Pfaff 335 h3 doesn't sew properly

[jimi]

I think the parts were maybe changed or this is not a pfaff tension assembly, anyway the first post where the thread passes on the assembly is not the same? you have the thread outside on the pin instead of inside the small ring?? See 1st red arrow in the pictures.

[Gia]

4 hours ago, jimi said:

I think the parts were maybe changed or this is not a pfaff tension assembly, anyway the first post where the thread passes on the assembly is not the same? you have the thread outside on the pin instead of inside the small ring?? See 1st red arrow in the pictures.

here is a better picture:
 

I did the threading following its manual.

[Pintodeluxe]

It doesn't look like the thread is snapped behind the pre-tension disc before the main tension discs.  

Additionally, if you need more upper tension you can thread right to left through both holes leading up to the pre-tensioner disc.   

[Gia]

7 minutes ago, Pintodeluxe said:

It doesn't look like the thread is snapped behind the pre-tension disc before the main tension discs.  

Additionally, if you need more upper tension you can thread right to left through both holes leading up to the pre-tensioner disc.   

I'll try, thanks.

My main problem was that the machine doesn't stitch at all or when it does, it looks like in the pictures. 
Given the fact that the timing is perfect, could the tension be the reason why it punches the leather without making any loops?

[Pintodeluxe]

If the thread was forced into the wrong slot, and not really threaded correctly, it would certainly cause problems.  You were right to suspect timing issues.  That's the first thing I'd check if it wasn't forming stitches at all.  If it's leaving loops on the bottom, you need more upper tension.  Assuming the bobbin tension is okay, try rethreading it, and make sure the thread snaps in the pre-tension disc.  With Pfaff's you can actually hear it snap into the disc. 

 

If you're out of tension disc adjustments, then look to add more passive upper tension IE: go through both guide holes before the pre-tension disc (threaded right-to-left on both holes).  

Good luck with it.    

[Gia]

57 minutes ago, Pintodeluxe said:

If the thread was forced into the wrong slot, and not really threaded correctly, it would certainly cause problems.  You were right to suspect timing issues.  That's the first thing I'd check if it wasn't forming stitches at all.  If it's leaving loops on the bottom, you need more upper tension.  Assuming the bobbin tension is okay, try rethreading it, and make sure the thread snaps in the pre-tension disc.  With Pfaff's you can actually hear it snap into the disc. 

 

If you're out of tension disc adjustments, then look to add more passive upper tension IE: go through both guide holes before the pre-tension disc (threaded right-to-left on both holes).  

Good luck with it.    

I had rethread it many times, added tension, the timing hook is ok as well but this is how it sews:

 half holes half stitches..

Edited July 6, 2020 by Northmount
replaced 3rd party links with the pictures

[Pintodeluxe]

This is the picture that had me worried.  Immediately after you go through one guide hole it doesn't look like the thread is snapped down into the groove.  It looks like you need to move the thread back towards the tension assembly plate to find the groove.  If you make that one mistake, upper tension will be all over the map, and would explain the erratic stitch formation.  

[Northmount]

@Gia Please upload your pictures to this site rather than to third party hosting services.  When files are moved/deleted, or permissions are changed, or host decides not to allow them to be used in this manner, the thread becomes useless without the photos.  I have copied your photos and uploaded them here.

Tom

 

[Gia]

Just now, Northmount said:

@Gia Please upload your pictures to this site rather than to third party hosting services.  When files are moved/deleted, or permissions are changed, or host decides not to allow them to be used in this manner, the thread becomes useless without the photos.  I have copied your photos and uploaded them here.

Tom

 

I will, thank you!

[Northmount]

Have you had  the plate that surrounds the feed dog off?  Does the machine make a noise that is different than what it used to be like a twanging noise?  When you turn the wheel by hand, does it get hard to turn with each stitch, right from the first stitch?

Tom