Circuit operation and component substitution questions for stroboscopic timing light
Is there anyone who can give a piece of advice?

There are some guys on her that are very good with transistor circuits, but I'm not one of them.  In my 40+ years I have never designed a circuit with a transistor.  My experience with transistors is from a class I took in 1974.

I used a Nichia NFSL757GT LED, and I've regulated the current with two
220 ohm resistors in parallel. Is it OK?

It's okay, it will light up but it's a mid power LED capable of 180 mA so I would add another resistor or two (in parallel with the other two).  It not a particularly good choice.  I would use a high power 5700K or higher cool white.  With a spot lens.

Do you think it is working properly?
Instead of the BD135 BJT, I've used a FZT651. Is it OK?

I'm going to go with a no on these as a BD135 is an NPN and the FZT651 is a PNP.

is C1 a 220nF capacitor?

Yes, most likely guess.  µF would be too big and pF too little.

R1, D2 and C1. The author wrote that they protect the thyristor, but
what does it mean?

The trigger signal is likely to have transient spikes that exceed the rating of the thyristor. C1 absorbs excess energy, the D2 redirects excessive voltage spikes to ground and the resistor is used to provide the voltage level required for the thyristor given the trigger level.  I'm almost guessing.  You seemed desperate, I tried.


I do know LEDs very well and I have used a Snap On timing light.  It was much brighter (xenon flash bulb) than a single 30 lumen mid powered LED.  And it had a lens.
If you do not want to use a SMT LED and lens,  then use a 30¢ Cree 5mm Round
LED part number: C503D-WAN.  This has a 15° lens with 45,000 mcd of cool white which would equate to 2,400 lumens.  Your Nichia is about 30 lm @ 120° and is a warm white.  This app needs a cool white.