Tascam 688 idler tire, lube and other help requested

Discussion in 'TASCAM DIY Repairs and Mods' started by SpringGoose, Nov 13, 2019.

  1. SpringGoose

    SpringGoose New Member

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    Like many people, I'm trying to restore my Tascam 688 so that I can transfer my old recordings to digital. Mine plays slow and very likely varies in speed while playing. The motor and capstan belt were replaced (by somebody else) but didn't seem to fix it. I have a PDF of the service manual, and I am going to attempt to:

    1. Change the idler tires and belt (just to be sure), sourced here:
    https://www.dynamtechgroup.com/tape-reel-belts.php

    But I can't find instructions on how to do the idler tires. No video or posts that I've located.

    This video shows how to do the belt:


    So that probably gets me most of the way. Advice appreciated for the idler tires.

    2. Restore the pinch roller (as they are not currently available). Sounds like lightly sanding it and then washing it with soap and water is my best bet.

    3. Lube and oil as @SkywaveTDR has preached using Lubriplate 105 and AMSOIL Signature Series 0W-30 motor oil. I still need some pics on the exact locations to lube and oil though as I don't want to mess that up.

    4. Change the battery while I'm in there. It's a CR2430 for those wondering.

    Lastly, the person at dynamtechgroup.com indicated that most likely the speed issue is not the motor but "it is a board component problem (capacitor) that is easy to fix" and he is going to follow up with instructions. When I get this info I'll post it here for others to benefit from and hopefully be able to do that repair myself.

    Advice on idler tire replacement, pinch roller restore, and lube locations for the Tascam 688 welcome. Thank you!
  2. Faraz Hussain

    Faraz Hussain New Member

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    Any luck with your restoration? I have a 688 and it too is suffering from random slow playback. Hopefully it is just belt. But if I open it up, I'd rather have everything to fix it at once.
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  3. telengard

    telengard New Member

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    Wondering the same thing, I'm having issues w/ my unit and any info on best practices for maintenance while I"m in there (lube/oil locations, etc) would be suer useful.
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  4. SkywaveTDR

    SkywaveTDR Well-Known Member

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    I have one here but the client wants it returned so he can use it so I am compelled to send it back to him. The motor may have been changed by a person that has no clue- many people out there are like that. They think they know but they clearly do not demonstrate that from all the units I have seen. What motor did they put into the deck? Being a Pitch control is used I think the requirement is a 4 terminal type motor. Keep in mind that these are double speed decks for Chrome tape only. They then run at 3.75IPS and must be calibrated with the MCT111 tape. I am a past Teac Technician so I do not do sloppy work and I have had to modify some Porta studio speed control circuits to use a different motor- if you are good it can be done.

    These decks often use the same transport as others. In that the part can be taken apart the same way. It is not always simple and may require taking parts off that you do not want to- I have to do it too not just you. I will look at the video and see what I can see of the transport type.
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  5. SkywaveTDR

    SkywaveTDR Well-Known Member

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    OK, After recovering from sea sickness of the video, the transport looks to me like the 238 type transport again but with no direct drive motor. That may mean it is more like a 488. In any case to get to the reel motor and idlers you place a screw driver in between reel table where the screws are recessed and take them out and that causes the reel drive system to drop out the back. Keep track of these screws as I dropped one once and found they were M2.5 X16mm length which are not all that common. They have them at Mc Master Carr but they sell them by the 100. It is then simple to replace the square seal on the idler and then put it all back together- I oil the top bearing of the reel motor with AMS and make sure the rotation is easy. I had one deck had shrunk plastic causing the shaft to bind. I think the seal is one that they don't have at Mc Master and so I obtained a bunch from ACE Seal in Californy. The square seal last longer and work well when cleaned off with alcohol to remove and mold release that might still be on there. Use of a magnetic driver would be of help as the screw is recessed and not easy to get in. Let me know if you have more questions- this is all information that can be had by looking at the parts layout of how the transport goes together.
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  6. SkywaveTDR

    SkywaveTDR Well-Known Member

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    For the guy making a video to instruct others the right terms should be used for the parts- Lifters are used in open reels not cassette decks and the lever arm go to Pin switches that are located on a board behind the mechanism gear motor. These need to be sprayed directly into not AT. This required me to take the transport assembly apart. The Flywheel which you call something else is taken out and oil in the bearing is AMSOil not Teflon grease. The thrust plate can get Lithium or Teflon but the important part is the oil in the bearing. Also know that when putting the flywheel back in the capstan shaft MUST be cleaned of oil before you play a tape as the shaft will have oil from going through the bearing. Denatured usually removed that oil but don't get alcohol into the bearing as it should not get into the bearing. Pinch rollers usually do not have to be replaced and there is way too much replacement going on which is a large waste of time. Pinch roller are meant to be cleaned even though no one does it. How do I know? I see them horribly dirty all the time. I do not use Lithium grease and I have used Lubriplate 105 for many years. It is safe for plastics as I would know by now if it was not.
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  7. SpringGoose

