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Thread: Tascam 388 Transport Trouble

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    Tascam 388 Transport Trouble

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    I know I know...you've heard this problem before...

    First time poster, long time lurker...

    I've worked on and fixed 3 other 388s in the past 10 years or so, but this one I just grabbed has me stumped. Trying to save it from being scrapped and pass it along to my singer...

    I realize transport problems are common, but I believe I have taken a swing at the most common fixes, see below.

    So seeking other troubleshooting tips.


    Basically you hit play, it engages then immediately stops. FF and RW do the same, often going "limp" after engaging (insert joke) and becoming loose in the path, coming off the guides.

    Friday night I had FF working, but I seem to have adjusted it to where it isn't right now. In fact, ff was working so well it was going quite fast (as I was adjusting the speed) that it snapped the tape on the reel as it stopped. I haven't gotten it working again after that. I also occasionally had play going, sometimes if I held the play button down. While playing the right tensioner arm would wobble up and down and the tape would unspool/spool incorrectly (would unspool a lose few inches before the machine would catch up).



    I feel like I should be able to get there with the servo adjustments. I have been adjusting the trimmers on the reel servo PCB to the best of my knowledge (I've done this on other 388s so I know more or less what to expect).
    It doesn't seem that any range of adjustment helps enough to get it to work reliably.

    The behavior that is most odd is that when adjusting R112 and R212 (tension arms), they don't seem to visually move. I'm thinking this may be part of my problem.


    What I do know...

    1. Capstan belt is fine. Turns as it should, I put a new belt on just to be sure.
    2. New manufacture/known good tape loaded.
    3. I went to the hardware store and bought all new fuses. Behavior is unchanged.
    4. I re-seated the reel servo PCB, no change.
    5. When I first opened it, power supply connector "P803" was loose and at least partially disconnected. I reconnected this.
    6. I swapped the reel servo PCB with my other machine, no change.
    7. Tape path has been cleaned (some pieces were very sticky and I took extra care to clean it thoroughly).
    8. I do have the original service book.


    Appreciate any ideas. I have another 388 here that I could swap stuff from if I have to.

    This video I link is not me, but it shows a similar problem, except their tape does not go limp on the tension rollers like mine does.

    https://m.youtube.com/watch?feature=...&v=dfZmoNDUXAM

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    So I've popped top panel off, and loaded my reel.

    I noticed that if I manually release the brakes (as opposed to hitting play) the tape will flow briefly freely until I let go. Perhaps my brakes are locked up or not adjusted correctly? I have never had to adjust the brakes on these, any pointers?

    The left brake has more resistance than the right one. When I push its lever it barely releases.


    Thanks

    Edit: Following service book process I have got the brakes setup uniformly. No change though. :-/



    With my non scientific iPhone level, I noticed each table is a little unlevel (to itself, from left to center to right), as well as tables are not perfectly level to each other. Not talking hugely off, less than half a degree it seems. How far off would they have to be to cause a problem?
    Last edited by kslight; 04-02-2017 at 10:53.

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    Also not sure if worth mentioning, I put it back together and if I press play/ff/RW and manually "assist" either reel, it'll stay running until I stop (or until I fall too far behind pace).

    As I was doing this I noticed that tape threading through the left side binds slightly just before it enters the reel.

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    Still sounds like it may be the brakes. Are there any more brake adjustments???
    We've got bush,We've got bush!!!

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    img_3651-jpg

    As far as I can tell from the service procedure, this is adjusted correctly. However I've never messed with the brakes on a r2r before, so I could be mistaken. Here is the procedure and diagram.
    img_3658-jpg

    There is still a significant range I could move screw A up or down on the left or right brake which could widely open or restrict further the felts. Right now both sides are adjusted more or less to open identically. I didn't take a picture of this while I had it apart. I put it back together temporarily just to clean up and be sure I didn't lose the screws...

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    You are clear that anytime you are adjusting these types of brakes there are 4 adjustments to make, yes? counter clockwise and clockwise for both reel tables, and the tension is different for each table in the counter clockwise and clockwise directions. I assume you are using a reliable spring scale to make your adjustments?

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    To clarify, The only brake adjustment I made was per Step 1, section 1-3-2 (shown in the photo). I adjusted screw A on the left brake so that lever C is parallel to the solenoid. When I first pulled the panel off, I noticed that it was not parallel, and made a small adjustment, but left everything else as is.


    I don't own a spring scale (recommendations?) to do the full adjustment, and I wasn't really sure that brakes are the issue as I've never experienced this exact problem before. Was hoping for someone to chime in with what I should troubleshoot next.

    I'll have more time this weekend hopefully, to post a video to be more specific.

    Thanks

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    https://m.youtube.com/watch?feature=...&v=lL0uWGxR4Bc

    Very short video (one handed, sorry) illustrating the transport problem.


    Thanks

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    "Basically you hit play, it engages then immediately stops. FF and RW do the same, often going "limp" after engaging (insert joke) and becoming loose in the path, coming off the guides".
    You have lost the " 15 v nst supply". There is a 35v 300 ms pulse that energizes the capstan/brake solenoids.It ramps quickly down to a 15v "run" voltage.It could be as easy as a blown fuse-check them with a ohm meter not just visually- or a problem in the 15 v section of the power supply PCB.

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    Question:

    You refer to connector P803. To save me the time of having to hunt all over the schematics can you tell me what to board that connector is mounted?

    I watched the video. The reels are turning the wrong way when you hit play. I'm not certain if that's because there is a logic problem or something is wired incorrectly, or something else...not sure if the reels spinning the wrong way is because the logic is telling them to do that, or if they are turning the wrong way because they can't do otherwise and that's allowing the tension arms to drop in which case they *would* start to turn the wrong way. You probably realize this, but when you hit PLAY the supply reel should turn clockwise to provide holdback tension, and the takeup reel should turn counter-clockwise to provide takeup tension. They are both doing the opposite of what they should do when engaging PLAY which is allowing tape to slack on both sides...tension arms drop triggering the transport shutoff.

    So what happens if you have a buddy manually support the tension arms to about the mid-travel position and you hit PLAY? Can you put up a video of that?

    Other questions:

    *Do you know any other history of the unit?
    *Can you contact the seller and ask if it started suddenly or if there were symptoms that came on gradually?
    *Any known trauma sustained by the unit?
    *Were you aware of this issue prior to purchase?

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