one head sewing loose

The fundamentals are still all the same. However there are different tips and tricks, and equally different machines are known for their little quirks.

What model/series is this machine? The reason i ask is because of the display panel. Perhaps we can alter a setting to get you a little better results, although if the problem is that extreme, it probably wont do much, but it's worth a shot.

Im in agreement with the others, At first glance. It does appear that it is a timing issue. Is this something that has been getting progressively worse? Or did it all of a sudden just happen? Did something happen to that head, like needle break or really bad "birds nest" did it catch a piece of fabric and eat it?

my friend,did you solve the problem?

sounds to me like needle depth issue or needle-hook gap.. can not be timing because is common for all heads and 3 work fine.
You need to manually go to lowest point and check needle depth. There is a gauge that comes wth all tajima machines to verify this.
Other hint would be to check gap between needle and hook. should be 0.1-0.2 mm. No idea how to check?, turn needle 180 degrees and should touck hook. when done turn needle around to its original position.
good luck!

I would try googling for a service manual for your model machine. Sorry I can't be much more help than that. If you had a Barudan like ours, I could help.

Here is a link to a Tajima multihead service manual. This may not be your model but may give you an idea of what we are talking about.

http://www.hirschinternational.com/Support/Manuals-Videos/~/media/Files/Support/Product%20Resources/Tajima%20Embroidery/MaintenanceGuide/tehx_mh_maintenance_guide.ashx

90deg not 180

to set the distance between rotary hook tip and needle you must use No14(90)needle
rotate needle 90deg from normal position and move the rotary hook to have slide contact with needle.
hook point is 200 deg but depends model
timing means the point where rotary hook tip meet the needle(degrees) .
you can have for one head bad timing if rotary hook was moved from normal position (because bird nest,broken needle....)
is in Tajima book

hirschintl.com
tehx maintenance guide

embroiderytrainingvideos.com for many advices and swf dvd repair.
is not tajima but mechanical many parts are the same
if you will have problems in the future you can ask me

Hook gap or timing? Needle depth adjustment? Don't know on Tajima, but one adjustment effects all needle depths on Barudan. Just a thought.

Did anything happen to that one head that did not happen to the rest of the heads at some point?

like twok4hd said

hook timing (200deg)
gap between tip of rotary hook and needle(aprox 0.1-0.3mm)
needle bar lower dead point

verify if between rotary hook basket and rotary hook support is aprox 0.8 mm space to pass the thread
verify if rotary hook support don t have burr