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Sony TC-651 Slowing down to an audial crawl in reverse. Advice?

Discussion in 'Tape' started by IanMcI, Dec 30, 2017.

  1. IanMcI

    IanMcI Active Member

    Messages:
    333
    Location:
    San Mateo, CA
    I picked up a Sony TC-651 at an estate sale in superb condition (despite its age). I've gone through it to some extent - lubrication of obvious points, replaced brake shoes...

    It played great! And still does, it appears, in Forward Mode, but I only just today tried it in reverse, and while it was humming along perfectly, it began to slow to a crawl; again, this was in reverse; it still seemed to play well in Forward. In reverse, it would slow, then, after pressing the stop button and starting, would play well for a few seconds, then slow again, eventually to a stop.

    Any ideas what might be causing this? I've been into the guts for the lube job and replacement of brake felt, but didn't see anything that would suggest any impending problems.

    Motor issue?

    Anyway, just hoping someone of you might have a direction I might go.

    http://www.audiokarma.org/forums/index.php?threads/sony-tc-651-help-with-feed-reel-brake.801838/

    Ian
    SF Bay Area
     
    Last edited: Dec 31, 2017

     

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  2. IanMcI

    IanMcI Active Member

    Messages:
    333
    Location:
    San Mateo, CA
    A day later now: and I took the face plate off, thinking I might notice something amiss when playing.

    Again, when playing in reverse, it eventually slows to a stop. I do notice that it isn't anything slipping, rather the motor itself slows to a stop.

    I checked for drag in the system by pulling tape through, but didn't notice anything unusual.

    Again, plays well in Forward. I'm stumped. And it's otherwise a very nice unit and sounds great.

    Ian
    SF Bay Area
     
  3. DaveInVA

    DaveInVA New Member

    Messages:
    37
    I would check the condition of the pinch roller rubber. If it has hardened up that could cause the problem. As the capstan is not centered it may be having trouble pushing the tape through the heads when it is pulling in normal play.
    When it stops check and see if the metal capstan is still turning. If not then its the capstan belt slipping which if original may not be in great shape.

    Dave
     
  4. IanMcI

    IanMcI Active Member

    Messages:
    333
    Location:
    San Mateo, CA
    The pinch-roller rubber seems to be fine. I have the face plate off and can see most of the works. Pinch roller and capstan move easily enough, and the motor drive wheel moves freely when moved manually. I see no evidence of slippage or binding. No grinding, no sense that anything is binding on the motor, or impeding it in any way when turned manually.

    What I do see is the motor drive slowing down (almost imperceptively, as it doesn't require much slowing down to hear the effects), and at times coming to a full stop. It doesn't matter where in the tape this happens (though, again, only in "reverse", that is, when the tape is playing off the right-side reel).

    The capstan belt looks to be good and is not slipping - again, it's rather that the motor itself is just plain slowing down and at times stopping completely.

    When it does slow down or stop, it isn't as if the flywheel is carrying things on for a few inches, the motor will "play" at that slow speed for minutes at a time, or will slow to a stop over about thirty seconds at times - it seems to vary somewhat.

    Ian
    SF Bay Area
     
  5. DaveInVA

    DaveInVA New Member

    Messages:
    37
    It could be the motor run cap has dropped from its stated value. Could also be the motor needs to be taken apart and cleaned and lubed.
    I would also clean not just the heads but all the guides and anything else the tape touches. Any extra friction can cause problems.
    How many tapes have you tried? Sticky shed tapes could cause this also.
    I would also check the back tension of the right hand spool motor and see if its set to high. Its a wire wound resistor with a sliding clamp adjustment.
    Also be aware that these units need the relay snubbers replaced or they WILL let the magic smoke out. Very common failure on these. This probably doesn't have any bearing on your current problem but it will happen sooner than later, guaranteed

    Dave
     
    Last edited: Dec 31, 2017
  6. IanMcI

    IanMcI Active Member

    Messages:
    333
    Location:
    San Mateo, CA
    I suppose this is more a labor of love than I expected to get into. I've had a ball with some tapes from the era of when this machine was made and they sound great. I guess I can just play it as it plays best - in forward mode, reversing the tape on their spindles, rather than playing in "reverse" for side 2.

