tascam 688 - disassembly and (hopefully) repair)

  • Thread starter Thread starter heatmiser
  • Start date Start date
The heads on the deck can be adjusted that allows correct contact alignment on the printed tape but once again, you need the correction alignment tapes and other equipment to get it done correctly...these tapes are almost impossible to source. It needs servicing by a professional. If you want to do it yourself thats ok too...just be prepared for failures as well as the successes. Sorry I cant help with the manual but if you research this site (and others) its very possible it has been uploaded before somewhere.
 
These machines have analog part - mixer, pots, eqs etc., and digital part - routing (think 24 x 14 mixer). I've opened only right side - meaning digital board. Haven't checked the analog boards yet (only headphones are dead there), but it mostly works.
As switching is done via lcd and 1-10 buttons, I assume its some sort of logic failure (like dead 74hc chip). I'll check of I can get to analog board, but checking servce manual might save some labor there
 
Last edited:
I just checked back here, also glad to see this thread is still going. It really helped me pull apart and repair my 688. I also got the name of the motor and a location that sells them, in case the capstan motor gives out. It was Main Electronics in Canada. I bought two brand new motors about $19 apiece.

A tip I discovered is not to use too long a tape. I bought some 20 min cassettes(about 5 min rec. time w. the 688) and they worked fine. But when I used a 90 min cassette tape, I kept having problems w. slight flutter. So I bought some 30 min. cassettes (which is about 7.5 min w. the 688) and they work fine. I find them for sale on ebay. Anyway, with new belts, cleaned and service captstan motor and pulley, it is working great(it sat in my closet from 2002 until about 6 months ago.) And I owe it to this thread for having the photos, etc. Thanks Heatmizer.
 
oh, also, I bought a compartment to be able to replace a battery easily, and soldered it in, and put in a new battery.
 
Hello there again! I'm very excited to tell you that i've repaired 688 to ALMOST mint condition! (We'll, minus broken 1-4 dbx switches and dead headphones)
I've opened analog part, and long circuit board under the channels - motherboard which connects to modules-channels. Basically, i've removed the motherboard and sprayed 4th channels connectors as well as motherboard 4th strip - worked. Probably those japanese 74hc chips will not die in my lifetime. I must say, the beast is well designed. I've enjoyed modding and pulling apart 414 - what a beautifully simple design! But 688 is a whole another story. Its a monster. But a well designed one.

Just for some clarity: how tracks transfer between 4 and 8 tracks? My 4 tracks tapes have track 1-4 sounding, and sometimes (parts of 1-4) 5-8, but with slight delay. Is it backward compatible with 4 track?
 
Another update. Tape must be mixed down to 4 tracks only to be compatible with usual 4 track, or tracks 5-8 suffer from slight delay
 
Hi guys,

Very happy to read this forum.

I'm trying to repair my 688 with a broken belt and burnt motor. I found a belt on eBay and a motor, but the motor is a EG-500KD-2B. It has the same characteristics. The seller told me it is compatible on 688.

Everything's running fine, but when I record, the recording is slow and fluctuate up and down sometimes. I can't use it.
Is there something on the deck for adjusting the speed? I don't know if it's a motor problem, or a setting on the PCB.

Sorry for my english, I'm french.
 
Soundcity said:
Hi guys,

Very happy to read this forum.

I'm trying to repair my 688 with a broken belt and burnt motor. I found a belt on eBay and a motor, but the motor is a EG-500KD-2B. It has the same characteristics. The seller told me it is compatible on 688.

Everything's running fine, but when I record, the recording is slow and fluctuate up and down sometimes. I can't use it.
Is there something on the deck for adjusting the speed? I don't know if it's a motor problem, or a setting on the PCB.

Sorry for my english, I'm french.
Click to expand...

Welcome to the forum.....I didn't buy my motor on ebay..I bought it from a company out of Vancouver.....it was the exact replacement...did you use the pulley from the original motor?? Is it possible that the pulley or the belt is slipping?? It wouldn't take much....I had to re-read your post...you also bought the belt from ebay....Does the unit play your pre-recorded tapes ok??
 
