644 repair

[keef]

Hi all,

This is my first post.

I have been given a 644 Portastudio which seems to be in great condition and I would like to get it all working. The mixer section works fine as far as I can tell. Only problem is with the cassette drive. Fast forward and rewind work fine - I am assuming these are separate motors. The only issue is with the play and record which do not work. If I hold back the two small pins in the corner of the cassette slot the motor runs fine but if I insert a cassette the motor will attempt to run but will then stop. I am assuming this is a problem with the capstan belt. I have ordered a replacement belt but I cannot find a guide anywhere to undo the unit to replace the belt. Anyone have a few pointers as to how to open up this machine?

Thanks

keef

 

[Laszlo]

Hey Keef,

there is a lot of basic DIY stuff on Youtube , it is worth to look. There is no video on belt change of the 644, but the 688 which is the big brother of it, with the same transport.

In case you are not familiar with this kind of activity, I would suggest to think everythig twice before you do it..These are fine little machines but they were quite complex and developed at the end of the cassette player era. Also mind that in case you damage the smallest piece, it would take a time travel to buy it in a regular shop It is not a bad idea to make photos before each phase too just to have it once get stuck in the reassemble phase. Good luck!
Laszlo

 

[keef]

Hi Laszlo,

Thanks for your reply and the video. It looks do-able to me if I can get the case open.
It looks like the 688 opens in a separate section for the recording section. Looking at the 644
I cannot see a join down the case at this point. Lots of screws underneath so maybe I will try this first. Good idea to take photographs.

If I don't mange to repair the cassette I wonder if it is possible to attach a minidisc or computer to record and just use the 644 as a mixer?

I have been reading the manual and it sounds like a very complicated machine.
Let you know how I get on.

Cheers,

keef

 

[Laszlo]

Hi Keef,
Since I dont have a 644 myself, I cant help too much in this. It would be vise to download the service manual from the net, and study the exploded views of the machine. That helps find out how to get inside. Dont start unscrew randomly screws on the buttom plate though, it might loosen something which is fixed to the bottom plate and once you unscrew it, it will be damn complicated undo it later.
Since you are new to this Forum (at least you said it was your first post) I would recommend you to wait a bit for other forumers, since I know there is a lot of knowledgable persons who breath and eat daily this stuff, and some also have knowledge specific to the 644.
On another note, you may use the machines mixer part solely, many do that. However, it would be a pity, since the really revolutionary thing in the Tascam home recording systems is the versatility and flexibility they built in, and these later machines offer really a lot.
cheers,
Laszlo

 

[keef]

Hi Laszlo,

Thanks again for your reply. I have searched for the service manual but without any luck.
I will keep trying. I have the operation manual. Reading this manual it does sound amazing what this machine can do.

P.S I have also been given a Roland drum machine which works great.

All best,

keef

 

[keef]

Hello all,

I have finally got a service manual and opened up the machine. I have rep[aced the belt. The old one was reduced to a small black sticky rubber deposit on the motor drive wheel. Obviously I cleaned this off before fitting the new belt. I have reassembled the machine.

Unfortunately there seems to be no improvement. Fast forward and Rewind both work fine and so does the shuttle button. I still cannot get the tape to play. If I remove the tape and hold back the two feeler switches in the top corner then the motor turns and the transport engages. The moment I put a tape in it stops.

If anyone has any ides as to what I could look at with this machine it would be appreciated.

keef

Tascam 644 with a new belt

 

[keef]

Hi,

To answer my own question.
The reason that play isn't working is that the capstan motor doesn't turn.
Seems that the motor is a Mabuchi EG-530KD-2b and these seem to be extremely rare.
May have to call it a day on this repair unless someone can suggest an alternative motor.

keef

 

[keef]

Update: I have installed a new capstan motor which I found on eBay. Installation wasn't too difficult. Follow the instructions in the video above to replace the belt and then it is a matter of easing off the retaining plate, removing the motor, 3 screws, cutting off 4 wires and resoldering and then replacing everything carefully.

All working fine.
keef

 

[Artinspace]

Hello and congratz on your 644. I recently got my own 644 ant try to solve same issue. Do you mind sharing service manual? Tried to open the machine but with no luck.

 

[Binarioman]

Hello all,

I have finally got a service manual and opened up the machine. I have rep[aced the belt. The old one was reduced to a small black sticky rubber deposit on the motor drive wheel. Obviously I cleaned this off before fitting the new belt. I have reassembled the machine.

