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This webpage documents the refurb of an Otari MTR-10 half track tape deck, done back in 2012. This was a popular professional studio recorder dating from the 1980s. This unit was cleaned up, completely recapped, and adjusted and aligned. Every electrolytic capacitor was replaced (the originals were 25+ years old at the time) in the power supply, the transport (for reliability purposes) and the audio circuits (for both reliability and audio qualiity).
In the transport and control circuits, the replacements were primarily Panasonic FC type (a long-life 105° cap), and on the audio cards, Nichicon Muse bi-polars were used in the audio path. In addition, the signal path caps were all bypassed with small value polypropylenes. The power supply was rebuilt as well, primarily with Panasonic TS caps. In addition, the wiring from the headblock was upgraded and connectors were added to allow use of an external tape head preamp. The unit was then aligned (using a Sound Technology 1500) for both NAB and IEC 15ips playback.
This is the MTR-10. Most of the audio and transport electronics are on plug-in PCB modules below the transport. Those boards have a variety of adjustment trimpots to align the unit.
A closer look at the transport section showing the head block and controls.
And the meter bridge.
The top plate/transport section lifts up to allow access to the capstan motor (black cylinder on the right) as well as the supply and take-up motors and associated electronics.
Two motor control PCBs between the supply and take-up motors. Both easily unclip and pull out for service.
A closer look at the bottom section of the deck. The plug-in boards are as follows: Audio (left), Audio (right), Audio Control (EQ, oscillator), Capstan Control, Reel Control, Master CPU, and Transport Control. The bottom section is the power supply for the deck with indicators for various voltages.
The rear of the unit opened up showing the motherboard that all the PCB modules shown above are plugged into. Input and output XLRs are on the lower right.
A view of the inside of the power supply sub-chassis showing the PCB along with the power transformer at the top (which is the front) and showing the heatsink at the rear for voltage regulators and rectifier bridges.
The power supply PCB after being re-capped with Panasonic TS (105°) caps.
The inside of the meter bridge, from the back. VU meters and associated circuitry to the right, playback speaker to the left with the audio playback amplifier just to the right of the speaker.
This is one of the audio PCBs after being re-capped. I used Silmic IIs (brown caps) and Nichicon Muse bi-polar caps (green) in the signal path.
This is the foil side of the audio PCB. Note the newly added red film bypass caps which are mounted beneath each electrolytic on the other side of board.
The gold pins for connecting the board are clearly visible at the bottom, used to make the power supply and audio connections for that channel.
The Audio Control PCB, after re-cap.
The Master CPU PCB, after re-cap.
The Transport Control PCB, again after re-cap.
The tape counter assembly (with the display to the right) which mounts in the top plate of the unit.
In order to facilitate use of a separate tape head preamp, I upgraded the wiring from the headblock with low capacitance Belden shielded cable with Cardas SLVR RCA connectors. Shown here feeding the stock playback electronics, but can be jumpered to feed an external tape head preamp.
Testing and alignment with the Sound Technology ST-1500 (two in fact). A prototype tape head preamp is on the bench (center bottom) to be mounted in the opening on the left in the base of the MTR-15.
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