MX-5050BII: the one people mean when they say MkII
What it is↑ TOP
The MX-5050BII is the generation after the MX-5050B, on sale from about 1981. It is the last of the line to wear the plain MX-5050 badge before the BIII arrived around 1990, and it is by a wide margin the most common MX-5050 in circulation today.
It is on this site for one reason. The Mini Pro is a first-generation machine, and this page's subject is not — but the BII is the machine people mean when they write "MkII", and that confusion runs through every forum thread and every eBay listing about early Otari decks. The wider family argues the distinction at length. This page exists so the argument has the BII's own paper behind it.
Its factory book describes a three-speed DC-servo direct-drive capstan, two six-pole induction reel motors, active balanced input and output circuits, a built-in two-frequency test and cue oscillator, motion sensing, an edit control, a memory stop, and a computerised elapsed-time indicator with an LED display. The amplifier panel carries a reference flux level indicator and a standard reference level output switch — the front-panel descendants of the SRL trimmers the Mini Pro hides behind two holes in its faceplate.
How to identify one↑ TOP
- The rear plate. As with every MX-5050, the face says only "MX-5050"; the designation is on the plate. See the face badge.
- Three speeds, switched. The BII ships set to 15 and 7½ ips and converts to 7½ and 3¾ by a documented user procedure, so a BII may legitimately be running either pair. The Mini Pro's speeds are fixed by its pulley.
- A digital tape timer. An LED elapsed-time display with a memory stop. No first-generation machine has one.
- A NAB/IEC switch and per-speed equalisation pots. Front-panel record bias, equalisation and level controls, adjustable per speed.
- It is not a Mark II. The Mark II is a 1977 desk-top machine in two boxes, with the transport and electronics separated. A BII is one chassis.
Specifications↑ TOP
Only what this site's own copy of the factory book states. Table 1-1 of the instruction manual, in its own terms:
| Model | Head format | Speed | Tape |
|---|---|---|---|
| BII-2 | 2-track, 2-channel | 15 and 7½ ips | ¼″ |
| BII-4 | 4-track, 2-channel | 15 and 7½ ips | ¼″ |
| BII-F | Full track, mono | 15 and 7½ ips | ¼″ |
| BII-2E | 2-track, 2-channel DIN | 15 and 7½ ips | ¼″ |
Read the second row carefully. The BII-4 is a quarter-track, two-channel machine, not a four-channel one. Otari's suffix digit counts tracks, not channels, exactly as it does for the 4SH — the Specs page makes the same point about the first generation.
All four convert to 7½ and 3¾ ips by the procedure in the manual's Section V.
Documents
Service training binder
Instruction manual (OS3-038, Edition 6, September 1984)
Wanted
BII service documentation
The instruction manual on this page is Otari's combined book: operation, alignment, transport maintenance, parts lists and circuit diagrams in one binding. What is not here is anything Otari issued beyond it — a service bulletin, a revision notice, an addendum sheet, or a later edition than the sixth. If you hold BII paper that is not this book, it is wanted.
Have one? Here is how to contribute.
Sources↑ TOP
- Instruction manual, OS3-038 — Edition 6, September 1984. Table 1-1 for the model list, Section 1.1 for the system description, Section V for the speed conversion.
- The wider family — why a MkII is not a BII, and where the BII sits in the line.
- Service training binder — head assembly KH-41IA serving "BII2, MKIII-2", the cross-reference that ties this machine to the MARK line.
Have one, or paper for it?↑ TOP
The book is here; the machine is not. A BII owner with a rear plate, a head-block photo, or the separate service documentation would turn this from a page about a manual into a page about a recorder. See how to contribute.