Porta One Transport Issues

Discussion in 'TASCAM DIY Repairs and Mods' started by burnt, Aug 18, 2021.

  1. burnt

    burnt New Member

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    been trying to fix up this Porta One i just got my hands on.
    when i unpacked it the heads were engaged
    and i just rotated the big metal wheel and click they disengaged

    at first the FF and RW only worked if i tilted the entire multitrack standing up
    otherwise the RW would not click over
    the FF would work for a second and then get jammed up and stop moving

    PLAY and RECORD worked just fine

    I read thru the service manual and did some internet research
    I sprayed some deoxit in the gear axles. pretty much any gear i could access.
    but focused on the FF and RW gears on the front of the tape transport
    things started improving!
    so I put in a C90 and starting running it FF and RW back and forth
    to work it in the gears and clean & lube things up better
    i sprayed more deoxit in there a couple more times
    and kept working the gears.
    FF and RW working pretty damn good at this point.

    but now sometimes the FF or PLAY does not auto stop when it reaches the end of the tape
    it wants to click over but just doesn't have enough to push it over the edge
    the RW auto stop still works when it reaches the beginning

    and the PLAY functionality is starting to stick again
    and the heads get stuck in the engaged position as well.
    if i hit PLAY and nudge the big metal wheel it clicks and starts to play.
    so seems like that gear is justtt on the edge of playing but not enough to get over the hump.

    i know deoxit is prolly not the best thing to use in this situation
    but it was what i had on hand and figured it was worth a shot.
    when things started working again, i thought i was on top of the world.

    i've been running the tape on PLAY all the way through to the end of hte tape a couple times
    to hopefully work whatever it sticking on the PLAY mechanism free
    i'll prolly do it a couple more times
    also thinking maybe i over deoxit'd things and maybe just needs to dry out for a lil bit.

    if i had to guess i'd say maybe i need to get some better lube or grease
    and try to relube some of these moving parts to get things better?

    what areas should i focus on in regards to the auto stop not clicking over?
    what areas in regards to the PLAY mechansim not clicking over?
    and same for the heads getting stuck engaged when hitting PLAY

    any help of insight is greatly appreciated

    thanks!
    Last edited: Aug 18, 2021
  2. SkywaveTDR

    SkywaveTDR Well-Known Member

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    First, Deoxit is not a oil and while it might work for a while it is not going to long term. There are gears in the assembly that need to be cleaned of old grease that is restricting them from movement. Now that a person was spraying a chemical into areas of the mechanism it is hard to say how that is effecting the drive. Maybe the belts now have deoxit on them. We never did things like this at the factory service and we fixed a lot of them there. Just because you are going to give it a shot does not mean it is correct. Now some Technician will have to use time to clean out the spray you put into it in the wrong place. Deoxit is for contacts not gears. I hear from other guys on occasion how the customer sprayed WD40 in a machines to make it work and the stuff gets all over everything and must be cleaned out in hours of labor that should not have been required. I suspect that what you are doing is going to reverse and the only solution is to clean all that out with denatured alcohol and then start where you were before spraying chemicals into the unit. People often times make units worse by doing abstract things.
  3. burnt

    burnt New Member

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    sure i get where your coming from. i figured as much (and said as much too).
    just wanted to see if it would even make a difference or if the problem was elsewhere.
    just being open & thorough explaining my thought process
    this is more of a learning experiencing for me
    but thanks for assuming the worst of me :p

    i only sprayed a very very small amount
    directly in the middle of the gears where the axles connect

    i was very careful to wipe up any excess and not get on any belts
    or in the teeth of hte gears themselves or anywhere else.

    my next step was to get some proper lube // grease
    and do it all over again but now i know that it is worth doing.
    i figured that using the deoxit to flush // clean first
    and then lubing would be better than just lubing.

    ******
    anyway would like to get back on topic
    wondering where i should focus on for issues with the auto stop mechanism?
    having trouble identifying what is going on with how it even works.
    and why it might not be clicking over...?

    with teh FF, i can see the stop button press down a lil but not enough to click over.
    if i press the FF button again sometimes it will click over, sometimes it does not

    the PLAY does not do this at all.
    RW works everytime so far

    gunna do some more sleuthing but any insight is much appreciated
    thanks!
  4. SkywaveTDR

    SkywaveTDR Well-Known Member

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    On mechanical locking bar type transports there is a solenoid that would release the locking bard to cause stop to activate. This can be done through other means but if a solenoid is used then the sense system needs to be electronic. To figure this out Technicians will consult the service manual and if the auto stop in there is explained then you will know what is happening. It is unusual for one mode to work and another not as they are triggered from the same thing but I have seen where drive rubber or gears cause slight modulated movement of a reel table and this if optically sensed might cause the sensor to think that the reel is still moving when it is not but modulating- wiggling around. I use with the best results AMSoil Signature Synthetic oil for the bearings motors and anywhere else that needs oil. The grease is replaced after cleaned out with denatured alcohol with Lubriplate 105 grease that has not failed me in many years of service. I started at Teac in 1982 and even though I left got into Radio for 14 years then went back to tape deck repair, I have been doing deck repairs all the time. Even my work for Hughes on planes was with video tape decks. They don't use them anymore I am sure.
    The stop solenoid seems to be activated by a counter stop switch so this is not the issue. There has to be some lever that is not moving like it should to trigger the shut off of the flywheel assisted mechanism. It is a matter of study of what is moving and what should that will gain you the correction needed. I have not seen one of these for a while now as they don't come in. I do have a 424 Mk III I did fix recently here but it was again old grease.
  5. burnt

    burnt New Member

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    thanks so much for the insight.
    ah solenoid! thats what i thought it might be but didn't know what it was called.

