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Thread: Mint Revox B77

  1. #21
    Join Date: Aug 2012

    Location: Hartlepool UK

    Posts: 1,466
    I'm Alan.

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    Tape Deck Control Board
    This board came with an additional DIY board that had been patched into it
    Turns out this add on board is to change the momentary Pause function to a latching pause function
    I didnt like this bodge up so I disconnected it.
    Turns out you can actually get a plug in board that does the same thing from Revox online so I have ordered one of them, looks a much more professional option
    https://www.revox-online-shop.com/zu...pause-77-r0023

    IMG_2246 by Alan Towell, on Flickr

    IMG_2247 by Alan Towell, on Flickr

    IMG_2253 by Alan Towell, on Flickr
    Turntable - Garrard 401/Jelco 750L/Ortofon Kontrapunkt B, Pioneer PLC 590, SME 3009/2 , Denon DL103R - DIY Paradise Phono stage - Reel 2 Reel Studer A810, Otari MX55,Tascam BR20 - Digital HTPC / Young Dac - Preamp - DIY B4, 821, Power Amp's DIY Voyager Mono Block, Speakers Tannoy precision 6.4 / Wilmslow Kit Volt BM220.8 / Scanspeak D2905/9500

  2. #22
    Join Date: Aug 2012

    Location: Hartlepool UK

    Posts: 1,466
    I'm Alan.

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    Been doing some more work on my B77 recently to resolve a few issue’s
    I was getting a regular wow from it that I put down to the capstan roller wheel as it was a bit tired but when I got a new one the problem was still there after cleaning the whole tape drive. I thought it might be some oscillation from the capstan drive motor board so I checked out the electrolytics I recapped this board with and they were just general purpose ones from a A77 service kit I bought a while back but they had very low ESR, so I decided to change them back to some new AVX tantalums that I had and this has cured the problem.
    Capstan drive board by Alan Towell, on Flickr
    Turntable - Garrard 401/Jelco 750L/Ortofon Kontrapunkt B, Pioneer PLC 590, SME 3009/2 , Denon DL103R - DIY Paradise Phono stage - Reel 2 Reel Studer A810, Otari MX55,Tascam BR20 - Digital HTPC / Young Dac - Preamp - DIY B4, 821, Power Amp's DIY Voyager Mono Block, Speakers Tannoy precision 6.4 / Wilmslow Kit Volt BM220.8 / Scanspeak D2905/9500

  3. #23
    Join Date: Aug 2012

    Location: Hartlepool UK

    Posts: 1,466
    I'm Alan.

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    I was never very happy with the corrosion on the main audio switch board so when I seen a decent one come up on ebay for £20 I bought it and switched it over, this board was in very nice condition and had metal film resistors to was a recent version
    Basis boaerd 2 by Alan Towell, on Flickr
    Basis board 1 by Alan Towell, on Flickr.
    Turntable - Garrard 401/Jelco 750L/Ortofon Kontrapunkt B, Pioneer PLC 590, SME 3009/2 , Denon DL103R - DIY Paradise Phono stage - Reel 2 Reel Studer A810, Otari MX55,Tascam BR20 - Digital HTPC / Young Dac - Preamp - DIY B4, 821, Power Amp's DIY Voyager Mono Block, Speakers Tannoy precision 6.4 / Wilmslow Kit Volt BM220.8 / Scanspeak D2905/9500

  4. #24
    Join Date: Aug 2012

    Location: Hartlepool UK

    Posts: 1,466
    I'm Alan.

    Default

    I was also getting some intermittent output fro m the left channel and I traced that to the poor quality RCA sockets which were loose and tarnished.
    The RCA plugs on the A77 and B77 are crap and too close together to get the plugs in properly so I bought a set of replacement ones from Revox online in Germany. Fitting was straight forward but yo have to do some work with a round file to accommodate the extra spacing in the new circuit board
    I also did away with the 5 pin din radio socket wiring as it was also knackeered.
    I changed the 2 output pots for a couple of Sfernice P11S ones I had form a passive pre amp.
    This cured the intermittent output so sounding much cleaner now with even channel balance.
    Before
    Old in out board by Alan Towell, on Flickr
    In out board 2 by Alan Towell, on Flickr

    After
    In out board by Alan Towell, on Flickr
    New RCA Board by Alan Towell, on Flickr
    IMG_2456 by Alan Towell, on Flickr
    Turntable - Garrard 401/Jelco 750L/Ortofon Kontrapunkt B, Pioneer PLC 590, SME 3009/2 , Denon DL103R - DIY Paradise Phono stage - Reel 2 Reel Studer A810, Otari MX55,Tascam BR20 - Digital HTPC / Young Dac - Preamp - DIY B4, 821, Power Amp's DIY Voyager Mono Block, Speakers Tannoy precision 6.4 / Wilmslow Kit Volt BM220.8 / Scanspeak D2905/9500

  5. #25
    Join Date: Aug 2012

    Location: Hartlepool UK

    Posts: 1,466
    I'm Alan.

    Default

    My record board didn’t have the muting circuit board so again I picked a one up from ebay and fitted it
    Whilst I had everything apart I also changed out all the carbon film resistors directly in the signal path for Takman Rey metal films on the input, record and reproduce boards
    Muting circuit board by Alan Towell, on Flickr
    Turntable - Garrard 401/Jelco 750L/Ortofon Kontrapunkt B, Pioneer PLC 590, SME 3009/2 , Denon DL103R - DIY Paradise Phono stage - Reel 2 Reel Studer A810, Otari MX55,Tascam BR20 - Digital HTPC / Young Dac - Preamp - DIY B4, 821, Power Amp's DIY Voyager Mono Block, Speakers Tannoy precision 6.4 / Wilmslow Kit Volt BM220.8 / Scanspeak D2905/9500

  6. #26
    Join Date: Aug 2012

    Location: Hartlepool UK

    Posts: 1,466
    I'm Alan.

    Default

    So after all this I calibrated the deck for RTM LPR90 tape and the frequency response form it is within +- 1 db and it sounds really good
    Here is a short video of the calibration check after adjustment, input was from an NTI Minirator MR Pro signal generator and the output was monitored with a Leader 186A dual channel AC Voltmeter all set for -10dB


    https://www.youtube.com/watch?v=t5GNxtpHkMA
    Last edited by 337alant; 23-06-2019 at 18:04.
    Turntable - Garrard 401/Jelco 750L/Ortofon Kontrapunkt B, Pioneer PLC 590, SME 3009/2 , Denon DL103R - DIY Paradise Phono stage - Reel 2 Reel Studer A810, Otari MX55,Tascam BR20 - Digital HTPC / Young Dac - Preamp - DIY B4, 821, Power Amp's DIY Voyager Mono Block, Speakers Tannoy precision 6.4 / Wilmslow Kit Volt BM220.8 / Scanspeak D2905/9500

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