Maker Pro
Maker Pro

Transformer Ring Tester


Oct 5, 2014
Oct 5, 2014
Built up the "in circuit" version of this ring tester however when used on several different 220v iron core transformers and one ignition coil, cannot get anything near the number of "rings" they show in the video. I get sometimes a 0 reading and on others, perhaps 1 if I'm lucky.
It is in broken English from a Czech guy but easy enough to follow his explanations.
His web site with details is here........ ...and the associated video here......

So I thought I'd go back to his "beginning" model for "out of circuit" testing but get the same results.
Again, his web site for his first, simpler, out of circuit unit is here...... ....with that associated video here.....

On this version he shows how to lower the sensing level for perhaps more rings or how changing the cap to up to 1uF can improve the unit but nothing seems to make any difference.

I was thinking perhaps it was meant for ferrite type cores rather than iron core and thought i'd run it past you guys for any comment.
I've probed the relative points for a signal (with a small DS150 scope) which should mimic his videos , at least somewhere near but no such luck.
Caps in use are low ESR as he says is necessary, well actually he says low dissipation factor which to me at least, from what I can gather online, seems to follow along with low ESR.

There are both the hex files and the assembly file for each but I'm not up with assembly so doesn't make too much sense I'm afraid.
I checked the signal out to the mosfet which appears in line with what is supposed to be programmed in but have no way to check if input level sense is actually set correctly.
AS I say, the rings on mine seem low both in number and in voltage level in comparison.

Using my old "Dick Smith" LED ring tester, I get good rings on the same iron core tranny's.


  • Schematic.jpg
    81 KB · Views: 4
  • First Unit.jpg
    First Unit.jpg
    60.4 KB · Views: 4
Last edited: