Author Topic: TASCAM 688 portastudio play back too fast  (Read 395 times)

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Offline G

TASCAM 688 portastudio play back too fast
« on: May 18, 2017, 02:36:55 PM »
I posted this over on homerecording.com and got some good advice and direction on replacing the capstan servo assembly or recapping the servo board.

However, I stumbled on this thread here: http://www.vguitarforums.com/smf/index.php?topic=16460.0

-- and saw that one of my favourite posters on here Elantric has the 688 also, and there was some good advice on the 238 which I've seen has the similar capstan motor issue. 

Since I'm more of a VG-99 guy than an analog recording guy, I figured you guys could give me some advice on what I should do next, bearing in mind that I am a complete amateur with no soldering experience. 


Here is the post I made over there and subsequent updates I made as I learned more:





Hi all,



I'm having a problem with tape speed being too fast from my Tascam 688 portastudio.

In this video, the first part shows the music how it's supposed to sound (From my digital workstation), and the second part shows how it sounds from the tape. It's about 2x faster.

You can see me fiddling around with the pitch control to show the difference, and I kept the tape door open so you can see how the heads are working.  When I recorded the track, I did not manipulate the pitch control or speed in any way.

I tried other recorded tapes as well, and all had the same speed problem (about 2x fast).  They are all Maxell XLII tapes.

As a background to what lead up to this:  When I first recorded this track (last summer), all was fine with the speed.  Now, after a long winter of disuse, I decided I wanted to start using the portastudio again and noticed this speed issue.

As a background on the machine itself, I purchased it last summer from a very good seller who took care of it immaculately, it was barely used and in like new condition, still had the box and all.  It's worked perfectly up till now.

I've read on some forums that it might be a circuit issue, or a capstan issue, but I would truly appreciate some specific insight from anyone on this case, and what I should do to fix it!

I admit I am relatively new to this, so I'd really hope its just some dumb oversight on my part!  (I am willing to take more videos or photos to show anyone to get a better idea of what is going on.)


UPDATED X1:

I know this probably means nothing, since I'm just compensating for the new faulty speed, but I just recorded a few different songs to tape, and they're playing at the speed I recorded at. So I guess if nothing else, the speed failure is consistent?

UPDATED x2:

1. i'm looking at this place near where i live that claims to be an authorized service center for tascam to get it repaired: AUDIOTECHNIK -- does it look any good? any questions i should ask to gauge their experience?

2. can drastic temperature change be the cause of this capstan servo assembly failure? just recently it went from frigid cold and snow to 100 degrees Fahrenheit and extreme humidity over a few day period. could that mess up the pitch speed circuits/motor? or is it just general aging?

3. does this issue have serious long term repercussions if left alone? since i can still record with it now, i'm weighing the option of just using it as it is with the faulty speed. i'm not nearly experienced enough to make any qualified decisions, so unless i get some help with this i feel like i might do more damage than good!


Sincerely,
GAC

« Last Edit: May 18, 2017, 02:39:31 PM by G »

Offline Elantric

Re: TASCAM 688 portastudio play back too fast
« Reply #1 on: May 18, 2017, 03:01:22 PM »
Quote
I tried other recorded tapes as well, and all had the same speed problem (about 2x fast).  They are all Maxell XLII tapes.

You do understand that the Tascam 8 track cassette PortaStudios (1985-1993) were designed to run Metal Tape running at 3 1/2 inch per second (IPS) = twice the typical speed of standard cassettes ( 1 7/8 IPS)   

and the 688 is NOT designed to work with pre-recorded standard cassettes

But Cassette tapes recorded on the Tascam 688 should playback at the same speed ( pitch) as the audio fed into its input jack
« Last Edit: May 18, 2017, 03:32:18 PM by Elantric »

Offline G

Re: TASCAM 688 portastudio play back too fast
« Reply #2 on: May 18, 2017, 03:10:05 PM »
Hi Elantric! 

Yes, I do understsand that much -- I recorded what you hear on the video with Maxell type II tapes on the same device (the 688) I'm playing it back on.

The new recordings I just made after noticing the speed issue are playing back at the same speed as I recorded them at -- its the type II tapes I recorded last summer on the 688 that are playing too fast.

Offline Elantric

Re: TASCAM 688 portastudio play back too fast
« Reply #3 on: May 18, 2017, 03:28:51 PM »
Quote
ts the type II tapes I recorded last summer on the 688 that are playing too fast.

