIM-1004E — model table and Table 1-6 specifications.
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QXD maintenance supplement, OMM-1002E — QXD service procedures, schematics and parts lists.
Period press and catalog
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Audio, October 1976 — the directory's drive-motor column.
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Stereo Directory, 1976 — PDF p.109, the QXH at $2050 and the DC-servo QXH-S at $2250.
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db, January 1978 — the QXHD in the line-up ad.
Site context
- The wider family — the shared maintenance manual title.
Have one, or paper for it?↑ TOP
For the QXD, we have the instruction manual and maintenance supplement, which also cover the 2SD₂, ½QXD and 8SD. The earlier QX appears in OIM-1005E and the 1975 brochure. No QXD-specific brochure or data sheet is held, and we have no photograph of a QXD's rear plate. An owner with either would strengthen this page. See how to contribute.
A QXHD owner has sent in redrawn Section 7 sheets and his restoration notes.