    SpringGoose New Member

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    @SkywaveTDR thank you so much for such detailed responses. I did not receive an email notification that you'd replied even though I should have. I'm going to reach out to you via a private message about having you do the work on my Tascam 688. Thank you again.
  8. wkrbee

    wkrbee Active Member

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    That video is the typical "ham handed/ a little knowledge is dangerous" YT video. The guy that said "it's the caps-it's a easy fix" has never been inside a 688 .
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  9. SkywaveTDR

    SkywaveTDR Well-Known Member

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    I have not had a cap cause speed problems in many years other than the Pioneer RT909 I worked on but the guy ripped up all the foils so the cap wasn't in the circuit anyway.
    It is more a problem of lubrication or a broken solder joint or even possibly a dirty cal or pitch pot. The 122 Mk III type transport that is in the 488 Mk II has the reel motor come out the same way with two small special screws from the front as in under the cassette holder. In Porta Studios they may not have a cassette holder so the two screws which mount the motor are recessed about 1/2 inch. I say they are special screw because I have had to order them and they are a unique length as well. M2.6 X 5mm
    I looked at the 688 transport and it seems the reel motor is mounted on a reel motor plate behind the main plate- examination will indicate what needs to come off.It looks like the same small idler tire as the 122 Mk III. The screws in this unit are M2.6 X 17mm length and they go through a white plastic mounting piece. That is not your speed problem. I oil the capstan motor top bearing and the cam and reel motor bearings as well as Capstan Bearing. I have seen wow and flutter at high speed below .03%.
    Of course you only need to know the screw size if you drop and lose one and it even happens to me.

    The Pinch Roller which is too new to need replacing, can maybe be found at the DIY website that Marion operates out of Slovakia. I have gotten two size of roller from him and they were all good and reasonable price. https://fixyouraudio.com/
    Go to shop and Pinch Roller by size- you will need a caliper to determine width, Diameter and bearing size. MPJA.com has them in carbon for about $9.00- the caliper that is.
    Last edited: Jun 11, 2021
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  10. SpringGoose

    SpringGoose New Member

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    @SkywaveTDR thanks again for taking the time. I have an update to clarify some information from my initial post. But first...

    I also found this video showing a fairly comprehensive Tascam 688 disassembly. His unit had a broken belt but he doesn't actually show the belt replacement procedure:


    I also found a newer video (only about 7 months old) of another Tascam 688 disassembly. In this one he refers to the the "pitch control pcb" and "pitch board" which I thought was interesting seeing as how my main issue is speed related:


    Now, referring back to my original post. I mentioned that someone told me the playback speed issue was cap related not motor related. I looked back and he was referring to the known issue on Tascam 238's called a runaway motor, which I assume means the motor would run at full speed. This obviously isn't the issue I'm having.

    I still have not started my repairs. and would love for you @SkywaveTDR to do the work. I'm going to reach out again.
  11. SkywaveTDR

    SkywaveTDR Well-Known Member

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    The 238 is a direct drive SMD cap problem and I have fixed about 132 of those motors. It has nothing to do with a 688 which is a cheaper motor and a belt drive system. You can not apply the same answer found in one motor to a totally different kind. Like Jim says, he has never been in a unit. Next time I get a 688 here I will see what it takes to get to the reel motor drive but these should not be getting worn out yet as they were the newer product. They sure are complicated though.
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  12. SpringGoose

    SpringGoose New Member

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    I believe the person was simply mixed up, I don't think they actually thought the 238 was the same transport as the 688.
  13. SkywaveTDR

    SkywaveTDR Well-Known Member

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    There are a lot of people who are mixed up. That is why I avoid YT videos as these people are also mixed up- the only thing that can be said for them is that they know someone that can take a video. Some of them look as if they are on the ocean and some do a lot of unnecessary panning. Some you would think you were watching Batman. I watched one tube video where the guy was taking things off you do not have to- this is done on the X1000R all the time by amateurs and like the X1000RBL I got from SC the guy broke a lot of parts, bent things and made his work even more concrete as a bonehead as he only put half the screws in.
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