Bsco has hit it on the head, from your description I would be looking at the belt...but also just in case you're are not used to using cassettes, sometimes the spool becomes tight. A thing to try is fast forward the tape till the end, turn it over and fast forward it again. this practise allows the spooling on the tape to reset/tension itself again. Another thing to do is to pull out the cassette and physically twist it in your hands (be careful not to beak it) but if you hear a small "click" it is the wheels sitting back into their guiding grooves, it sometimes does the trick. Or simply use a new cassette of course.
 
Thank you guys.
The belt doesn't seem to be loose but I'll try the forward technique. Also I use the original pulley.
I'll post some audio example of recordings so you can hear what kind of problem I have.
I never use this machine before, I bought it 50 bucks.
 
Soundcity said:
Thank you guys.
The belt doesn't seem to be loose but I'll try the forward technique. Also I use the original pulley.
I'll post some audio example of recordings so you can hear what kind of problem I have.
I never use this machine before, I bought it 50 bucks.
Click to expand...

Put in a pre -recorded tape and switch it to regular stereo or 2 track mode....and see if it plays back ok.....I think there is a switch selector for tape speeds next to the speed control.....make sure that is not bad...and do check that speed control as that could also be a problem....I only had one of these units to repair for a friend of mine some time ago...his problem was the motor and belt.....that has been my only experience with these units to date...and I would not put too much faith in buying parts from ebay....also a previous poster suggested F.F. the tape and then rewind it...that should always be done even with brand new tapes....it just settles the tape on the spools and balances out any areas where the tape might be wound on the spools too tight in the assembly process......and make sure you use a good quality tape...I ran into problems similiar to yours with cheap tapes in other multi track recorders.....Hope this helps..
Cheers

P.S. I like your user name...soundcity....I have a 4X12 cabinet that I use with my 76 Marshall and 74 Les Paul....Sounds wicked....and I also have the 150W Sound city bass head as well....which I plan to rebuild one of these days.....
 
I forgot to mention...did you clean the heads?? If you only paid $50 for the unit I would guess that it will need some cleaning as well....
 
I cleaned everything in the console: faders, EQ, Mic Pre, Dolby PCB, every PCB cards, tape deck (pulley, heads, rubber, etc...)
I just tried to forward the tape (4 times).

I'm not a specialist, but I feel like it's a BIAS problem or something like this

Here is a popular track I record on 2 tracks, so you can judge the problem by yourselves.
Have a listen, it's very strange.

Thanks again for your help, I'm so desperate :)
 
Last edited:
Something's definitely amiss with the transport, probably the capstan or pinch roller. If it were me, I'd try replacing the capstan belt first.
 
I just changed the belt, it seems to be ok with it, and I don't have old recording for comparing.
Because I'm newbie with cassette deck machine, I don't know how should be the pinch roller sensibility. At this stage, I think I'll also try to change it, if I find one.

There's no way to modify the tape speed? It seems that the pitch knob doesn't react.
 
Soundcity said:
I just changed the belt, it seems to be ok with it, and I don't have old recording for comparing.
Because I'm newbie with cassette deck machine, I don't know how should be the pinch roller sensibility. At this stage, I think I'll also try to change it, if I find one.

There's no way to modify the tape speed? It seems that the pitch knob doesn't react.
Click to expand...

The pitch knob should change the motor speed. However, given how much the speed is changing already I'd be surprised if you could hear the difference.
Usually this kind of effect comes down to one of three things:
1. The drive belt is slipping ==> new belt
2. The tape is slipping ==> adjust or replace pinch roller
3. The motor controller has gone weird

If the capstan motor really did burn up, that might be an indicator that something is iffy with the controller. That's not something I have a lot of experience with, especially not in cassette decks.
It's possible that something is obstructing the motor or capstan somehow, or it might be a problem with the feedback from the motor since it appears to be servo-controlled. I can't find the service manual online so beyond that it's guesswork, I'm afraid.
 
Ok.... Do you have a pre-recorded tape....one that was done in a factory...could be a tape of country, rock, anything...see if it plays back ok....
 
You must log in or register to reply here.
Back
Top