====== Sony MZ-R90/R91 ======

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At the time of their release, they were the smallest recorders with the longest playback time available.  The R90 and R91 seem very similar except for the fact the R90 was slightly slimmer/lighter and had a magnesium top cover.

User reviews say that due to power saving drive, it can be slow to start-up/respond.

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Common problems for this model include:

  * Cracked flex PCB cables
  * Brittle plastics (especially battery compartment)
  * Shorts due to spilled battery electrolyte
  * Optical pickup failures
  * Original power supply out-of-spec

[[http://marlene-d.blogspot.com/2012/11/review-sony-mz-r-9091.html| ATRAC IC is a CXD-2660GA which uses version 4.0 or 4.5 (measurments are inconclusive)]]
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Content adapted from: [[https://www.minidisc.org/part_Sony_MZ-R90+R91.html|MZ-R90/R91 Minidisc.org Page]], [[https://www.sony.jp/CorporateCruise/Press/199908/99-0824/| Sony Press Release]]
[[https://web.archive.org/web/20001109123700/http://www.minidisc.org/brian_youn/r90831.html#wishlist| Comparison with Sharp MD-MT831]]
===== Manuals =====

{{:equipment:sony:portable:mz-r90user.pdf | MZ-R90 User Manual}}

{{:equipment:sony:portable:mz-r90service.pdf | MZ-R90 Service Manual}}

===== Photos =====

MZ-R90

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MZ-R91

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===== Servicing =====

You can enter the test mode by setting the **HOLD** switch to on, holding **PLAY** and pressing the following sequence:

**Next, Next, Previous, Previous, Next, Previous, Next, Previous, Pause, Pause**

Alternatively you can short the test mode pad shown below:

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As you enter the servicing mode you will be in display check mode. 

The servicing manual recommends the following steps:

   - Clear settings saved in device memory (Manual mode - 021 ResNV)
   - Perform electrical adjustments (Manual mode - 762 through 767)
   - Calibrate temperature measurement (Manual mode - 014 SetTmp)
   - Perform automatic adjustment (ASSY11)
   - Clear clock (Manual Mode - 043 Resume)

Sometimes to pass automatic adjustment you may need to also use manual options 031 for CD and 034 for MO.

The locations of pads for electrical adjustment are shown below.

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Example: adjust VC PWN duty (762):

  - **Vol+** - Manual mode
  - **Vol+** 7 times - 700 POWER
  - **Play** - 710 PwrChk
  - **Vol+** 5 times - 760 V_ADJ
  - **Play** - 761 PwrSel
  - **Next** - 762 VclPWM
  - **Vol+/-** to adjust voltage between TP915 and GND to 2.500V
  - **Pause** to save
  - **Stop** to return one level up

~~DISCUSSION~~