AMI I gripper motor work or...not

[cedric]

Hello to all.
I have a problem with my AMI I (in restoration)
95% of the time,  at the end of a disc, side B only (I specify side B only) nothing happens (so, only 5% of the time, no prob, everything is ok)
The cutoff can be heard, but nothing happens. The tone arm stays on the disc.
If I try to turn manually (by the window) the gripper motor, I can feel resistance, it's energized, it's like being stuck.
So, I turn off the service switch, then I feel gripper motor become free, so I can turn manually 1/2 turn gripper motor, turn on the service switch, and then it's ok, gripper motor work normally.

What can energized gripper motor like this? Not enough to make it turn but enough to block it. Especcialy at a time when gripper motor should not be energized 
Contacts are ok, they open and close correctly with the switch actuator camshaft.

I don't have a problem with the B-side selection, no problem to start listening. It's only at the end of the disc, nothing happens. Thank you all.

[jukenorman]

Hi Cedric,
My gut feel is that it's a problem with the stopping switch (B side). The stopping switch is returned to its "normal" position when the selection pin is reset. When the stopping switch resets, it applies dynamic braking to the transfer motor. If the pin doesn't either fully reset or the stopping switch operates slowly, then the transfer motor doesn't immediately stop and jams.

Norman.

[cedric]

Hi Normand,
Thanks. Selected pin is always well repositionned. So, it can be the stopping switch who is slow ?
When you say "slow", you want to say incorrectly set or something else ?
Thanks a lot and have a good evening. Cedric.

[Hildegard]

Hi Cedric,

Sometimes with micro switches a "click" can be heard, but still they do not open or close correctly. Means they can work fine often but fail every then and now. The problem can be dirt inside the switch. So just hearing a "click" is not enough to be sure a micro switch works fine.

Hildegard

[jukenorman]

Hi Cedric,
Had you replaced the stopping switches or are they still original?

Norman.

[cedric]

Hello Hildegard, Normand,

Thanks. They looks new (probably change by previous owner, I don't know) There's "CE" label on them, and they looks clean.

I'll check thme this morning, and post pictures. Thanks

[cedric]

Hello,
So I've check the 2 stopping switch. Effectively, they're recent. I've test minimum 50 times each. Open, close with beeper or ohmmeter.
They work.
I continued to search, with manual near me. I've clean and try to adjust the rear and front cam switch.
And then,the prob has shifted. Before, it was at the end of the disc that gripper motor would not start.
Now, it's the opposite, it's when gripper motor must begin to work (gripper is on the magasine, but gripper motor doesn't start) Side A and B.
Just a little help (less than 1/2 turn with my finger by window), and it goes.
So, I've take some pictures of rear and front cam switch. I know that's not easy to have an idea by pix, but maybe you see something wrong?








Thanks

[jukenorman]

Hi Cedric,
When the record is returned, a contact of the cam switch opens (8/9), drops out the reversing relay and a closing contact of the reversing relay then dynamically brakes the transfer motor.

You can manually drive the transfer motor towards the end of its travel and observe the cam switches operating.

Maybe the contact of the reversing relay requires cleaning? If the dynamic braking is not effective, the transfer motor will tend to over drive and jam. In other words, when the cam switch operates, the transfer motor should stop dead.


Norman.

[cedric]

Thanks Normand, reversing relay is clean but I think the prob is not far from him.
I continue and let you know.
Have a good evening.

[cedric]

Hello everyone,
I'm still searching, but I can't find it. Sometimes it works, but sometimes it doesn't. I have disassembled the motor gripper but left it plugged in (I manually move the gripper assembly), . Here is what I observe when I make a selection:

The carriage stops normally, toggle shift goes to the right side, the gripper motor starts BUT sometimes it runs at slow speed. I manually continue to turn the gripper assembly and the switch actuating braket leaves the front of the camshaft switch. At this point, the gripper motor accelerates to what seems to me to be its normal speed.
The arm lands on the disc and sometimes the gripper motor slows down BUT does not cut off, it continues to turn BUT slowly (when at this point, it should be cut off normally)

I have the impression, however, that camshaft switch close and open normally.

So there is something that sometimes makes the gripper motor turn too slowly and also makes it turn even when it should be stopped.


Do you have any idea? Thank you.

[jukenorman]

Hi Cedric,
It's quite difficult to fault find issues like this from afar. The only advice that I can offer is very general and that is to treat each fault in isolation. For example, if the gripper motor is operating when it shouldn't - pull the plug on the motor and trace through the circuit to find the point of failure. Sometimes this is easier said than done of course!

Sorry to be so vague. My suspicion remains that it's probably poor contacts/switches that are the cause.

Norman.

[cedric]

Hi Norman,

Thanks again. I understand that it's not easy. I notice something.

The gripper motor is still dismantled and still connected. So I turn the gripper assembly by hand to activate the cam switch and see what happens. I do NOT make a selection, so the magazine does not turn, so only the gripper assembly is in motion. Every time I start the gripper assembly, the gripper motor runs fine, so it never idles IF the magazine has not been turned.

I continue to search.

Thanks.

Edit: I realise that if I make a selection, and if the gripper motor run slowly, it's because toggle solenoide still energizing also. 

I continue to search.

[jukenorman]

Hi Cedric,
I am a bit confused? If you have the grippper motor off and you operate the gripper assembly by hand, I cannot see why the transfer motor would run unless you activate the stopping switch. The transfer motor always relies on an activated stopping switch to run. Maybe we are getting closer to your problem, maybe there is a wiring error somewhere?

Norman.

[cedric]

Hi Normand,

Yes, as you say, I look wiring, and I see some cables with different colors that are toghether. Welds are not original, and 2 smalls capacitors are there, but nowhere in the manual.
Poor jukebox (especially poor me) it was well massacred on all sides.
I'll check each cable one by one to be sure.
Thanks again for your help Normand.
Have a good evening.

[tvtechrich]

I am having a similar problem with my G200. Maybe 1 time in 100 the gripper will lock up when it starts to grab a record . Turntable still spins, cutoff switch activated ,amp on, going round. Armature locked . Cut power, move by hand and it takes right off. I don't think it's electrically locked, as the fuse will blow if left for 20 min, and it's still locked.
I don't understand how it could be electrically braked, as there are only 2 wires..not field and armature separate . Must be a permanent magnet motor. I think the other poster was thinking of the motor that drives the records basket ,not the transfer motor.Stopping switches shouldn't affect your problem.
I have redone the reversing relay contacts to no avail. I suspect a short to ground somewhere (maybe internal to the motor) that effectively puts AC to the motor.
If you could monitor the voltage at the motor with a meter and se if there is a difference between when it works and not.
It shouldn't be the shifter, because it has to be in the right place to have laid the record down, but maybe a little off?