    Your pointing out a possible issue with a motor run cap seems like a reasonable conclusion, given the circumstances. I'm pretty sure I won't be getting into testing for and replacing that.

    But I do thank you, DaveInVa. Valuable info, and a learning opportunity!

    Ian
    SF Bay Area
     

     

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  7. audiojones

    audiojones Jonesin' for audio Subscriber

    Messages:
    7,184
    Location:
    Central NJ
    Not the motor run cap but most likely the spark quenchers (the snubbers that Dave mentioned) for the motor direction change relay. When a spark quencher (which is a little plastic box containing a resistor and a capacitor wired in series) goes bad it usually starts to conduct electricity. This is bad because the spark quenchers are wired across the contacts of switches and relays to absorb the nasty arc that forms when contacts make and break. When the quenchers go bad and start conducting across switch terminals that are supposed to be open it makes the motor try to do two things at once (run at high and low speed or in forward and reverse simultaneously etc) which of course it can not do.

    Most reversible open reel decks have a board with all of the spark quenchers mounted on it, and when a quencher goes bad you can usually see its plastic box bulging out at the sides. I have run into the same exact symptoms you are describing a number of times with decks by different manufacturers and each time it has been a bad spark quencher. At first everything runs ok but as the bad quencher heats up it breaks down and causes the motor to fight itself between two functions, causing the motor to slow down and eventually stall out. When it cools down it'll work ok but then it will act up again as it heats. In forward there is no problem because that's probably the bad one that is breaking down when the deck is in the reverse mode (in other words in reverse the motor gradually tries to run in both directions as the forward quencher breaks down and starts to conduct).

    Probably best to replace them all but definitely do the ones for speed and direction controls if nothing else. Make sure to get replacements of at least the same or higher voltage rating. The impedance and uf rating can be a bit higher if you can't find the exact one (these don't need to be dead-on like the motor run cap needs to be).

    Should look something like this although Sony typically used orange ones:
    [​IMG]
     
    Last edited: Jan 4, 2018
  8. IanMcI

    IanMcI Active Member

    Messages:
    333
    Location:
    San Mateo, CA
    Thanks, audiojones, not just for the info, but for the way you present it! I'll take a look into these (I've never heard of quenchers). The photo will help ID them, I'm sure.

    Ian
    SF Bay Area
     
  9. DaveInVA

    DaveInVA New Member

    Messages:
    37
  10. TC 651 fan

    TC 651 fan New Member

    Messages:
    4
    Dave, saw your post here to Ian regarding his slowing down problem. I have an old TC 651 that I was gifted along with 30 some odd tapes; some recorded by the previous owner along with a number of pre recorded tapes!! I have an old TC 440 that I bought new in '72 so I was familiar with loading and running a tape and was ecstatic to discover that the old tapes, on the 651 sounded fantastic and the machine actually ran and preformed well. Knowing that the belts wouldn't run for ever, I found some replacement belts, installed them as well as replaced the brake pads. After cleaning the heads and the full track of the tape, I discovered that I had the same problem as Ian, in that in the rewind mode (right to left reel) the left reel would barely turn... I was convinced that the new brake pads weren't the problem since the tape seemed to function fine in the play mode, in both directions, so I decided it was time to pull the insides out of the wooden box only to discover the PC board with the "spark quenchers" mounted on it, along with the relays, that is EXACTLY like the one you pictured in your reply to Ian. The little orange boxes were mostly in a "swelled up" state, 5 out of 8 of them anyway.
    My main question to you is, what next?? I'm sure if the PC board containing these items along with the relays is available, it's bad expensive. Are the spark quenchers available, individually? I have done some PC board component replacements but not since the days that the TC 651 was new, what '72 or so? Been a while but could probably deal with it for the sake of making the old machine useable.
    Thanks for any help you may be able to provide.
    John (TC651 fan)
     
