Tascam 688 play back too fast

G

gac

Member
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.)

Sincerely,
GAC
 
are you saying you recorded at 1 7/8 and it sounds like 3 3/4, or, you recorded at 3 3/4 and sounds like 7 1/2 ips ?
 
I dont see those speed options as available on this portastudio?

All I know is I recorded on this tape speed setting, and with the pitch control at 12 o clock, and playback at the same setting is now way too fast:
3584871396704056592-account_id=3.jpg
 
688 is fixed speed at 3 3/4ips.

The 122 mkII/mkIII, 238 and 688 experience a common failure with the capstan servo assembly, the result of which is the capstan running too fast. You need to purchase a new capstan motor (which includes a new servo board), or try the repair that is pretty well documented on the internet (try a google search "Tascam 238 capstan repair") which involves the PITA process of recapping the servo board.
 
Thanks sweetbeats!

Is something like recapping the servo board doable for an amateur like me? I'm still barely wrapping my head around the stuff on the outside of the machine, let alone inside it!

Alternatively, I looked for capstan motors on ebay, is there a specific model I should look for? This is all very new to me.

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?
 
Yes that's one of the websites I've seen that details the repair.

It's not easy. I don't know what your experience level is, but they are all surface-mount caps...a real PITA. I did the repair to my 238 capstan servo board and it was unsuccessful. I have a decent amount of soldering experience. I ended up getting a new assembly from Tascam in Montebello, CA. You'd have to contact them to see if they have any stock. I recommend calling as opposed to emailing.

Just to be sure, when you turn on your 688 does it sound a bit like a jet engine winding up? Like, does it *sound* like the motor is spinning too fast?
 
hey sweetbeats,

there has always been a slight hum coming from the back right area of the unit while its on since i first got it, but it's barely noticeable. is that normal?

i have never soldered anything before, so needless to say, my experience level is nil. ive been playing my own music for 15+ years, but i always had more tech savvy friends to deal with these issues for me.

some questions:

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: Reparation Pro Audio Repair – audiotechnik.ca -- 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!

once again thank you for your time sweetbeats, i've been up all night frustrated and drained soaking in all the information, it's a lot to wrap the mind around!

i will look at your thread now!

GAC
 
The hum is normal. I hear it on mine as well.

Before you do anything, have you checked the capstan belt? If that is loose then the motor won't move consistently. Temp changes affect rubber belts and will make a problem like your describing happen. Sometimes a belt will still look and feel good, but will be slipping and not pulling the capstan flywheel evenly and speed issues like this are the result.

I have heard of the problems with 238 and was always under the impression that the known problems with it had something to do with the direct drive capstan that it has which the 688 doesn't. In any case, you'll want to get to the belt and inspect it but I'd go ahead and put a new one in just to rule it out. It's not the easiest job but there's a thread here (and some other places I think) which will help.
 
My bad I didn't realize the 688 wasn't direct-drive. But I still believe it uses the same capstan motor and servo assembly...can anybody verify?

As to the OP's other questions:

1. I don't know...but the fact they are an authorized service center is a plus (typically). I would pay them a visit to discuss the issue, get a feel for their shop, etc. If it seems like they don't know what they are talking about or aren't familiar with the 688...or it just feels fly-by-night I might look elsewhere. But otherwise ask for an estimate or if they charge a nominal flat rate to evaluate the problem and go from there.

2. I suppose it could. Can't say for sure. If electrolytic caps were close to failure then just about anything can send them over the edge. Certainly the unit can handle the environments you describe, and what is important is to help make the transitions gradual. If I'm bringing something in from a damp freezing shop or storage unit I like to have it in a box and keep the box closed so things acclimate more gradually.

3. Well this is totally your call. There's no saying the speed is constant now that it is operating differently. If you can hear test tone tracked to tape varying in frequency I wouldn't continue to use it...your recordings will be unusable. And keep in mind any projects you do on your 688 as-is will not be playable on any other 238/688...the faster tape speed will also effect more wear and tear on your tape path, though you'd have to operate it out-of-spec for a *long* time to really see the effects of that...those things aside if the speed is stable, you aren't planning on playing back your projects on another machine you certainly could keep using it as-is.

Just to be sure...before this problem arose, you'd get about 15 minutes of record time off of a C60 cassette, yes?
 
hey sweetbeats,

thanks for your input again!

i will go check out the service center and tell them about the problem and get a feel before lugging this giant piece of hardware in.

canadian winters are so extreme, one day its a blizzard, next day its a blistering hot summer, and then it settles into spring!

i'll try the test tone, is there a length you'd suggest for an adequate frequency test?

these are the tapes i'm using, i have a giant crate of them, but thus far i havent actually filled an entire one up, i've been using one tape per song:
Maxell-XLII-S-90-US-1988-89-fr.jpg

i've been asking around in some other forums, one of them suggested that if the rubber pinch roller hardened, then it could cause slippage and thus too fast a speed, does that sound like it might be the case at all here? i took a picture of the roller itself, one member said if its shiny and plastic like rather than rubbery, it might need to be replaced:
7577041887108657220-account_id=3.jpg
 
Here was the post I was recommended:

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.
Click to expand...

Midistudio 688 problems
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!
Click to expand...
 
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...
 
On decks where you can remove the door (or, play with the door open), you can apply drag on the supply spindle to judge how good the idler wheel is. It has to perform better than the 7/16" capstan and 2" idler. ahaha
 
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