yet another 688 speed issue thread

[heatmiser]

hey,

I've been reading threads on 688's for years on here (including moog's current one) and am feeling pretty overwhelmed.

I've had a second hand 688 for about 4 years now and I absolutely love the thing for so many reasons, but am getting so frustrated by the varying speed of the transport. I bought it at a local regional chain and already had them send it back for "transport issues" under warranty a few years ago and it worked fine for a few months. The last couple of years have seen a gradual decline in reliability.

It used to be that the pitch would vary from one project to the next. Now it has progressed to the point where during one take, the speed will suddenly and dramatically change. Pretty much unusable in its current state. So frustrating in fact that I actually placed a losing bid on a roland vs 2000 today eek close call with digital there...but I'm just so sick of tape speed issues.

Is it even reasonable to consider packing it up and shipping it off to tascam in california? I might be able to bring it back to the store in portland maine where I bought as they have an "authorized tascam service center" in new hampshire and might be willing to look at it, although their prior repairs didn't last.

You guys on this forum are so tech oriented I find it amazing. I just don't have that bent...I once replaced a worn out belt on a fostex x-15 with my daughter's elastic hair tie and it worked great for months afterward. That is how lame I am when it comes to repairs.

Are severe pitch issues likely motor related, or possibly just rubber belts/rollers? The pinch roller is cleaned with a wet q-tip regularly and I consistantly get gray/black film from it. It has a shiny-ish strip on the surface about the same width as the tape.

One odd thing I noticed tonight is that the metal pin that the pinch roller presses against is spinning constantly when powered up...not normal is it? None of my other decks do that.

Sorry for the long post and for the vague questions...just looking for any general encouragement and/or guidance...

Thanks,
Peter

 

[Beck]

Sometimes factory authorized service can be the wrong thing. They normally replace parts in chunks, possibly in this case with the same type PCB that failed in the first place. So you get another few years out of it and then the same components (likely capacitors in many cases) fail on the “New” part. Those that replace individual capacitors with something completely different than the factory parts may see more of a permanent fix (Though nothing is eternal in the world of electronics).

The rubber pinch roller will eventually go bad on most decks and will need replacement. The symptoms of sticky or slippery pinch rollers are more jerky and wobbly speed fluctuations. Rubber belts need to be replaced now and then as well. The pin you see spinning is the capstan and they will spin if a cassette is inserted… depending on machine. It did in all of my portastudios, but I didn’t have a 688.

It never hurts to replace pinch roller, capstan belt and control belt if they haven't been replaced in the last few years. Even if something else is wrong it will be difficult to track down if things are slipping or sticking due to bad rubber.

 

[heatmiser]

Thanks Beck!

So, maybe I spring for belts and roller (from what I've seen online they are quite inexpensive) and try to do those things myself. There are some old threads about that...maybe I try to get the service manual. Then, if I'm lucky - problem solved...otherwise, at least I can rule those things out.

Do you have to have the part numbers yourself when you call tascam, or can I just describe what I need and order (probably backorder ) over the phone?

Taking this thing apart looked pretty intimidating in one thread I dug up a few weeks ago...I'll search for it again soon.

Oh, and the capstan (I've heard that term a million times but didn't know that's what it was until now ) spins whenever the unti is powered up regardless of whether there is a tape in there or not. Seems like a poor design to have some motor running constantly whether or not it is needed, doesn't it?

 

[sweetbeats]

You don't need the part numbers before you call Tascam.

AFAIK the speed issues that plague 238's are the same as that which plague the 688, and it is a motor control issue...not the motor itself, but a chip that goes bad on the servo board or something...do a search on "238 speed" or something.

Wouldn't hurt to call Teac in California...the "analog support" department. You'll likely get Jimmy and he'll give you the low-down on what you might need to do, and what it might cost were you to ship it to them. They'll do the job right if they can.

Wouldn't hurt to get new rubber but I'd be surprised if that resolved the issue. Sorry to be a downer...

It is pretty common for the capstan to spin whenever the unit is powered up...this was the case with my Tascam 48 and 58 decks, my 424mkII as well as my big ol' Ampex MM-1000. My Tascam BR-20T capstan spins up when the right tension arm is raised. This is the case with my 388 as well and any of my Ampex 440's. So some are one way, some are the other.