I have No answer for that one ( unless it was recorded on a different model - that has a switchable capstan speed control switch,



or a Tascam MIDI-izer syncronizer



( or Tascam ATS-500) was employed and not calibrated, or if Tascam 688 "Sync" switch was accidentally set to "External" - the 688 capstan will run at the wrong speed during record or playback . 




or if the Tascam 688's rotary "Pitch" control knob was not "centered" during recording / playback

elektrotanya has the tascam 688 service manual
https://elektrotanya.com/tascam_teac_professional_division_688_midistudio.pdf/download.html

older thread is here
http://www.vguitarforums.com/smf/index.php?topic=16460.msg118441#msg118441

other resources
http://www.phys.tue.nl/people/etimmerman/recordingfaq/multi/tascam.html

http://music-electronics-forum.com/t40323/
« Last Edit: May 18, 2017, 03:57:11 PM by Elantric »

Offline Elantric

Re: TASCAM 688 portastudio play back too fast
« Reply #4 on: May 18, 2017, 03:51:12 PM »
another possible cause of the 688 wrong record / playback speed is a rubber capstan pinch roller that has aged.

i know the rubber capstan pinch roller's on my gently used 1992 Tascam 688 are now rock hard and wore out and need replacement - just from sitting idle for 25 years

Offline G

Re: TASCAM 688 portastudio play back too fast
« Reply #5 on: May 18, 2017, 04:00:53 PM »
Quote
I have No answer for that one ( unless it was recorded on a different model - that has a switchable capstan speed control switch, or a Tascam MIDI-izer syncronizer ( or Tascam ATS-500) was employed and not calibrated

Everything I've recorded has been on the 688.  All tapes I have are recorded and played back on the 688.  I have no other cassette deck or cassette recording devices, or any other types of tapes -- only the 688 and type II tapes.

Quote
elektrotanya has the tascam 688 service manual

i only seem to be able to find a german version of the manual on elektrotanya, but the seller did provide me with a (poorly) photocopied english version  :-X

Quote
or if the Tascam 688's rotary "Pitch" control knob was not "centered" during recording / playback

this is possible, i was still messing around when i first started out and might have overlooked that, so i just did a test using a tempo checker.

while the pitch control is all the way to the left (the slowest speed), its still about 5 bpm faster than its supposed to be (in the digital version of my recording).

at the exact center, it's about 25 bpm faster than the original digital version of my recording.




as far as i know, i've always kept it at dead center, but i wont put it past me to have made an error like that.  the tempo discrepancy still confuses me though.

i'm not sure if there is any relevance in that, but i wanted to make a note of it....





« Last Edit: May 18, 2017, 04:09:20 PM by G »

Offline G

Re: TASCAM 688 portastudio play back too fast
« Reply #6 on: May 18, 2017, 04:07:59 PM »
Quote
or a Tascam MIDI-izer syncronizer

( or Tascam ATS-500) was employed and not calibrated,

i have neither of these...


Quote
or if Tascam 688 "Sync" switch was accidentally set to "External" - the 688 capstan will run at the wrong speed during record or playback .

that's possible, but even in my amateurish state, I would have noticed the tape speed being on EXT because the yellow light blinks.  i may be slow, but not that slow!


Quote
other resources
http://www.phys.tue.nl/people/etimmerman/recordingfaq/multi/tascam.html

http://music-electronics-forum.com/t40323/

Thank you for these links!  I will look through them extensively

Quote
another possible cause of the 688 wrong record / playback speed is a rubber capstan pinch roller that has aged.

How can I check if this is the problem?

« Last Edit: May 18, 2017, 04:18:09 PM by G »

Offline G

Re: TASCAM 688 portastudio play back too fast
« Reply #7 on: May 18, 2017, 04:21:13 PM »
Quote
http://music-electronics-forum.com/t40323/

I tried like the guy in this thread did to slow down the pinch roller by applying pressure with a q-tip -- it did slow down, but returned to the same faulty speed after letting go.

Offline Elantric

Re: TASCAM 688 portastudio play back too fast
« Reply #8 on: May 18, 2017, 04:42:54 PM »
Then it could be a dry electrolytic capacitor on the internal PLL speed control voltage regulation power supply (typical problem with older electronic gear)

Quote
another possible cause of the 688 wrong record / playback speed is a rubber capstan pinch roller that has aged.

Quote
How can I check if this is the problem?

lift the cassette bay door and inspect and touch the rubber capstan pinch roller  - if it feels like hard metal and not like rubber,   then ozone has destroyed its effective pinch roller function on the capstan for maintaining correct speed, as the take up reel motor winds the tape too fast.   

http://homerecording.com/bbs/user-forums-by-brand/tascam-user-forum/midistudio-688-problems-282166/
Quote
Many electronic parts places carry belts. Not sure about your area. If you can get the old ones out in one piece, they can measure them and get you replacements. Sometimes they come out looking like bubble gum if they're really bad. If you go this route, keep in mind that they are probably stretched out a little so get them slightly smaller than what they measure. If you can't find them locally, just call Tascam or a Tascam service center and get the belt kit for your unit. As far as cleaning, use head cleaner or isopropyl alcohol on the heads and capstans. Use rubber cleaner/rejuvinator (again found at electronics stores) on pinch roller/belts. That's another thing to check also. Make sure your pinch roller(s) are not shiny and hard. They should look and feel like rubber. If they more resemble plastic, you should replace them if they can't be cleaned/rejuvinated with rubber cleaner. Normally, degaussing is not as big of a deal as cleaning, but if you find it necessary, you should be able to get a degaussing wand at an electronics store also. They are getting tougher to find since the cassette has kind of gone by the wayside. Hope all this helps and good luck!


