Servicing a SONY DAT machine (Pictorial)

Discussion in 'Tape' started by SaSi, Sep 17, 2008.

  1. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    Ok

    Once tape loaded ("open/close", no "play") try to rewind and fast forward.
     

     

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  2. redjr

    redjr AK Subscriber Subscriber

    Messages:
    552
    Location:
    Danbury, CT
    Even if I just put in a tape and hit close(no play), it loads the tape, but does not engage the pinch roller. No rewind or fast forward. Even if I do nothing, it goes to CAUTION. So this would indicate something is not engaging correctly with simply loading a tape. No? With no buttons pushed.

    Question: If I simply load a tape and push Close, should the tape still be extracted from the cassette - even if Play, Stop, or any other key has not pressed? Or, does DAT 'get the tape ready' for the other functions.

    Correction: Even if I don't press play after loading a tape, the pinch roller engages with the capstan, but the capstan is not rotating. Now it seems more like a logic issue. I hope it's more simple than that.
     
  3. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    If you simply load a tape and push "close", the tape will be extracted, the drum will spin, the pinch roller will engage the capstan, the capstan will rotate forth AND back (~1 second) and the ABS time will be readen (then everything stops for standby).

    So your capstan may have a problem. May be it is just stuck (but you need to "open" the transport to rotate it from the inside), or there is a power/logic problem.

    Another test to run: remove the pinchroller (be careful of the tiny white washer that holds it) and try to play/rewind/fast forward (just to check the spool motor).
     
  4. redjr

    redjr AK Subscriber Subscriber

    Messages:
    552
    Location:
    Danbury, CT
    Yes, the capstan motor does move freely from the back. After reading your dismantling instructions in another earlier post (#600), I think I'll try and separate the two basic halves of the transport and have a look inside (tomorrow evening). If I get that far, I'll take some photos. I took the underside PCB off, to check the capstan, but beyond that, it doesn't seem like there's anything to service/clean under it. I re-assembled it. I presume that doesn't need to be removed to separate the halves? It seems that member RMbA whom you were helping a few pages back has similar/related issue(possibly more severe). I have not removed the pinch roller and done that test.

    It's surprising this transport holds together as well as it does for a consumer product, but as we all know it has issues. The Japanese are a marvel with their delicate and miniature design and engineering. What they did with the TCD D3 that I have was incredible. That's the next one to get fixed. :) I really hope I can this unit working. You're knowledge and assistance is greatly appreciated.
     
  5. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    I am surprised that you managed to check the capstan from the back without separating in halves.

    However to separate the halves you don't need to remove the underside PCB. It can stay attached to the lower half. Just remove its 2 screws located in the angle at the back as they are connected to the upper half.

    Also check the condition of the loading gears (the red circles in post #600). It could be the culprit.
     
  6. redjr

    redjr AK Subscriber Subscriber

    Messages:
    552
    Location:
    Danbury, CT
    I've separated the 2 halves and this mech is clean and dirt free. No gummy grease, no missing or chipped gears, everything seems to move smoothly. I've attached some photos. Not sure what I'm looking for, but nothing looks out of place.
     

    Attached Files:

  7. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    On picture P1000630: the washer on the black gear with an arm is ready to fall. Put it back on place, and put a tiny drop of locker (nail paint) on top of both.

    On picture P1000628: check that the gear assembly on the upper left rotates freely. With you thumb, give a kick on the black gear surfacing the front of the transport. The assembly should rotate with some inertia. If not, remove the upper black gear (screw), the white one underneath, and clean shafts and axles.
     
  8. redjr

    redjr AK Subscriber Subscriber

    Messages:
    552
    Location:
    Danbury, CT
    Done. Re-seated the gear clip and checked the gear assembly in front. Now I can understand why so many of those work free. No tactile click when you put them on. Seems like a bad design for a moving gear that it's holding on. The gear assembly run freely with a little inertia. Just seems like a switch is not being activated properly, due to age or something else.
     
