Midistudio 688 problems

[andrej]]

hi! i got this machine not long ago... it's great and i'm really into it, but, it has a not-so-slight problem: it stops all the time! when i press play, it plays for a couple of seconds and stops. i press play again and the same thing happens. after several repeats (an pressing the transport buttons is annoying, because the buttons are somewhat old and hard to press), then it plays okay for some time. this happens especially when the tape is near the beginning or the end. the same goes for rewind, forward and record. it resets the counter when it stops, just like it does when it reaches the beginning while rewinding, this might be a clue about what's happening, possibly a transport problem. the battery is certainly not the problem, as i changed it and memory works.

now, tips for you about the battery.
the machine is complicated, i opened it up. you need to be extra careful. you can't remove the battery from it's holder, nor can you find a suitable battery. it's 3v, lithium (not lithium-ion! it's not rechargeable) big and kinda spot-welded to it's holder. so, i removed it and it's holder by desoldering it and replaced it with a battery holder from a computer motherboard (cmos maintenance). the pin distance is suitable, you just need to bend one pin a LITTLE. the original one has 3 pins, while the computer one has 2, so you have to connect 2 of the pin terminals together on the copper side of the pcb. with a wire a normal cmos maintenance battery (found in most pc-s) is also lithium, 3v and suits the machine perfectly. it's also commonly available, cheap, and easily changeable because of the new socket you installed (though you'll only change it once a decade), so it's perfect. don't forget to backup your scenes to cassette before changing the battery, as disconnecting it will erase them.

i tried to help, so, can anyone help me?

[MONTE]

Haven't worked on one of those for a while, but if memory serves, theres a take up reel sensor that works off the tape counter. This is to keep the machine from eating tape. In other words, if the take up reel isn't working, or if the machine THINKS it isn't working--STOP. Most of the time it's just the belt going from the mechanism to the tape counter. You might want to change any/all belts if you're going to get into the machine. I would "pop the hood" and make sure there are no broken or sloppy/worn belts. Good Luck!

[andrej]]

that helped a lot! i'll try and see this weekend, since it's a bi*ch to disassemble.

i've never replaced belts. are they standard, or i need to find tascam ones? how to find 'em and the degausser, cleaning packs, etc?

[MONTE]

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!

[Masterherm]

Originally Posted by andrej]

hi! i got this machine not long ago... it's great and i'm really into it, but, it has a not-so-slight problem: it stops all the time! when i press play, it plays for a couple of seconds and stops. i press play again and the same thing happens. after several repeats (an pressing the transport buttons is annoying, because the buttons are somewhat old and hard to press), then it plays okay for some time. this happens especially when the tape is near the beginning or the end. the same goes for rewind, forward and record. it resets the counter when it stops, just like it does when it reaches the beginning while rewinding, this might be a clue about what's happening, possibly a transport problem. the battery is certainly not the problem, as i changed it and memory works.

now, tips for you about the battery.
the machine is complicated, i opened it up. you need to be extra careful. you can't remove the battery from it's holder, nor can you find a suitable battery. it's 3v, lithium (not lithium-ion! it's not rechargeable) big and kinda spot-welded to it's holder. so, i removed it and it's holder by desoldering it and replaced it with a battery holder from a computer motherboard (cmos maintenance). the pin distance is suitable, you just need to bend one pin a LITTLE. the original one has 3 pins, while the computer one has 2, so you have to connect 2 of the pin terminals together on the copper side of the pcb. with a wire a normal cmos maintenance battery (found in most pc-s) is also lithium, 3v and suits the machine perfectly. it's also commonly available, cheap, and easily changeable because of the new socket you installed (though you'll only change it once a decade), so it's perfect. don't forget to backup your scenes to cassette before changing the battery, as disconnecting it will erase them.

i tried to help, so, can anyone help me?

As a Troubleshooter and audio repair technician who probably worked about a hundreds of those tascam 688 series,every time you open one of those units and make an attempt to fix it with out any success,you compromise the unit to a point that no technician will be able to repair it and give you a reasonable service fee.Belts are measured with special belt measuring tools,the unit is tested not by the consumer users manual but by using the units service information,its a very thick book by the way.frequencies have to be calibrated with signal generators and a scope and so forth.If you carefully look at the bottom of the unit it says "refer to qualified technician only".
Save the unit,save some money,Ship it to a qualified service technician.No other way around it.

[andrej]]

hmm, got it to work. i taped a piece of folded paper onto the edge of the cassette - over the erasure window (it still had that tab for recording), and now that problem shows up rarely.

as for fixing it, i live in montenegro, and, i believe that the nearest tascam service center is in germany. it's at least 20 kilos in weight, so - shipping it to them and back and paying for the fix would probably be more expensive than the unit itself, or even a new digital 8-track...

you said you used to fix them, did you work for tascam? there are service and repair companies for audio stuff around here (serbia, montenegro, etc.), but i doubt they know anything about this machine more than i do. it's really not a common tape recorder, or even a common cassette multitrack. are there any other companies that fix them?

you said you had a service manual for it, do you still have it? can i get it from anywhere? i have considerable electronics knowledge, enough to follow it, (and i have access to some pro equipment and know how to use it). the belt size is probably written in the service manual, right?

i try to have a professional approach, and when i don't have the layout, i take pics while disassembling it.

and what if the only problem is the small belt to the counter? i also need to change the transport microswithches. what do you think, how much would that cost, including shipping? i'm a high school student, i don't make money often, and i don't make a lot...

[Bobby Darko]

would love to see those pics andrei. keep us posted. I have 2 688's as well and I will have to change the belts and battery sooner or later! good job on finding the manual.

[bobbybluz]

I've got a manual, the supplemantal scene guide and the original scene tape.