http://ronsrepairs.com/project-profile-the-tascam-midistudio-688-multi-track-recorder/

« Last Edit: May 18, 2017, 06:30:10 PM by Elantric »

Offline G

Re: TASCAM 688 portastudio play back too fast
« Reply #9 on: May 21, 2017, 02:32:58 PM »
Quote
Make sure your pinch roller(s) are not shiny and hard. They should look and feel like rubber. If they more resemble plastic, you should replace them if they can't be cleaned/rejuvinated with rubber cleaner

Quote
if it feels like hard metal and not like rubber,   then ozone has destroyed its effective pinch roller function on the capstan for maintaining correct speed, as the take up reel motor winds the tape too fast.

it definitely feels hard like plastic, a little shiny. there isnt any rubbery give to it.  i took a picture of it, how does it look? maybe you cant tell much from a photo but here it is attached:




Offline Elantric

Re: TASCAM 688 portastudio play back too fast
« Reply #10 on: May 21, 2017, 02:40:25 PM »
If it's hard as a rock yes you'll have to track down a brand-new rubber pinch roller good luck

Offline G

Re: TASCAM 688 portastudio play back too fast
« Reply #11 on: May 21, 2017, 02:44:34 PM »
As an additional note, the original recordings seem to have slowed down  -- not back to normal, but instead of 25 bpm faster than usual, 18 bpm.

I tested the BPM of all the tracks the day I noticed this problem, all of them were 25 bpm faster than the original digitally recorded track.

Now, they're all 18 bpm faster.

I will note that I havent done anything yet, havent tried cleaning the pinch roller or anything.

The only thing that's changed is the temperature once again has dropped significantly to much cooler after a temporary heat wave...

Offline Elantric

Re: TASCAM 688 portastudio play back too fast
« Reply #12 on: May 21, 2017, 02:48:10 PM »
It's concerning that you haven't done anything yet as that reveals you have not read the owners manual and which states you must maintain the capstan and the head cleaning maintenance procedure at least once a month when using that machine it's a critical aspect of the tracks on such a limited space and head gap


Offline G

Re: TASCAM 688 portastudio play back too fast
« Reply #13 on: May 21, 2017, 03:00:45 PM »
i only used this machine once after i bought it for about 5 songs during a recording session last summer.

severe health issues and frequent hospital trips took priority for a while after that.

now that i'm feeling slightly better again, i'm up for the task.


does this look like the kind of thing i should be getting?



http://www.ebay.ca/itm/REEL-TO-REEL-PINCH-ROLLER-BELT-CLEANER-REJUVENATOR-/131346334412?hash=item1e94da02cc:m:mLJv-KXRPaoLQHoevygw-_g


Offline Elantric

Re: TASCAM 688 portastudio play back too fast
« Reply #14 on: May 21, 2017, 03:06:04 PM »
Yes start with that

Hopefully ( with luck ) the rubber pinch roller will restore its essential griping properties

Offline snhirsch

Re: TASCAM 688 portastudio play back too fast
« Reply #15 on: May 22, 2017, 05:29:13 AM »
it definitely feels hard like plastic, a little shiny. there isnt any rubbery give to it.  i took a picture of it, how does it look? maybe you cant tell much from a photo but here it is attached:
(Image removed from quote.)

The pinch roller appears to have a glaze on it.  Torque from the takeup reel can increase speed if the tape is not being held firmly against the capstan. 

Offline ffata

Re: TASCAM 688 portastudio play back too fast
« Reply #16 on: May 22, 2017, 08:07:41 AM »



[/quote]


Mmmmm... 8-Tracks!  :D

Offline G

Re: TASCAM 688 portastudio play back too fast
« Reply #17 on: May 23, 2017, 02:00:06 PM »
Quote
Yes start with that

Hopefully ( with luck ) the rubber pinch roller will restore its essential griping properties

Thank you Elantric, I will let you know how it goes.  Once the rubber cleaner arrives in the mail, I will clean it right away.

Quote
The pinch roller appears to have a glaze on it.  Torque from the takeup reel can increase speed if the tape is not being held firmly against the capstan.

Is there a specific technique to cleaning the pinch roller, or is it straightforward just applying and wiping with a gauze?

Offline admsustainiac

Re: TASCAM 688 portastudio play back too fast
« Reply #18 on: May 23, 2017, 02:26:17 PM »
Quote
Is there a specific technique to cleaning the pinch roller, or is it straightforward just applying and wiping with a gauze?