Constabulary

But the machine has no needle positioner as it seem (see hand wheel) so in this case the white plastic nub has no purpose.

happens when you are not logged in, should be available when you are logged in.

My guess: The black internal lever with the magnet on it (on the inside of the accelerator unit) which is attached to the external lever where the pit man rod is attached to (other side is attached to the foot pedal) has shifted and the magnet no longer is aligned with the hall sensor. That probably happened due to the bumpy roads you drove. Just my guess. Assuming it looks similar on your motor - see pictures:

maybe this manual will help. According to this manual PD seems to be a "pedal warning" Servo Motor Technician User Manual(v3.7 L-Type 4-Bar for ShuangZheng).pdf

a personal comment suits better here I´d say. I never hit any like or dislike button - no matter where. But I´m Generation X and not very social media affine anyway.

Yeah, I´m shy with saying so 😁

Patcher machines are designed as repair machines and not for producing goods. Keep in mind hat the 29-4 is a century old machine (or older) and they have tiny bobbins that do not hold much thread and the older the 29 / 29K is (the lower the subclass number the older the machine - basically) the more wear they have and wear parts are hard to find for the early 29 / 29K. This may help you to figure more about the 29-4: https://www.google.com/search?client=firefox-b-d&q=29-4+site%3Aleatherworker.net

The Textima 17 is a clone of the Singer 17, made in east Germany after the War at around the early 1950s. Not really a heavy duty machine and the bobbin size is quite small. Pfaff 335, Adler 69 come to my mind. Adler 5, 105 or Singer 45K are way heavier but are drop feed machines, some may have a jump foot. CLAES 233 may be something to look for they were quite common in the former East Block and are excellent machines.

I would like to buy that sucker but wrong side of the pond - too bad. That basically is a cylinder arm version of the singer 457G / 457U I´d say. And going back in history I´d guess it comes from a Singer 107w50 - kind of and I would guess the two share some accessories. (Singer crazy me is 😜)

Do I get you right, you cannot adjust the stitch length, right? Or does the feed do not come high enough out of the needle plate? Please post pictures of your machine.

Have you read the above linked threads? You do not necessarily have to machine needle bars. If you have the 2nd type 51w (you have not posted pictures yet - I´m not sure if there was a 28 subclass in the early and late 51w model line) the NB diameter is 6.35mm / 1/4" so you can use a Singer 111w needle bar (for triple feed machines) and shorten it as needed and you can use 135x17 or 135x17 needles. 111w NB just cost a few bucks - sample: https://www.ebay.com/itm/162129813710 If you have the 1st type 51w (the one I have - see above thread I have linked) you can use a 111w needle feed NB (Singer # 240020) which has ~8.74mm diameter. But then you have to alter the lower bushing (add a longer one) or add a bushing at the top (that what I did). This may help you or not. Just meant as alternatives to a custom made needle bar. 😉 BTW: This is so far the closest manual for the 1st 51w I could find (see attachment) The 2nd type manual is already linked above. This is the bobbin for your machine if it still has the OEM hook https://www.ebay.com/itm/162656003877 If the needle bar "challenge" is not what you want then your machine ex factory is using needle system 128x2 / 128x3 (short needle with thin shaft) sample: https://www.universalsewing.com/sewing-needles?needle-system=128x20 Singer 51w100 and 52w100 - instructions for using and adjusting(1).pdf

There is an earlier type 51w based on Wheeler & Wilson and a later type 51w and the two types are using different needle bars and are mechanically different too. So it depends on what you have. I assume you have the earlier type 51w. This thread my help: https://leatherworker.net/forum/topic/96574-singer-51w56-needle-bar-conversion/ Some years ago I have restored an early type 51w and converted its needle bar and I still have the machine. https://leatherworker.net/forum/topic/86292-singer-51w-sv-2-post-bed-machine-restoration/

looks like a Durkopp 291

If you are a DIY guy you can make one your self. I once made one for my Singer 45D91 but the Idea was stolen from LW member UWE. Just an idea. 😉

Well, de do not know the details of your machine cause we are not in front of it. So picture may help us to figure things. Have you pulled out the stitch length spindle? There is a pin on the inside oft the dial knob that pin goes into the coarse threading ion the top shaft. You have to push the spindle a bit when "screwing in" the spindle. Do you have a manual for the machine If not here is one. See pages 18, 19 for an x-ray view of the stitch length assembly. Hope this helps a bit. 107W1,W3,W5-inst.pdf