CT-F950 take up reel low torque in play

[Wardsweb]

The take up reel has great torque in FF. I can hold the take up reel and the motor will spin the belt. When I do the same in PLAY, it doesn't take much pressure at all to stop the motor and it will stay stopped when I let go of the take up reel. I checked the voltage to the motor and it is 5V in both FF and PLAY. Anyone see is before or have a clue what may be causing such an issue?

 

[tapetech]

Disconnect the reel motor wires and see if the drive voltage in play goes up. It should.

It is common for the reel motors to go south, so you may be running into this.

 

[pustelniakr]

5V is incorrect for that motor. During "Play," you should see somewhere near to 9v across the reel motor. The voltage should go up significantly during fast modes. A properly operating reel handling system should have the motor to continue to drive, and the clutches in the reels to slip if they are manually stopped. It is hard to see, unless you put marks on the different sections of the reel assemblies. You will have to remove the face plate, and then you can see the reel assemblies in action. While a cassette is being played, you should see one section of the take-up reel rotating faster than the section that is actually in contact with the cassette reel. You look through the cassette windows to see that (face plate has to be off).

Make sure that you are measuring the right points. If I remember correctly, the lines to the reel motor are red and blue. There is a terminal block on the top of the mechanism assembly where you can measure.

Is this a new machine for you, or have you had it for a while and it just started doing this? Has it been sitting for a while? Other info would be helpful.

If the motor has developed dead spots, and such (common at this age for these), if you are careful, you can rebuild it. Here a thread to help: http://www.audiokarma.org/forums/index.php?threads/ct-f1250-reel-motor-rebuild.53981/ Read the whole thing before you start.

Don't mess with the spring that holds the idler to the reel assemblies. The tire could be slipping and need repair. The clutches might need a bit of rework. There are other possibilities. But you gotta start somewhere. Pick the most likely candidate: the reel motor.

Enjoy,
Rich P

 

[Wardsweb]

5V is incorrect for that motor. During "Play," you should see somewhere near to 9v across the reel motor. The voltage should go up significantly during fast modes. A properly operating reel handling system should have the motor to continue to drive, and the clutches in the reels to slip if they are manually stopped. It is hard to see, unless you put marks on the different sections of the reel assemblies. You will have to remove the face plate, and then you can see the reel assemblies in action. While a cassette is being played, you should see one section of the take-up reel rotating faster than the section that is actually in contact with the cassette reel. You look through the cassette windows to see that (face plate has to be off).

Make sure that you are measuring the right points. If I remember correctly, the lines to the reel motor are red and blue. There is a terminal block on the top of the mechanism assembly where you can measure.

Is this a new machine for you, or have you had it for a while and it just started doing this? Has it been sitting for a while? Other info would be helpful.

If the motor has developed dead spots, and such (common at this age for these), if you are careful, you can rebuild it. Here a thread to help: http://www.audiokarma.org/forums/index.php?threads/ct-f1250-reel-motor-rebuild.53981/ Read the whole thing before you start.

Don't mess with the spring that holds the idler to the reel assemblies. The tire could be slipping and need repair. The clutches might need a bit of rework. There are other possibilities. But you gotta start somewhere. Pick the most likely candidate: the reel motor.

Enjoy,
Rich P

Thanks Rich - this is a deck that has been sitting here for at least 20 years. It was my father's. I just got an itch to bring it back online. I like your motor rebuild thread. I may try that next. I have already replaced all the belts and the idler wheel (NOS), as the rubber on the original was getting hard. I have worked on many of these over the years. I started my electronics life back in the 80's as an audio bench tech. Just haven't dealt with mechanicals in years. I've been doing more with tube amps and preamps, as of late. Thanks again for the insights.

Here is a picture of my work bench.

 

[pustelniakr]

I have seen some of the fruitof your labors. Some nice work.

The 950 transport is fairly elegantin its simplicity. I find that many idler tires out there are a bit too hard. If you can contact wjoe, his idelr tires for this application are a bit less hard, and bite better.

I don't remember the full voltage applied in fast modes, but the play mode voltage should be closer to to 9.0 than to 8.5v. Many reel motor belts are a bit thick and tight. Give it a bit of a stretch, or it will steal some of the motor torque, and make the motor work too hard while you are running in the rebuild. Mkae sure that you do not changethe foot print of the contacts on the armature. As is there should be good contact surface area. If you change the contact to armature contact, you will loose current carrying capacity until it runs back in. If you load the motor during this run in, you could make new burn spots at the slots.

Run your motor in for several hours, in play mode, before driving tape. Then watch the reel motor voltage when playing a tape. You will know when the rebuild takes, because the reel motor voltage will rise to over 8.5v and vary very little around where it rests. As the motor warms up, the voltage should go up a few tenths of a volt. That is good. REplace the transport micro-switches. They arel likely dirty DeOxit won't help without a wiping action. Just replace them.

Good luck,
Rich P

 

[Wardsweb]

Rebuilt the motor and now have 12v in FF/RW and 8.5v in PLAY. Still the torque in PLAY is lighter than I would like.

 

[pustelniakr]

Mark the edges of the 3 rotational sections of the take-up reel assembly. This is so that you can see the rotational differentials, as the reel is driven. I use Sharpies of differing colors.

With no tape in, put her into play. You really want to run her like this for a day or two. In any case, momentarily stop the tape-up reel, and see if the idler continues to drive its drive surface on the reel assy. That part of the reel table should continue to rotate, even though the reel is stopped. I don't remember if it is the middle or the bottom section of the reel assembly. See where you are losing torque: motor stops, belt slips, idler drive pulley slips, idler tire slipping, or play clutch (in the reel assembly) too loose.

Take-up torque is going to be significantly less than torque in fast mode. You just want to spool up the tape fed to it from the pinch roller. You don't want to "pull" on the tape, or you can get wow and flutter or mis-tracking issues.

Also, verify that the reel idler continues to drive its section of the reel assembly in fast mode, if you manually stop the reel. In fast mode, you will have to hold the tape presence sensor button in, since the head block does not rise to do it for you.

Enjoy,
Rich P

 

[pustelniakr]

Progress?

Enjoy,
Rich P