Give Teac a call...at least you might know more about where you stand.

Good luck.

 

[heatmiser]

You don't need the part numbers before you call Tascam.

AFAIK the speed issues that plague 238's are the same as that which plague the 688, and it is a motor control issue...not the motor itself, but a chip that goes bad on the servo board or something...do a search on "238 speed" or something.

Wouldn't hurt to call Teac in California...the "analog support" department. You'll likely get Jimmy and he'll give you the low-down on what you might need to do, and what it might cost were you to ship it to them. They'll do the job right if they can.

Wouldn't hurt to get new rubber but I'd be surprised if that resolved the issue. Sorry to be a downer...

It is pretty common for the capstan to spin whenever the unit is powered up...this was the case with my Tascam 48 and 58 decks, my 424mkII as well as my big ol' Ampex MM-1000. My Tascam BR-20T capstan spins up when the right tension arm is raised. This is the case with my 388 as well and any of my Ampex 440's. So some are one way, some are the other.

Give Teac a call...at least you might know more about where you stand.

Good luck.

Thanks much for the advice sweet.

Ok, I'll get over the spinning capstan thing. Just seemed wasteful to me, but sounds like it is extremely common. My other decks didn't do it, but they weren't great decks, so...

I guess I better give teac/tascam a call. I really love this machine and miss it already. Played around with it last night tracking crazy effects-laden guitar stuff where pitch didn't matter as much, but not usuable for any kind of normal music at this point. Bummer.

I guess I may try replacing some stuff on my own still, or I may just send it in, or...I might still just (gasp) give up. I've been eyeing others on ebay, but starting over with an unknown quantity could be just as bad if not worse.

At least this will make a decent board even if the the tape portion is useless. We shall see. Thanks again for your thoughts.

 

[A Reel Person]

Hey

Your 688 recordings rock, so don't give up.

AFAIK, the capstan will spin at all times when the unit is powered up.

AFAIK, the 688 is belt driven, so replacing the capstan belt would be the first thing I'd do in your case. A loose belt can cause any number of speed fluctuation issues.

I know the repair of these monsters can be intimidating. More of a pain the the Aye for more experienced techies, but still a pretty good teardown of the unit.

I'm sure there's at least one detailed post on 688 belt replacement. Search it up, and don't give up til you find it.

Good luck and hang in there.

 

[heatmiser]

Your 688 recordings rock, so don't give up.

AFAIK, the capstan will spin at all times when the unit is powered up.

AFAIK, the 688 is belt driven, so replacing the capstan belt would be the first thing I'd do in your case. A loose belt can cause any number of speed fluctuation issues.

I know the repair of these monsters can be intimidating. More of a pain the the Aye for more experienced techies, but still a pretty good teardown of the unit.

I'm sure there's at least one detailed post on 688 belt replacement. Search it up, and don't give up til you find it.

Good luck and hang in there.

Thanks Dave. That is very nice of you to say . I don't get the kind of raw clarity that you do with casette, but I have my own thing going which I kind of like and am glad you do too.

So, I just got off the phone with tascam service in calif.

Talked to several dudes...mostly very nice, but not very optimistic. They did not seem very interested in trying to fix it. First guy says send it in and if we can't repair it, we'll return it to you for free. When I mention it weighs close to 40lbs. he back tracks and offers to dispose of it for me for free.

I told him I really was interested, but would prefer to talk to someone about the possibilty of it being repaired before I invested in the shipping (I'm guessing about $80?) and $45.00 fee for an estimate. He transferred me to the service manager (didn't catch the name - bad connection).

This dude was really nice as well, but he also talked a lot about how much it would cost to ship to them and how they might not have any parts and how I'd have to pay to ship it back to me. He asked what the problem was, I told him, and he immediately diagnosed it as a failing capstan motor. He recommended I speak with parts to see if the motor was even available.

I got transferred to parts. I asked about the availability of a capstan motor, any belts and the pinch roller. He checked and said the capstan motor has been discontinued, the pinch roller is not available and may or may not be able to be back ordered (?) but they did have what he said was the only belt for this unit, the capstan belt @ $9.80.

