2026-10-08
The BQ-II manual arrived
The last of the books from the eBay run has arrived. It is OS3-031, the BQ-II's instruction and maintenance manual. Until now the library held this book worst of all. Its only copy was an OCR transcription laid out in Word, with the figures pasted in as pictures and the OCR's mistakes printed on the page. The paper is now here, and it has been scanned.
The cover matches what the listing photograph promised. It prints Parts No.OS3-031, which settles the catalog number the transcription had only hinted at as "053-031". Below that are Edition No.2 and Issued: November 1983, and across the middle someone has written ¼" 4 TRACK in red pen.
The scans
The book went through the scanner at 1200 dpi, 143 pages in all. The 1200 dpi PDF is the full-resolution archive copy, at 433 MB. The 600 dpi PDF is a cleaned copy at 129 MB, and it is the one the BQ-II's documents card now offers first. Both are page images with no text layer. The OCR transcription stays on the card as a third download, for the record.
What the paper shows that the transcription could not
It is not the same text. The book has 143 pages, each numbered within its section, so page 7-16 is the sixteenth page of Section 7. The Word copy has 130, and the difference is not only layout. It is a different revision of the book. Its specification table gives the signal-to-noise as 69 dB weighted and 66 dB unweighted; the paper prints 53 dB (NAB) and 54 dB (IEC). Its crosstalk is 55 dB, the paper's 50; its erase efficiency 70 dB, the paper's 72. Its frequency response is ±2 dB where the paper prints +2, −3 dB, and its SEL/REP limits differ too. The page that tells owners how to reach Otari is reworded, and the paper's version lists offices in Singapore and the United Kingdom that the Word copy lacks. The paper's contents also list six entries the Word copy's contents leave out, and the paper adds two pages listing every figure and table.
The type. The text is set in a typewriter face whose lowercase l is drawn like a capital I, so the printed page reads "equal Izer" and "Is". That ambiguous letter is the likely source of many of the transcription's misread letters, "AI I" among them.
The schematics. The transcription ended at the pin identification pages, and the digital edition used to say Section 10 prints no schematics. The paper goes two pages further. Next comes a typed index headed MX5050 BQ2 TAPE RECORDER, SCHEMATIC DIAGRAMS, TYPE I, and dated 12.SEP.1984, ten months after the cover's issue date. It lists nine drawings:
| Otari part no. | Assembly | Dwg. no. |
|---|---|---|
| PB76E0A | HEAD Connection PCB Ass'y | 4-28961 |
| CB3170A | Tape Transport Wiring Diagram | 3-7695 |
| PB82L0A | Timer PCB Ass'y | 4-28963 |
| PB44S0BA | Control PCB Ass'y | 3-8376 |
| PB82R0A | MIC ATT PCB Ass'y | 4-28965 |
| PB14Z0A | REC REP AMP PCB Ass'y | 3-8497 |
| PB45E0A | AMP Control PCB Ass'y | 3-6649 |
| PB76D0A | Mother PCB Ass'y | 3-6287 |
| PB15A0A | HEAD PHONE PCB Ass'y | 3-6399 |
After the index comes the first of those drawings: the head PCB connection diagram, 4-28961. It wires twelve head channels to a 28-way connector. Each erase channel (E1 to E4) passes through a 1 Ω resistor and each record channel (R1 to R4) through a 10 Ω resistor. The four playback channels (P1 to P4) are wired direct. The other eight drawings are not in this copy. The index at least gives every one of them a name and a number to look for.
A note in the margin. Under 7-6-(3), the frequency response procedure on page 7-16, someone has written: Adjust VR 104 For Low Freq Compensation adjust 50 Hz to match 500Hz level. The printed procedure trims only the 10 kHz controls, VR 102 at 15 ips and VR 103 at 7½. The note is a working owner's addition for the low end, and it stays that: it is not part of the printed procedure.
The edition, rebuilt
The digital edition has been rebuilt from the paper. Every page was transcribed again, word for word, from the 600 dpi scan. The edition's test now checks each section against that transcription instead of the Word copy's text layer. Every section was then corrected until the two agree.
Most of what the old edition marked as the book's errors were the OCR's. It carried 95 marks. Of those, 70 are gone. In 67 the paper prints the right text: "053-031" is OS3-031, "Ashley" is Ass'y, the parts lists' "KCOB011A" is KC0B011A. The other three only noted part numbers where the MARK III/4 manual differs, which is not an error. 25 are real misprints in the paper and stay marked, now with crops of the paper. Ten more mark misprints the old edition had missed or corrected without saying so, such as "follwoing", "locknot", "Cantrol" and a "Knop Washer". Specifications, captions and parts lists now read as printed.
All 70 figures were rebuilt from the scan. The exploded views and pin diagrams are crops of the paper, and the 43 traced drawings were traced again from it. The schematic index and drawing 4-28961 are now at the end of Section 10, with a note on what the drawing's own title block says. The Mark III specifications page has the paper's figures. The parts cross-reference has 29 BQ-II part numbers corrected or re-read, most of them a zero the OCR read as a letter O.