# Brother PR620 Troubles where is the thread break sensor?



## lowriderchris (Feb 26, 2011)

Hi ive got a pr620 and it stitches about 10 stitches and then stops giving the check upper and lower thread error even tho there are no breaks and the stitches are good so I think there is a fault on the thread break sensor if there is one? or I could be well wrong, ive done the usual maintenace and rethreaded checked tensions ect also it does it on all needles which rules out alot of things. 

Can anyone shed any light especially to do with a thread break sensor or similar?

many thanks


----------



## coolbeansgifts (May 24, 2010)

Hey Chris.. I am sure you have already did the tension check on the bobbin. We have a PR650 and I check it with the weight provided with the kit and I once the bobbin housing that would not seem to adjust to flow thread evenly with weigh and having a simular problem as you, although not as often. I Ordered another housing and it worked great.We have had some bobbins that had too much thread on them and did not flow well until we pulled the extra thread off the bobbin. All this may be elementary to you, however maybe some of these old heads can offer you something more worth while.

good luck

David


----------



## imeccentric (May 13, 2007)

Thread break sensors are needle specific so unless you have all of them threaded incorrectly , that isn't it. But, you can try wrapping the thread around the sensors, (the knobs on the top ) twice instead of just once. Be sure the thread snaps into place correctly(that would be my first thing to check). Also, and it sounds crazy, but a ceiling fan or ac blowing can affect tension on those things. If this is only happening on lettering, your entire tension may not be correct as it is critical on that machine. I do agree with David on the bobbin that has too much thread. I've had that happen on several boxes before.


----------



## zoom_monster (Sep 20, 2006)

Jim's got it... The way the machine "sees" if the thread is broken is if the wheel is turning (or tap bar on Amaya). If the wheel is not turning, then the thread is either not wrapped around it properly or the tension that lets the thread grip that wheel is too low. sometime if you switch to a rayon(more slippery) or a thinner thread this will cause the wheel to not turn. Smoe machines allow you to adjust the sensitivity, but start with the path and the tension first.


----------



## ikkuh (Apr 8, 2010)

Or just get the tension knob completely loose and pull i apart.
Clean the disc and screw it together again, then adjust youre tension. It worked for me some time ago, i had some lint in the disc so it became slippery. But if all the needles have this issue, i dont think it is a sensor problem.

also check under the needleplate and clean it, there might be an awfull lot of thread there causing this tension problems.


----------



## lowriderchris (Feb 26, 2011)

an update its not all the needles I completely misunderstood my partner its always number 1 and now started on number 3 I have a pr620 and 2 pr650's ive cleaned the felt discs and readjusted the tensions ive cleaned under the needle plate blown out and oiled, changed the needle taken the case off around tensioners and made sure all the ribbon cables are in ect I even swapped the felt discs and metal discs around from the faulty needle to a working one and it made no diff and ive used a bobbin case from one of my 650's and that didnt work either...

should I swap 2 of the thread break sensors over? from needle 1 to needle 6 for example? 

any idead now ive said its not all the needles sorry about that


----------



## lowriderchris (Feb 26, 2011)

ive also tried wrapping it around twice, thanks for all your suggestions so far


----------



## imeccentric (May 13, 2007)

Chris,
The discs can lose tension sometimes, but it is rare in my experience. It's sure worth a shot. I know during a tune up, they are usually replaced. Are you using anything new or different? A new lot of bobbins, or thread? I have heard some people have more trouble with black thread than any other. Wish I could help more, but maybe there are more savvy sewers out there who will chime in.


----------



## lowriderchris (Feb 26, 2011)

Thanks for your fast reply Jim im using the same threads I have for years and ive tried it with numerous colours and re-threaded it so many times Ive already tried swapping the discs over im now thinking about swapping the electrical part under the tensioner to rule that out have you ever heard of this failing?


----------



## sassystitches (Sep 16, 2010)

I have a similar problem on my PR-650, mine only happens on needle 4. At first we thought it was just a cleaning thing because it needed cleaning and servicing bad. After we got it back from being serviced it ran well for a few garments and then back to showing a thread break on needle 4 randomly. I am following this thread for more information myself.