So, I don't think I will be sending it to them. Again, all very nice guys. Obviously I don't expect them to be able to diagnose it over the phone, and I could send it to them only to find that the problem is something else entirely that they could repair, but they seemed very doubtful so I will not take the risk.

I guess now I will check one last time for any possible local repair, maybe order the capstan belt on the off chance that replacing this will solve the problem, or I will simply use this as a mixing board only and seek out another recorder of some kind.

Sorry again for the long post - just thought some might be interested. I long for the days of my youth when we had this grumpy old vietnam vet down the street who fixed just about any electronic device for next to nothing out of his garage. His whole place was jam packed with tubes, wires, circuit boards, etc. Where are those dudes these days ?

 

[sweetbeats]

heat...get the belt and try it out. Maybe its the fix.

So sorry the call to Teac wasn't much of a gain if any.

But Dave is right. That belt could be the problem or a problem and $9.80 is pretty cheap in my book for ruling something out that likely needs replaced anyway.

Interested to see if anybody else has comments on what the folks at Teac had to say.

Don't give up.

If you had the service manual I'd recommend you look up the procedure to test pinch roller pressure too.

Does the issue seem to be related to changes in the tape you are using?

Can you take any pics of your pinch roller?

 

[heatmiser]

heat...get the belt and try it out. Maybe its the fix.

So sorry the call to Teac wasn't much of a gain if any.

But Dave is right. That belt could be the problem or a problem and $9.80 is pretty cheap in my book for ruling something out that likely needs replaced anyway.

Interested to see if anybody else has comments on what the folks at Teac had to say.

Don't give up.

If you had the service manual I'd recommend you look up the procedure to test pinch roller pressure too.

Does the issue seem to be related to changes in the tape you are using?

Can you take any pics of your pinch roller?

Thanks sweetbeats. Yes, of course you're right. I should at least try the belt. Not a big deal to at least try. I know there is an old detailed thread on the process. I will call them back tomorrow and order it.

Don't be sorry about the call. They were very nice and I got a good dose of reality. It helped by way of ruling something out (shipping to them), although it wasn't what I wanted to hear.

I do not have the service manual (do have the owner's manual though), but have thought about buying one online ($40?).

I have always used Maxell XLII C90s and C60s and had great luck previously. The pitch problems occur with brand new tapes after limited use. Those same type of tapes used to perform fine in this machine.

Yes, I should be able to take photos, although it is somewhat tight in that tape compartment, I'll see if I can capture any clear images and share them...

 

[cjacek]

First off, I'd highly recommend you get a capstan belt which, I believe, is the reason for the pitch changes. It costs $10 + ship and a cheap way to confirm the issue. It's fairly typical of slow decline in speed stability, over the years, when the belt gradually stretches out and rides on the outer metal spool / ring thingie attached to the motor. Again, an inexpensive way to trouble shoot is change the belt.

Actually, have you tried opening the 688 and checking the belt? How loose is it or is it firmly riding where it should be and is not slack? If the previous service people knew what they were doing, maybe they already replaced it? So, before you order, CHECK the belt AND, if you can, post some close up clear photos of the belt for us to see, from several angles.

Also, and I'm not sure how close the 688 is to the 244 / 246 portastudio when it comes to the transport but it'd be good to verify which other rubber components it has. Can you see 2 idler tires and control belt? Again, when you open it, it'd be cool to check that too. Tho the first most important, for now, is the capstan belt so report back on it. Me thinks that it's a simple issue of the belt.

 

[heatmiser]

pics, pics & more pics

Ok, not much of a photographer here...sorry...so hard to get close up and stay in focus.

First, just because I had the camera out...the set up:



Now, the 688 (not necessary, but for those who haven't seen one maybe interesting):



Now, down to business...the roller and the heads:



Now, a close up of the capstan roller - note the glossy-ish strip in the center I mentioned earlier. The white flecks are photogrpahic artifacts I believe. Although there is some dust, It didn't look anything like that in person!

 

[heatmiser]

one more...

One more pic...really unrelated, but again, since I had the camera out...my '68 SG special and '65 Ampeg Reverberocket:



Maybe of interest to some...sorry - couldn't resist !