  11. dhnash

    dhnash Well-Known Member

    Messages:
    551
    Location:
    Wildwood, MO

     

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  12. TC 651 fan

    TC 651 fan New Member

    Messages:
    4
    Thanks too much for your quick response. The prices for the spark quenchers are really great at the site you suggested which makes the possibility that I can get this old machine running again! All I need to do is see if I can summons up the old brain cells to do some precision soldering which I haven't done since 1969 when I was trained as an Army computer repairman with week one (5 days) of the training being soldering techniques/basics...
    I'm excited to find this site since along with the TC 651 deck which I was given, a number of years ago I was also given a TC 654-4 by the owner of Muscle Shoals Sounds Studio in Sheffield, Ala. for partial payment for some photographic work I did for him. It runs in play mode in both directions as well as FF in both directions but I was not able to get any output from the test tape. Decided to take on getting the 651 running right before I dove in on the 654-4 since it played well in both directions. All said, I'll have many questions i'm sure on the 654-4 along with possibly some questions on going through a TC 440 i've had since it was new and have run many miles of tape through it, years ago, until the belts started slipping. Believe a new set of belts and probably some brake pads will get it going right.
     
  13. DaveInVA

    DaveInVA New Member

    Messages:
    37
    The TC-654-4 is basically the same machine except it has a couple extra plug in boards. The 22 pin edge connectors on all the 650,651 654, 850, 854-4 etc like to get brittle with age and crack. I would check and make sure all the plug in boards are seated properly but be careful as the edge connectors break easily. Also check all those connectors for cracks and bulges. These connectors can be replaced with 0.156" spacing 44 pin dual connectors just wire the one side needed.

    Dave
     
  14. dhnash

    dhnash Well-Known Member

    Messages:
    551
    Location:
    Wildwood, MO
  15. TC 651 fan

    TC 651 fan New Member

    Messages:
    4
    Man, what a great resource this site is! Thank you too much for the info on such an archaic music machine! I would have never thought there would be so much information out there for such old audio equipment!
    I had thought that I would complete the work on the 651 before i started on the 654-4 but with your comment on them both being similar machines, the 654-4 may have the same problem with the spark quenchers. So i've decided to dive into it before i order the 8 cap-resistors (right?) for the 651 in case i may need the same thing for the 654-4. It of course needs a belt kit along with brake pad over haul also. I'll take a look at the plug in boards as you've suggested also. I'm a bit challenged at the idea of having to replace the card edge connectors but we'll see what that looks like also.
    I have a question on, what about observing polarity on replacing the spark quenchers. I've identified the position of the original components, with which side has printing on them but don't know how to identify how the replacements should be positioned. Not knowing much about "electrical theory", I thought this may make a difference. Great comment (Dave, i think) on a previous reply regarding the function of these spark quenchers, comparing them to the capacitor on the old breaker point distributors on cars, turned the light on for me.
    Thanks again folks!
     
  16. dhnash

    dhnash Well-Known Member

    Messages:
    551
    Location:
    Wildwood, MO
    As far as I know the spark quenchers are AC rated and are not polarity sensitive. If you would like, you can install the new ones with the labeling oriented that same way as the original ones.
     

     

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  17. TC 651 fan

    TC 651 fan New Member

    Messages:
    4
    Well, i've been successful in changing the spark quenchers in the TC 651 and reassembling the relay board. So it goes, it still runs at a creep in reverse (fast) mode. It functions well in FF and plays fine in both directions so I suppose I can live with it as is and simply swap the reels if fast winding is necessary. I'm happy to have been advised to replace the "swollen" cap-resistors since it was obvious they were going bad. Thanks for that information as well as where to find the components needed.
    I did find a couple of these same components in the TC 654-4 when I checked it but since they were on boards that were much more difficult to access, decided repairs on this machine are beyond what I want to get into.
     

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