The MX55 is one of the semi-pro reel-to-reel machines made by Otari. The machine implements robust construction but the signal path is very complicated full of op-amps. This article describe the required modifications for the improvement of the playback and recording. The preliminary work is based on: full rebuild of the mechanism – cleaning […]

Introduction    The Dragon model made by Nakamichi is one of the top cassette decks and it is unique with its playback auto azimuth correction system which improves the high frequency loss due to the azimuth errors in the records. In the past several years we serviced around 10 machines and made full rebuild of […]

   Some experienced technician claims that the reference level specified in the service manual was wrong listed for all the Tandberg 3014A models. The service manual specify 580mV at the Dolby chip test points (TP4) when using standard Dolby test tape like Teac MTT-150 (400Hz-200nWb/m ANSI). The Tandberg level test tape is based on 1kHz/250nWb/m […]

Part 1 – Introduction    It is a post commenting repair & upgrade process of one interesting cassette deck. I will make a detailed review of this model due to its unique circuit design (reduced use of negative feedback stages). The idea was to repair some problems, calibration, replacing the old parts that grow old and […]

   Engineers from the Laboratory of Embedded Systems started a project for development of contemporary Reel-to-Reel tape deck. GOALS IN THE PROJECT    The intention of this project is to build a technology for manufacturing of contemporary reel-to-reel tape player (tape deck). Why analog reel-to-reel tape player? Why not cassette deck? Maybe you know that […]

   Phase compensation is a method for correcting the time problems on spectrum in magnetic audio recording. These compensation networks are provided for the record amplifier circuitry, also for playback amplifier. These networks enable the circuit to be optimally compensated for group delay introduced by the record equalization circuitry with separate adjustments for both operating speeds. The result […]

  What’s New: 10 Jan 2019: adding Sony TC-K777 (MK1 – Sendust head), Nakamichi 680ZX, Alpine AL85 09 Dec 2017: adding Technics RS-B905, Aiwa Excelia XK-009, Pioneer CT-93, Pioneer CT-S830S charts; 01 Oct 2017: adding YAMAHA K-1020 chart; 28 Aug 2017: adding TEAC V-7000 chart; 27 Aug 2017:  adding a Nakamichi ZX7 chart;    The frequency response of […]

Important!: The laboratory discontinue the partial repairs of cassette and reel tape decks from the JAN 2021. From JAN 2023 we support only full restoration process! We cannot process international request outside EU and cannot process machines more than 30 kg weight (the international sending of heavy parcels and machines from Bulgaria is limited!). For […]

  The service center is situated in Plovdiv – Bulgaria. Bulgaria is a small country in the European Union and Plovdiv was the European Capital of the Culture in 2019. The laboratory specialize analog magnetic recording in parallel with the research on the embedded systems and electronics. About the magnetic recording It is very important […]