EME-155 stepper motor only moving the reader head outwards.

[oli71fr]

Hello everybody, 

I have been lugging my CPC6128 around Europe and we are now in Estonia, where it was stored for a while.

All works except the drive, and it is the stepper motor that is troublesome. 
The belt was replaced in 2012 and it is still OK.

I have taken it apart, having previously marked its position but it stubbornly wants to turn only one way bringing the head outwards from the disc centre.

I am wondering what can cause this.

I am thinking that it is possible all the connections on the motherboard where the FDD cable attaches are not all continuous, or 

the other possibility is if the wires are not connected correctly or disconnected on the edge of the motor itself. 

Maybe I should post a video. It will speak a 1000 * 1000 words.

None of the wires are sticking out and all the solder points look clean with no cracks, I have "wetted" all connections and checked them with the multimeter for continuity. 

The drive detects files on the discs with CAT, but this can only be done once by sliding the head down manually and letting the step motor bring it up to the top, and it does not necessarily repeat because as the head goes up it puts itself out of sync.

It is as if the information for the head to go down towards the centre of the disc is inverted and pushes the head outwards.

I am dismissing belt or RPM issues because the drive still reads using CAT, maybe I am wrong in that assumption.

The Drive is an EME-155.

Thanks in advance for any comments. It is fantastic to have such a community.

[Bryce]

Check for dry solder joints on the connector sockets to the motor.

Bryce.

[oli71fr]

Hello Bryce, and thank you very much for the super quick response.

I got hold of a soldering iron and I wetted the solder of these 4 connections and they are continuous.
I will go through this checking again to make 100% sure and verify continuity to the motor if I can reach it.

Do you mean the connections on the motor itself (all 4 are in a square attached coming out the stator with transparent ends)? - I am a bit loathed to pulling these out as I have no way of seeing how the wires are attached to the motor.

Best regards

Olivier

[Bryce]

No, I meant the connectors on the drives PCB. They are small white headers and are known to fail. Also check the solder joints on the power and flat cable connections on the drives PCB.

Bryce.

[oli71fr]

Hello Bryce

I checked for continuity at all the locations shown in the Flickr links below :

Stepper Motor cable socket on the drive board
https://www.flickr.com/photos/monsieurbond/52275896427/in/album-72157638710759703/

Main cable and Power cable attachment pins
https://www.flickr.com/photos/monsieurbond/52276869911/in/album-72157638710759703/

Stepper Motor Cable ends
https://www.flickr.com/photos/monsieurbond/52276869981/in/album-72157638710759703/

I also took the soldering iron to wet the locations.  The other side of the board looks like this
https://www.flickr.com/photos/monsieurbond/52276039772/in/album-72157638710759703/

The continuity is there. I also took the mainboard out to check for any issues, but I could not see any with the magnifying glass

As soon as the videos have uploaded, I will add the links to this post.
Video1
https://www.flickr.com/photos/monsieurbond/52276081467/in/album-72157638710759703/

Sadly I still have the erratic movement of the Head issue.

Thanks for the help so far.

Best regards

Olivier

[Bryce]

Did you re-solder the connections on CN3/4/5/6 on the bottom of the board? It doesn't look like you did in the picture.

Bryce.

[oli71fr]

Hello Bryce, thank you.

I am quite certain I did, but I will re-do those as soon as I can, just to eliminate them. 

I definitely did CN6.
Should I add more solder? At the moment I just touched the solder to liquefy it and leave as soon as it emits a puff of smoke.

Best regards

Olivier

[Bryce]

You have to add more solder, not just melt them. New solder contains flux, the old stuff doesn't.

Bryce.

[oli71fr]

Thank you Bryce, I will do that next.

[oli71fr]

Hello Bryce

Firstly I wish you a happy new year and I hope you will have a great new year's eve.

------------

So, I found some time today to ad solder to the board's connections for the stepper motor cable
https://www.flickr.com/photos/monsieurbond/52597195457/in/album-72157638710759703/

The connections of the other components
https://www.flickr.com/photos/monsieurbond/52598203263/in/album-72157638710759703/

The main electrical feed
https://www.flickr.com/photos/monsieurbond/52597195392/in/album-72157638710759703/

I know they don't look as good as before but I did the checks to make sure there was no solder connecting 2 places.

Sadly the situation as not improved and I am running out of ideas.  the motor is not turning and looks as if something is blocking it. Although after a quick strip down and rebuild I found nothing that is blocking any movement.

I have no idea what else could cause this.

Best regards

Olivier

[Bryce]

You may have this issue: https://www.cpcwiki.eu/forum/amstrad-cpc-hardware/fixing-a-floppy-stepper-motor/

Quite a complicated repair unfortunately.

Bryce.

[oli71fr]

Hello Bryce 

There is no rubber piece at the top, I cleaned it off thinking it was dirty smudge from dust and lubrication.

I wonder how the inside of the stator looks like when operative with the rubber piece in.

The rotor and screw drive are solidly linked, there is no dislocation possible there.

 I have kept seals from coffee machine repair, with some tweaking they may fit (loosely), although i am not sure the rubber should isolate the copper springed support that is at the bottom of the stator housing.

Maybe there is a fault on the board. I have checked for continuity but I have not checked the state of the electronic components.

Fully functional FDDs dont seem to hard to get on Ebay right now.

Best regards

Olivier

[Bryce]

It will work without the rubber if the leaf spring at the bottom of the stator housing is pulled upwards to give it more tension.

Bryce.