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Thread: Studer A807 - Tension adjustment for smaller reels

  1. #1
    Junior Member
    Join Date
    Feb 2014

    Cool Studer A807 - Tension adjustment for smaller reels

    Hi everyone,

    This is my first post on this forum and would like some advice please and technical help. I have posted this thread on similar forums but so far had no help so I thought I post it here too

    I have 2 Studer A807s, MK1 with VU meters on board and a MKII with meter bridge and on both experience harsh braking when using 7 inch reels and smaller. I know that these machines are not so suited in handling nonbackcoated tape especially on cine center reels however I wonder if there has been any modifications that have been done to the electronics so they can handle LP tape a little gentler? I don't think it is a case of misalignments from my part. I believe years ago, a technician from Studer in Switzerland mentioned to me some modification that can be done so the back tension can be reduced for using smaller reels. I find them a little aggressive when stopping a fast winding tape by reversing the direction and can damage the tape.

    Also I note that when using 7 inch reels and am starting to wind a tape from let's say a 3/4 full reel to fill it up completely, the machine does not pick up the full winding speed but for a few seconds it winds at a slower speed and then kicks in to the fast speed. Is this normal?

    I hope that I can get some feedback from you experts out there so I can keep my machines up to spec as much as possible. The sofwares I have are the following:
    MKI: 10.89
    MKII: 06.90

    Many thanks

  2. #2
    Member Sponsor [WBF Founding Member]
    Join Date
    Apr 2010
    Hang on as Ki our resident Studer guy is travelling Sure JDZA and a few other might also have a few ideas as will some others here.

  3. #3
    Junior Member
    Join Date
    Feb 2014
    Brilliant . many thanks. I shall be looking forward to some suggestions to improve my machines as I would like them to be gentle with smaller tapes too if I need to make a transfer or listen to something that is vintage from my collection without ending up tearing the tape.

  4. #4
    The 807 was the last 2 track machine Studer built. Unlike the previous generation tour de force A810/ 812/820( or even the earlier A 80 and the lowly A67/B67) tension is only controlled on the supply side by conventional swing arms with Studer claiming adequate electronic control alone on the take up side for the 807.How much of that was true progress and how much cost cutting on a dying medium from a gasping corporation is difficult to say (vide A820 multitrack vs A 827).The cynical may speculate that the A 807 was more Revox than Studer in design philosophy.

    All this is just along winded way to say that the 807 may well not be as gentle on tape tension as previous Studers and more resemble the Revox machines in that regard. Answers could possibly be found in Fred Thal's old Studer list archives.These are an incredibly valuable source of information with even Studer engineers and some extremely experienced people weighing in. Postings by "hobbyists" like us were seriously frowned upon .Search for a link to these archives on the Tape Project forum. Not to be confused with the current Studer list.

  5. #5
    Member Sponsor Addicted to Best!
    Join Date
    May 2010
    Seattle WA area
    Although the problem was described as "harsh braking," the issue might be with your capstan start and stop timing in respect to your pinch roller engaging and disengaging.

    Studer published a service bulletin for mod to take care of this issue with SI_112-87_D-D_A807. When capstan holds onto tape by pinch roller action with spooling motors already gone to braking mode, you will see tape loop around capstan. In addition, if you start the machine with spooling motor already taken off and pinch roller engaged but capstan is not coming up to speed fast enough, you will see tape tension going wild.

    I believe above mod that applies to both Mk I and Mk II models will be your first step in fixing the problem.

    As jdza mentioned, the owner of the Studer List didn't consider A807 and A810 worthy of the List and did frowned upon hobbyists asking questions...too bad.

    If you can't access the mod bulletin, please send me a PM.


  6. #6
    Junior Member
    Join Date
    Feb 2014
    A few years have passed since my post however it's never too late. Just an update to post regarding my Studers & tension adjustments for an A807 to be more gentle on less robust tape or using smaller reels. Firstly Studer had published a modification on the Spooling motor board which needs to be carried out ( removing 2 resistors, a diode and a transistor, inserting a diode elsewhere and replacing a resistor with another value).
    The tension adjustments would have to be made from scratch according to the service manual. Having done this I felt it did not improve matters that much. What did the trick was to lower the value of the DC voltage measured on the tension arm circuit board when the arm is at rest! Instead of setting it to 4.0v I set it to around 3.71v or so which is the minimum voltage that it should be set to while watching the stop button led still blinking! If the led stops blinking and shows a steady light then you've gone too far. The machine will not stop spooling at the EOT! Set it to a value where the stop led starts blinking again and seizure the 2 trimpots with a drop of paint. Recheck all tension adjustments for play, ft, rew & shuttle. My 2 A807s are much more gentle now using non backcoated tape . Cheers guys

  7. #7
    Hello Ki Choi,
    It's been a long time since you've posted this comment on A807 "harsh breaking". I was trying to find the service bulletin you are referring to (SI_112-87_D-D_A807), however - no success.
    I would appreciate if you could mail me the copy of it to my mail
    Thanks in advance and best regards,

  8. #8

    A-807 tension.

    Thank you jascha. Had a similar problem with my A-807 continued spooling after rewind completed with rewind motor not shuting down. Came across your post explaining setting tension at 3.71 rather than 4.0 and I followed instructions and solved my problem. Once tape runs out on rewind spool the motor stops. The key for me was the stop button light not blinking. Again thanks.. Reviewing old posts can be helpful ! Hugh

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