 

[cjacek]

Check the belt, my good man. You need to open it up. Capstan roller looks fine but could use a bit of careful application of caig rbr.

 

[heatmiser]

First off, I'd highly recommend you get a capstan belt which, I believe, is the reason for the pitch changes. It costs $10 + ship and a cheap way to confirm the issue. It's fairly typical of slow decline in speed stability, over the years, when the belt gradually stretches out and rides on the outer metal spool / ring thingie attached to the motor. Again, an inexpensive way to trouble shoot is change the belt.

Actually, have you tried opening the 688 and checking the belt? How loose is it or is it firmly riding where it should be and is not slack? If the previous service people knew what they were doing, maybe they already replaced it? So, before you order, CHECK the belt AND, if you can, post some close up clear photos of the belt for us to see, from several angles.

Also, and I'm not sure how close the 688 is to the 244 / 246 portastudio when it comes to the transport but it'd be good to verify which other rubber components it has. Can you see 2 idler tires and control belt? Again, when you open it, it'd be cool to check that too. Tho the first most important, for now, is the capstan belt so report back on it. Me thinks that it's a simple issue of the belt.

Thanks man. Yes, I will order the belt tomorrow regardless. The cost is incredibly small. I would have been willing to pay a fair amount of money to have this repaired correctly, so $10 is nothing. I should've bought it on the spot, but my mind was reeling at the time from the other bad news.

I have never opened this thing up and wasn't going to since I planned to have it worked on professionally by tascam. I didn't want to mess anything up. Now that I have decided against sending it back there, I am more willing to open it up and (carefully) take a look around. I will check the belt and take & post photos. Is the quality of the pix above acceptable/useful? I had a hard time and had to hold a flashlight at various angles while focusing.

Thanks so much for all of the input so far guys!

 

[cjacek]

Yes, those are very good photos. The word indeed is "careful" when opening it up. I hope someone here can chime in that has actually opened a 688, to make it less of a trial & error.

I think you're doing the proper thing. I would not let anyone screw around with my portastudio and when you have to consider shipping.. forget about it. Take your time and you'll be fine with some assistance from the guys here.

BTW, that's some serious hardware, in your 688, from what I can see. Oh my, am I seeing things or is this a 3 head deck?

 

[heatmiser]

Yes, those are very good photos. The word indeed is "careful" when opening it up. I hope someone here can chime in that has actually opened a 688, to make it less of a trial & error.

I think you're doing the proper thing. I would not let anyone screw around with my portastudio and when you have to consider shipping.. forget about it. Take your time and you'll be fine with some assistance from the guys here.

BTW, that's some serious hardware, in your 688, from what I can see. Oh my, am I seeing things or is this a 3 head deck?

Thanks. There is an older, detailed thread on opening it up, but it is all text and no photos as I recall. I will find it again soon and refer to it.

I don't know about the head count, but it is a serious piece of engineering from the looks of it (did I mention it is 38lbs !). According to the manual it has:

Head Configuration:
8 channel record/play (sendust) x 1
8 channel rease (ferrite) x 1

So, I guess that means just two?

 

[sweetbeats]

heat...

You go, man.

Great pics. Love seeing pics of other's setups. Your SG and Ampeg combo are sick. I had a chance to borrow a vintage Ampeg B50 valve bass combo once. It sounded incredible. That SG is a keeper huh???

Also, never enough pics of 688's. I'm glad you took the time to put them up.

Here...this is a thread with some detail about opening up a 424mkII. It will most certainly have loads of differences from opening your 688 up but there might be some applicable generalities: https://homerecording.com/bbs/showthread.php?t=289340

This is maybe a first, but I have to differ from cjacek on the condition of your pinch roller. It looks hardened. Some of the rubber compounds get gooey...some just get hard and glazed. Then some others harden and get these little bumps on them. They'll work, but it is a recipe for increased flutter. The original pinch roller on my 58 looked like that. If I were you, I'd get a new one. Now, Tascam said they didn't have them?? That stinks. I was able to get a new one for 234 and that is quite a bit older. Can you get the part number for it from them or did they give it to you? I could cross-reference. If you need to, send it to Terry (Terry's Rubber Rollers). You will get a better than new roller. You may pay a bit more than a new part from Teac, but if they are NLA then that isn't really an issue. Terry is a gauranteed service. I whole-heartedly support him.

