Tascam 688

[bsco]

Got a quick question....Had a look on google and youtube but can't find anything useful...anyway, I have this deck that needed a drive belt.....So I replaced it.......The motor seems to be running at max speed....and the pitch control doesn't seem to do anything, but the deck is running so fast it is hard to tell if the pitch control is varying the speed....I have repaired cassette decks before and have had to adj the motor speed by adjusting the small speed adjustment inside the motor itself....This one has a small hole in the back of the motor and, without power applied, I can't find the small speed adjustment....So, I don't think the capstan motor in this unit has that feature.......so the motor might not be able to be adjusted like in a regular cassette deck.....has anybody here on the forum preformed motor speed adjustments on this unit?? any help would be great......
Cheers

[g1]

Yes I have, but it was so long ago I can't remember! I know some of the models had the speed adj. external on the board somewhere. Also, there is probably a regulator inside the motor which could be bad.
Before anything, verify that the capstan is contacting the pinch roller when in play. And it's a double speed machine isn't it?

[g1]

Service manual here:
TASCAM TEAC PROFESSIONAL DIVISION 688 MIDISTUDIO Service Manual free download, schematics, eeprom, repair info for electronics

[Enzo]

Agree^^^^

Get under the pinch roller and push it into the tape a little harder. it sounds like the pinch roller is not gripping the tape, and the takeup reel is controlling the speed. usually the takeup - which has a clutch - serves to maintain tension.

On any cassette deck, if your tape is running at five times the proper speed or some such, then the little speed tweak control in the motor is not the issue. if it is electronic, it is way more likely to be external to the motor.

[bsco]

Service manual here:
TASCAM TEAC PROFESSIONAL DIVISION 688 MIDISTUDIO Service Manual free download, schematics, eeprom, repair info for electronics

Thanks g1......there is a switch which selects the speed control source.....External, Fixed and Variable....There is also a pitch control as well......I will check out the pinch roller issue today.....I did clan it with some rubber renew.....it was dirty but not that bad.......and I don't think there is a speed adjustment inside the motor......

[bsco]

OK. Checked that out and when I excert extra pressure on the pinch roller, I can get the speed to slow down......however, when switched to variable speed mode, the control does not change the speed.......even with the extra pressure applied to the pinch roller......By the looks of it, I am going to need to replace the roller but before I do, I will need to get this pitch control working the way it should......if anything comes to mind, let me know.....The manual only has block diagrams there...I didn't see any schematics.....
Cheers,
Bernie

[bsco]

Agree^^^^

Get under the pinch roller and push it into the tape a little harder. it sounds like the pinch roller is not gripping the tape, and the takeup reel is controlling the speed. usually the takeup - which has a clutch - serves to maintain tension.

On any cassette deck, if your tape is running at five times the proper speed or some such, then the little speed tweak control in the motor is not the issue. if it is electronic, it is way more likely to be external to the motor.

Ok Enxo...I had a closer look at this after.....I managed to pop the rear cover off the motor to expose the electronic control board...There is a power transistor that is burnt...The solder joints are burnt.....all the parts on this small board are underneath....so I guess the motor is always running at full speed.....It is Mabuchi EG-530KD-2B......12VDC 1600/3200 RPM CCW.......I'll try another google search but if anybody knows where to get these motors let me know.....
Cheers

[g1]

We were just discussing that same motor:

http://music-electronics-forum.com/t40362/#post397057

http://music-electronics-forum.com/t40362/#post397202

[bsco]

We were just discussing that same motor:

http://music-electronics-forum.com/t40362/#post397057

http://music-electronics-forum.com/t40362/#post397202

Found it in Vancouver...Main Electronics...$15.75 Can......

[bsco]

Just for the hell of it, I got the board off the motor...C1470 transistor has overheated and burnt up the board....In order to get the board off you have to twist the two motor terminals 90 degrees...then the board slides up...also take note that there is a solder connection on the far left of this board (where the 4 wires are soldered).. that also has to be desoldered....as it is soldered to the metal case....

[bsco]

This one is for you g-1....I replaced that motor after and checked out the deck...It worked out fine.....customer is happy ....I am just getting a chance to post this now.....
Cheers.....

[g1]

Thanks Bernie. There was some question about possible counterfeit motors that could not be adjusted to speed without circuit modifications. At least we now know the ones from Main Electronics are legit.

[bsco]

Thanks Bernie. There was some question about possible counterfeit motors that could not be adjusted to speed without circuit modifications. At least we now know the ones from Main Electronics are legit.

Well......The motor that I put in works ok.......the problem this guy had was recording on a machine that was dragging..and of course, when he played it back it was fine.....until the motor gave out and started to run at top speed...so the tapes that he had recorded previously will not play properly anyway...no matter what......and the tape that he had supplied had something wrong with it.......it would stop erratically.....I tried a bunch of my tapes and they never stopped during play mode....for some reason, his tape would cause the machine to stop playing as if you hit the stop button.....The machine now plays great and the variable speed control works great....Gave it a good clean-up and that was it.....what mods are you referring to??? I wouldn't mind knowing about them in case I do run into the issue.....Do you have any info on this??

[g1]

No, it was someone that couldn't get speed right after motor replacement and thought it needed a mod to work. My opinion was there was some other problem with the circuit.
He bailed so we never found out.

[bsco]

No, it was someone that couldn't get speed right after motor replacement and thought it needed a mod to work. My opinion was there was some other problem with the circuit.
He bailed so we never found out.

Ok. Could be.....I guess we will never now......While we are here, I have to ask...did you ever run into a problem with the Yorkville NX series powered speakers such as the 55P and 750P where the circuit board would burn up underneath those 12K/5W resistors? I guess I should have started a new thread but.....I just thought I would ask.....
Cheers