MSR-24S Speed Problem

Discussion in 'TASCAM DIY Repairs and Mods' started by Thomas Körffer, Mar 27, 2021.

  1. Thomas Körffer

    Thomas Körffer New Member

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    From:
    Germany
    Gear:
    TSR-8, MSR-24S, MSR-16S
    Hallo all and greetings from germany...
    today i picked up a TASCAM MSR-24S in nearly new condition.
    Heads and Parts are in a great condition

    Now the problem...

    it seems the machine runs on half speed as usual...

    So switched to high Speed it runs with not as usual 15ips and only on 7.5 -
    switched to low it runs on a very slow speed - seems to me half of 7.5ips
    So the whole system speed is half as normal.

    Also the Pitch Control does not infect the capstan.
    The Pitch change can be read in the display but with no changed to the speed.

    Regarding the Service Manuel it seems there is an oscillator controlling the speed.
    I found a User in the Internet with Same issues on a 24S.
    Unfortunately he did not say anything about the Solution.
    But he fitted it without the Service Manuel by helping from a radio shack guy.

    Any help for me?

    Thanks and stay healthy

    Thomas
    Last edited: Mar 28, 2021
  2. SkywaveTDR

    SkywaveTDR Well-Known Member

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    Hi Thomas,
    It might be that for whatever reason they made units that were half speed and the solution is normally a pulley and belt change. People that look at speed controls do not know what they are doing as changing a resistor will not get you the right speed. These motors are made to run at a range of speed and that range is extended by the use of the pulley on the capstan motor and when you put a different pulley them most the time you need a different longer belt. So you need to be careful when buying a unit as the S at the end might mean slow or it might mean Dolby S.
    The 238S is not an easy deck to repair due to the Dolby S cards in it and they are expensive.
    The BR20 had a slow model and a regular model- difference is? Motor pulley. The 22-2 is a 15 IPS deck and the same transport as a X3 or X300. How does it go faster with the same motor? Larger Pulley. I have BR20 large pulleys I have had made up and I sell them when needed. I have never dealt with your problem but if you can order the correct larger pulley for the capstan motor from Tascam it might be as easy as that. It would be the larger pulley not the smaller one if both are listed.
  3. Thomas Körffer

    Thomas Körffer New Member

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    Gear:
    TSR-8, MSR-24S, MSR-16S
    Hey, thanks for your post.

    So first let me say. I know the MSR24S because I have all other MSR-S Modells too in my Studio. Also I have an BR-20T.

    So the S ist definitiv for "Dolby S" and not for slow. I think there is no speed changing option.
    Also, there is the problem with the not working Pitch Change Control -
    this confirms that there is an error.

    In the internet I found a user with the same problem, that asked for the service manual.
    But the gets help by an older radio stack technician. So the problem is not a big I hope...
  4. SkywaveTDR

    SkywaveTDR Well-Known Member

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    OK, You have to be careful in that some people put the wrong over tight belt on units. This will upset the speed and then some decks have sticky and decaying pinch rollers as well as bearings that have not been oiled for 30 years. I have a MSR24 here to work on but have not opened it up yet- it is so heavy to get to my bench it is not making me rush to it.
    The problem is to define the problem correctly you need a speed tape which is a subset of the alignment tape otherwise you don't really know what is what as you have no reference to go by.
    The 1" format is not the easiest to deal with when working on them.
  5. Thomas Körffer

    Thomas Körffer New Member

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    Gear:
    TSR-8, MSR-24S, MSR-16S
    I know the 1" format is shit. I have the Fostex G24S also.
    I also have an MRL Tape for the 1".
    So I know it run exactly the half speed.

    Regarding the Shematics it says...
    The capstan motor is controlled using the 9.6 kHz reference which is obtained by dividing by 512 the frequency signal from a quartz oscillator.
  6. Thomas Körffer

    Thomas Körffer New Member

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    Gear:
    TSR-8, MSR-24S, MSR-16S
    I wonder if here are some good technicians which know the MSR-Models... which can give me a hint...
  7. Thomas Körffer

    Thomas Körffer New Member

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    TSR-8, MSR-24S, MSR-16S
    Solved it...
    -mjk- likes this.
  8. -mjk-

    -mjk- Moderator Staff Member

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    DP-32, | 2A Mixer, A3440
    @Thomas Körffer we would appreciate it if you could find the time to detail the solution for the forum. Thanks.
  9. Thomas Körffer

    Thomas Körffer New Member

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    … it was a bit confusing, it took me three hours to find it.
    And you need… a frequency counter. Without it, your lost!

    First, as I opened it, I saw, that something was happened to the capstan control board.
    I had to clean it fully. It was completely suffered with some strange material.
    Maybe Beer or Coca Cola :)

    After cleaning it i put it back in and see that the pins on the board where the power comes on, has to be re-soldered. But that was not the fault.

    I checked all supply voltages. Everything was OK there.

    Then I startet to figure out how the servo and the frequency works.
    As I set the Speed jumper to High, the machine runs on 15 IPS.
    But this could not be the Solution (to set it higher to run the required speed)

    So for my understanding from the schematics, they generate a CS-Signal (Capstan Speed Signal) on the Control PBC. This can be influenced by the Speed Dip Switch.
    From the Control PBC the CS Signal gets to the Servo Control Board.

    The Capstan is connected to the Captan Control Board and delivers a Back-Signal, that tells the Control-Board, on which speed he is running.
    Also… the Capstan gets only a power signal which let him run in a low speed.
    Adding the CS-Frequency Signal, generated from a Oscillator on the Control-Board and affected by the pitch control, the speed jumper and other things the CS-Signal is delivered to the Capstan Control PCB.

    The CS Single on the Output of the Control PCB was OK.
    On the Output to the capstan this signal was missing.
    So the fault must be on the Capstan Servo PCB.

    I changed the component where the Signal gets in and don't came out of of it (0,75 €) and everything was fine again.

    Then I figure out, that the Dip Switch set to High - the machine goes up to 30 IPS.
    Same on the MSR-16S - which is controlled the same way.
    -mjk- likes this.
  10. -mjk-

    -mjk- Moderator Staff Member

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    Thank you for taking the time to document that! Cool story. So now you pretty much know all there is to know about running speeds on that model.