Is there a way to test whether or not a 7135 is working as intended without desoldering it from the 105c driver? And also, once desoldered, what is the test method? Perhaps resistance across two legs…something like that?
Please see information regarding my issues here: Solarforce K3 Modded & Compared - Pics w/Vid *Pic Heavy*
I tried to perform the MT-G2 zener modification to a QLite 105C, but as you will read, things did not turn out as they should…
Did you remove the polarity protection diode, and replace it with a 200 ohm SMD resistor?
Check continuity on the chips first. They are all in parallel so left pin to left pin middle pin to middle pin, right pin to right pin. Do that for all the chips on both sides. Resistance should be 0 ohms. Resolder any pins that aren’t connected. If you’ve got continuity to all pins then unless you want to remove chips one at a time and test output each time until you’ve removed the bad chip you’re better off just using another board. Do the testing though. It’s good practice.
I’m a bit of a hacker at adding chips, so after each chip, I hook up the driver to an emitter and take a current reading. The current should increase by around 350mA. If it doesn’t change, double check it for continuity.
+1… just take an accurate current draw reading. Even a poor meter will get you in the ballpark of measuring 1/3A variations.
Since the 7135 drivers do not boost or buck input, you are getting a real current reading. The only time you get a bad reading is if the battery voltage drops below about 3.2V. Just make sure you are providing enough head room (3.5V or better preferred) to fully drive the emitter.
Remove the zener diode and test it with a single cell/3v LED.
Thanks all for the tips. I had done all the recommendations before, but redoing them was a good sanity check.
I went as far as removing all the 7135s i added to bring the driver back to stock form. This changed nothing.
I also replaced the Zener diode (the one i added for MT-G2 use), with another fresh one… also nothing…
I then removed R1 (low battery voltage resistor) per RMM’s suggestion… unfortunately still the same issues.
Conclusion: Defective driver. Will try again with a fresh one