Edit: by the way, we didn't have them look into it because I just (wrongly) assumed that it was because it was dirty and that a normal servicing/cleaning would take care of it. My lesson: should have mentioned it to them so they could have at least checked into it further


----------



## imeccentric (May 13, 2007)

Just did some quick research and it seems there is a trouble shooting sequence for this problem. It can be caused by thread quantity sensor, bad leads or connections that have worked loose, and a head pcb or main pcb (control boards). Do you have the shop manual for checking these?


----------



## imeccentric (May 13, 2007)

If you completely disassemble the top tensioners, and remove the cover underneath of them, turn it over and you will see the thread sensor pcb and head pcb. Chances are, that is where your problem is.


----------



## lowriderchris (Feb 26, 2011)

no I dont have the shop manual for these machines do you know where I can get hold of a copy? ive have the cover off the tensioners today and seen the head pcb board all the cables seemed tight in there seems strange how its contained to needles 1 2 and 3, number 1 continuously and 2 and 3 intermitant I think I may take the complete top cover with tensions and pcb from one of my 650's and put it on the 620 and see if the problem persists what do you think? what does the trouble shooting suggest to try?

thnakyou for all your help


----------



## imeccentric (May 13, 2007)

Join this yahoo group, and go to the file section. They have complete parts and service manuals (the same ones the techs use). 
PR600-EmbPro_Machines : PR600 & Embroidery Professional Machine Lovers
Your trouble shooting section is in the last group and the thread tension section is on page 35 in part 2.


----------



## sassystitches (Sep 16, 2010)

Thanks for the info Jim. I just went and downloaded it. Maybe I can find something to help me.


----------



## MARCEL10 (Nov 3, 2010)

I'm new to this website.I going crazy with my pr-650.i also have the same problem.On my needle 2 it stitches about 15 stitches and then it stop working.the error message comes up to check upper and lower thread.I basiclly did almost everyhting that i could think of and still no luck.
Please anyone can help?
thank you


----------



## tfalk (Apr 3, 2008)

If it's only that 1 needle, either it is not threaded correctly or the sensor is bad... I find that happens mostly when the thread isn't completely under the first gate at the back of the machine or it threaded around the post instead of the wheel under the tensioner.


----------



## xfuture (Oct 4, 2014)

Any update on this? I am having this problem out of the blue on all 6 needles on my PR machine. I need to replace the main board I think...


----------



## jimcr (Feb 3, 2009)

This can sound really stupid but I have done it and so has my wife , make sure the bobbin is in correctly , Sometimes it will sew for a while with the bobbin in backwards. Also check your bobbin case for wax build up under the spring.
Wax/crud can build up and decrease the tension and cause the same problem.

Sometimes it can be as easy as changing the thread to a different needle as one is just too sensitive for the thread or the thread is old.


----------



## xfuture (Oct 4, 2014)

I've had that happen and this is different. it was working fine then all my needles had the check upper and bobbin error. made 50 caps no problem with this same spools of thread and same type of bobbin...


----------



## vicman962 (Jul 16, 2013)

hello, my pr- 650 sends message pcb reset and stops, I have to give it start again , someone can help me, thanks


----------



## Lawllt (Dec 11, 2016)

I've just joined this group and I have the exact same problem. Did you find a solution?


----------



## GBBikeLeathers86 (Dec 17, 2017)

OK guys!
I know this is an old thread (no pun intended) but My machine has developed the same problem on number 1 needle. It kept stopping for no reason drove me crazy for 3 days!

I read the thread on here then had a look at my machine.

Yes the sensor is under the thread knob tensioner on the top of the machine. yes there are felt pads but what you have all missed is the way this device works! did you notice the round magnet? the thread pulls the wheels around ever time the machine does a stitch the magnet creates a pulse that a sensor coil underneath the plastic disc that will be left on top of the machine detects, after removing the knob spring bush and felt wheels.
So what was the problem with my machine dust and a minuit piece of thread less than 1mm in length. This was blocking the magnetic field generated by the magnet from getting to the pick up coil. 

Clean all dust and any thread off the plastic plate! reassemble reset the tension and the whole 16000 stitches stitched out with out stopping.

I should have gone to speck savers sooner and had a look! LOL


----------