    i keep running it back and looking at it trying to see how it works
    tbh it doesn't even look like the solenoid moves when the auto stop engages.
    everything goes so fast its hard to decipher whats going on.

    well i got some lubricant, grease and new belts on the way now
    gunna swap those and lube the gears // motor up and see where i'm at.

    unfortunately i just noticed that the main lil screw on the metal plate holding the flywheel
    was already stripped :(
    will have to figure out how to get it free or no bueno for me

    tbh if i can get this thing mostly working well enough to use i'd be a happy camper
    i got it for almost nothing as a untested for parts or repair kinda thing
    the price these things go for now even broken is redonk
    and was surprised it mostly works. thought it'd be all sorts of broke.
    worse case scenario its still a pretty nice lil mixer.
    love the VU's
  6. SkywaveTDR

    SkywaveTDR Well-Known Member

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    Well if that screw is stripped as the head is cammed out then a new one will be needed. I have a lot of metric screws here but some are a special length. Cammed out screws have been taken out using dikes or diagonal wire cutters to grab the head and turn it. Once it is out then you measure the diameter and then length and with that a new screw should be located- the threads are not often different as it is hard to make screws that size with all kinds of threads. Head screws for open reels are 2mm or M2. I don't recall ever measuring this as in my screw drawer at Teac and at my shop we have lots of screws and one of the type you need is probably in there. If you know which screw it is the service manual sometimes says the size. If not then they are just matched up but most small deck screws are M3 and there are some special ones like the 488 cassette compartment that are M2.6.
    Cammed out screw is from using the wrong drivers- we use JIS types here called Vessel that can be had at McMaster Carr. Even for Xcelite drivers I used those XST driver for many years without a problem.
  7. burnt

    burnt New Member

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    service manual says
    M2.6 x 14
    which i'm asumming is 14mm length

    of course i have lots of M2 and M3
    i think even some M2.5

    gunna wait til i have my other supplies before i investigate the problem screw more

    where do u usually apply the grease?
  8. SkywaveTDR

    SkywaveTDR Well-Known Member

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    I remove the old grease and apply Lubriplate 105 where that grease used to be. Bearings get oil. Slide plates as in head base need to be taken apart to get the old grease out and new in. Some grease I have seen is the same old Molytone graphite stuff that messed up VCR all those years.
    They seem to never learn.
  9. burnt

    burnt New Member

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    early days but so far so good
    replaced the tape counter belt
    the old one was looking loose
    & counter was sticking sometimes rolling over the hundreds

    i think the other belts are okay
    gunna hold on replacing them for now

    relubed the bearings.
    got that stripped screw loose with some flush cutters

    running way smoother.
    auto stop working for all 3 modes now too!

    exciting times :p

    will prolly take apart the transport & clean // regrease everything real good
    when i have some more free time

    thanks for all your help skywave

    ps do u have any knowledge on yamaha 4 tracks?
    have a MT120 that i can't get any sound in or out of
    no activity on the LED meter either
    Last edited: Aug 23, 2021
  10. SkywaveTDR

    SkywaveTDR Well-Known Member

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    Not much but a guy did bring in a unit Yamaha unit with a broken power jack and when I fixed that and restored power I tried to get audio out of that and it had nothing so I don't know. When they drop or throw these things around to damage the power jack as in rip it out then there can be plenty of other broken parts in there too.
  11. burnt

    burnt New Member

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    its really weird
    it powers up
    the tape transport part actually seems to work pretty smooth

    gleaning the service manual for clues
    i thought maybe the transistor mute circuitry might be the culprit
    as i've read those can be prone to failure
    but my readings w/ a multimeter seem to show they are working properly

    my next step is to trace the audio path and see where the audio drops out
    maybe i can suss it out to a central thing why all audio is not passing.

    i can't get any audio from the inputs, the tape, any of hte outputs, aux send // return
    i tried recording to tape then playing it back on a different device but no dice either.
    nothing at all.
  12. SkywaveTDR

    SkywaveTDR Well-Known Member

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    A failure that large has to be a power supply issue as all those section will not fail independently by themselves. Look for power to plug connection and make sure the solder joints are not cracked. Some Porta Studio use a regulator IC like a 7805 or 7812 that I have had go out but not more than 1 or 2. Start with the simple stuff- put in 1KHz sine wave and trace but I would be looking for lack of voltage as too many things are out.
  13. burnt

    burnt New Member

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    ah thats a good point
    ya it makes sense to me its gotta be like a central thing

    at first investigation last night
    all the different power rails seem to be working at proper voltage
    and seem to be getting to where they need to be

    didn't trace the whole entire unit but def the main areas, its going.
    can't see any noticeable cracks in the PCB either
    but i need to investigate more in depth
  14. SkywaveTDR

    SkywaveTDR Well-Known Member

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    Cracks in solder joints happen at connectors as they are moved by wires as people work on the units and the pin break as the solder is too little- that is why I use yards or Kester 44 .031" solder on decks all the time to correct many hundred solder joints that are substandard.
  15. burnt

    burnt New Member

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    i gotta stop being lazy
    and fully disassemble the boards and stuff from the case
    prolly will just reflow a bunch of joints and see if it comes back
    seems easier // less time consuming than tracing and guessing
    maybe getting false positives // negatives and getting not an accurate picture of whats what

    i checked all the connectors for continuity from one side to the other last night
    and they all checked out but i suppose that if the joints were shoddy
    that the multimeter might still say it was good :shrug:

    it wouldn't surprise me tho b/c when u unscrew the two halves of hte case and open it up
    the ribbon cables connecting both sides get super taut and pull on the connectors