  9. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    I would still remove and clean the gears, by security.

    There are 2 switches (SW1 SW2) that control the loading sequence. They are upside down on a small pcb located on the lower right corner of the transport (together with the rec & cas in switches). You can try to spray deoxit.
     

     

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  10. redjr

    redjr AK Subscriber Subscriber

    Messages:
    552
    Location:
    Danbury, CT
    Switches 1 & 2 were the first switches I Deoxit'd. Will clean the gears tonight.
     
  11. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    Hi

    Any news ?
     
  12. redjr

    redjr AK Subscriber Subscriber

    Messages:
    552
    Location:
    Danbury, CT
    Hello,

    No. Haven't had any time to get back to it. I'm going to Deoxit the 2 pin switches again on the small pcb probably this weekend.
     
  13. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    Any news ?
     
  14. redjr

    redjr AK Subscriber Subscriber

    Messages:
    552
    Location:
    Danbury, CT
    No good news. I'm still perplexed as to what else I can observe/test. It's still on my bench, but I'm frustrated at the moment. It may be beyond my level of knowledge to trouble-shoot and not very many places - if any - in the US that could repair it.

    If you have any more ideas, I'm open, just less enthusiastic at this point.
     
  15. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    Did you clean the gear shafts ?
     
  16. PaulvtH

    PaulvtH New Member

    Messages:
    1
    I have a problem with my Sony DTC-690 trying to load the tape. I took apart the running gear as described and checked several things, but it acts still the same. The tape is pulled out of the cassette by the tape load arms (sometimes three times in sequence). Then the arms return to the home position, the tape is still extracted. The video shows the described situation:

    Anyone who is recognizing this behavior?
     
  17. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    The head-drum should rotate as soon as the cassette is loaded. Check connectors.
     

     

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  18. Razvan02

    Razvan02 New Member

    Messages:
    3
    hello guys.

    i just recorded a 5 hours long ( i guess) HP dds tape on a sony dtc 670 dat machine and everything went smooth up until the end and the deck would not eject the tape. At a further inspection, upon opening the unit i was able to get the tape out and do some more tests.

    It seems that the capstan motor is vibrating at a constant rate forward and backwards right after the unit is turned on and then nothing. Deck freezez and by restarting it, the capstan motor restarts vibrating. I consulted the schematic diagrams and it seems that q302 might be the problem. or ic01 or ic316.

    Have you seen this problem before ? Any hints ?

    Thanks for any useful information!
     
  19. hdrobien

    hdrobien Active Member

    Messages:
    473
    Location:
    France
    Can you be a little more specific about the "vibration" ?

    Are you sure it is the capstan ? Look at the pinchroller to check its steady rotation

    Could it be the take up or supply reel rotating "jerky" ?

    Btw DDS tape are not fully compatible with audio DAT unless you stick to DDS1 and 60 meters tapes (60 meters = 120 minutes).
     
  20. Razvan02

    Razvan02 New Member

    Messages:
    3
    pinch roller also vibrates near the end of the pathway. that is: a short move back then forth toghether with the capstan motor, but pinch roller does not rotate. the arm itself is vibrating. pinch roller does not touch the capstan. i don't know how to describe it. its like shaking from a fever. 1 - 2mm back then forth and so on. frequency is around 30, 40 hz. supply and take up wheel do not move at all.

    it goes like this: inserted tape, tray closes, does not load the tape - not even trying - then this shakking occurs without the take up or supply reels spinning. deck is unresponsive to all commands. after switching off and on again: head is rotating, shakking of capstan and unresponsive again. i am thinking that the control logic failed in some way. that might explain the unresponsiveness. or it might be the motor itself stucked in a weird possition. dds tape was quite hot after 5 hours of recording. Deck was working just fine before using this dds tape which i know it's not compatible, but i said to myself: what the heck: i'll repair it if it goes wrong and it did :)
     
    Last edited: Apr 22, 2018 at 2:54 AM

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