Unfortunately there seems to be no improvement. Fast forward and Rewind both work fine and so does the shuttle button. I still cannot get the tape to play. If I remove the tape and hold back the two feeler switches in the top corner then the motor turns and the transport engages. The moment I put a tape in it stops.

If anyone has any ides as to what I could look at with this machine it would be appreciated.

keef

Tascam 644 with a new belt

Hi, how you opened your 644? I can´t do it. I´m stucked in the right side of the bottom plate.

 

[keef]

Hello,
Remove 9 screws from underneath then three screws from the back panel corner ( behind the cassette deck). Then remove knobs for the tape speed selector, tape speed mode selector and pitch control. Pull knobs upwards to remove. Then remove two screws from inside cassette loading tray. Then you can open the unit by lifting from the back edge. It hinges from along the front edge - with the wrist rest. Have a prop of around 30cm to place inside to keep it open. It will not open fully - about 25 degrees.

Hope this helps.

keef

 

[Binarioman]

Thank you Keef!
I´ll try again with your instructions.

 

[Binarioman]

Please Keef... What are the screws? The red ones? Or the blue ones?

 

[keef]

Hi, Its the two outside red ones at the top and one that is one not marked on your photo-
inside the hole in the corner bottom left. Cannot see in your picture if there is a screw in there. You may have taken this out already.

keef

 

[keef]

Going from left to right on the red row - numbers 1 and 4.

k

 

[Binarioman]

Thank you Keff! I did it.

 

[keef]

Great. Glad you did it.
keef

 

[-mjk-]

Please Keef... What are the screws? The red ones? Or the blue ones?

@Binarioman in general, screws that are immediately over/under/beside connectors, are screws that hold the connectors to the chassis. In reference to your photo, that would be all the blue screws, and the two center red screws, which you can see are all closely associated with connectors.

Sometimes, there are screws that don't seem to be associated with anything but are holding components on the inside that are screwed to the chassis. There's not too much you can do about that except put it back. But one thing I have learned is, if I take a screw out slowly and I see that it has a sheet metal thread, then chances are it's just holding the sheet metal cover on. If I back a screw out and it appears to have a machine thread, that means it's going into either a threaded standoff of some kind, or a nut. There is one exception to this rule and it is a screw with a plastic retaining thread. It looks almost like a sheet metal screw, but it'll have more of a blunt tip on it, and the threads will probably be more coarse than a sheet metal screw. Also, in my experience, these plastic retaining screws are all black oxide. Many of those connector assemblies are made of plastic, so there will be those plastic retaining screws holding them to the chassis. So if you start to remove one of those, and it doesn't look like a sheet metal screw, and it's near a connector, then most likely it's holding the connector assembly to the chassis.

Hope this helps!

 

[jita1]

Update: I have installed a new capstan motor which I found on eBay. Installation wasn't too difficult. Follow the instructions in the video above to replace the belt and then it is a matter of easing off the retaining plate, removing the motor, 3 screws, cutting off 4 wires and resoldering and then replacing everything carefully.

All working fine.
keef

Hello Keef. I know I'm a little late to the party here but my 644 also has the same problem where it won't play tapes. When I press the play button, it actually clicks like it wants to play and then it clicks again and nothing. FF, rewind, and shuttle all work fine, so just like yourself, probably won't need to replace the belt. I have old recordings that I want to transfer to Pro-Tools so I really want to get this thing working again. I contacted a shop who specializes in vintage recording equipment but they are 2 months behind because of Covid-19. I ordered the capstan motor (EG-530KD-2b) from eBay. You mentioned that you had to snip 4 wires. Can you elaborate on which wires they are? I might just wait and have the shop install the motor. Since I will have the part, they should only charge me for labor. On the other hand, my wife is an electrical engineer so I might have her help me LOL. Thanks so much to you and others here who showed me the way.

 

[keef]

Hi Jita1
Congratulations on your 644 and thanks for your comments.
The four wires I referred to are the ones connected directly to the capstan motor. I will try and attach a photo. I photographed the existing motor before cutting them off and then desoldered them in the same position to the new motor. A bit fiddly as they are so close together but it is possible with care. As you can see they are all colour coded. (You must make sure you get exactly the right motor as it is a two speed motor and as far as I know other motors will not work correctly without modification.)

The main thing when tackling this job is not to break anything else when opening the machine and getting to where the motor is attached. Just take it slowly and carefully . Take photos as you go.

Cheers,
keef