Daniel et al, there are indeed only two heads, but on all the 8-track Teac cassette decks (238, 488, 688) it is a staggered head to increase the crosstalk performance.

 

[cjacek]

I don't know about the head count, but it is a serious piece of engineering from the looks of it (did I mention it is 38lbs !). According to the manual it has:

Head Configuration:
8 channel record/play (sendust) x 1
8 channel rease (ferrite) x 1

So, I guess that means just two?

Here...this is a thread with some detail about opening up a 424mkII. It will most certainly have loads of differences from opening your 688 up but there might be some applicable generalities: https://homerecording.com/bbs/showthread.php?t=289340

This is maybe a first, but I have to differ from cjacek on the condition of your pinch roller. It looks hardened. Some of the rubber compounds get gooey...some just get hard and glazed. Then some others harden and get these little bumps on them. They'll work, but it is a recipe for increased flutter.

Daniel et al, there are indeed only two heads, but on all the 8-track Teac cassette decks (238, 488, 688) it is a staggered head to increase the crosstalk performance.

Ah, yes, good explanation on the heads. Yeah, my JVC cassette deck has those "staggered" type heads but they're 2 separate ones so that's why I wondered.. Still, that 688, as are many of TEAC machines, is a marvel of engineering and quality honest-to-goodness components. It's worth getting it up and running, for sure.

Cory, I'm completely on board with you on the pinch roller but my comments mostly related to the context of the speed issue. I actually misspoke somewhat. I didn't want to unnecessarily alarm heatmiser on needing to replace that roller but rather focus first on the capstan issue, which should be the first order of business.

See, if it is something else, like the motor or something which regulates speed, that's gone south, then I think investing a little capital on the capstan belt (which I believe is the real major problem) would make sense first, to at least confirm that it is the capstan belt that's the issue. Then and only then, IMHO, should the focus be on restoring / replacing the pinch roller, idlers etc...

I just did not believe the roller to be an immediate issue to contend with BUT I wholeheartedly agree with you on your points about replacing / restoring that roller but we differ slightly on the "when".

As long as we're inserting links (and an excellent one from Cory), lemme post my own:
https://homerecording.com/bbs/showthread.php?t=297394

Obviously not a 688 but a bit of commonalities here.

Again, thanks Cory for the explanation on the staggered head design.

 

[A Reel Person]

Belt and pulley

I'd check and change the belt, for sure. While in there, I'd also make sure the pulley is properly affixed and tightened to the capstan motor shaft. A little slippage can cause a lot of grief.

 

[sweetbeats]

Cory, I'm completely on board with you on the pinch roller but my comments mostly related to the context of the speed issue. I actually misspoke somewhat. I didn't want to unnecessarily alarm heatmiser on needing to replace that roller but rather focus first on the capstan issue, which should be the first order of business.

See, if it is something else, like the motor or something which regulates speed, that's gone south, then I think investing a little capital on the capstan belt (which I believe is the real major problem) would make sense first, to at least confirm that it is the capstan belt that's the issue. Then and only then, IMHO, should the focus be on restoring / replacing the pinch roller, idlers etc...

I just did not believe the roller to be an immediate issue to contend with BUT I wholeheartedly agree with you on your points about replacing / restoring that roller but we differ slightly on the "when".

Well put...I understand now. I agree 100% with cjacek.

Shame on me for jumping a little too quickly to a conclusion about what you were saying.

It's worth getting it up and running, for sure.

Yeah, heat. I'm sure you are gathering that we all think you ought to open it up and have a look at things and get that belt coming from Teac. At the very least you'll know the machine better and feel closer to it, and you may very well address your issue or at least you'll know more about what the issue is or is not and then can make some decisions based on that new info.

Just go slow, take pictures (both for being able to reassemble easier but also, selfishly, to see some pics of 688 guts up here...that would actually be great for other 688 owners if you have the time...totally understand if that doesn't work out tho'...), and when something isn't coming easy post up what's happening and I'm sure we can figure it out.