I have a 17mm fet driver that I ordered from mtn that has a zener mod for a 6v led with the use of two cells. It’s supposed to have Guppydrv Rev2 but I only get one mode out of it. It does the same thing when I test the driver outside of the light. Maybe a few of you driver gurus out there can bestow some of your knowledge upon me. Here’s a couple of pics of the driver…
If the black wire is shorted to ground side of R2 then it’s bypassing the fet and no modes.
You fast press it 8+ times and it won’t blink for program /mode change?
Man I can’t believe my eyes are that bad…desoldered the ground wire, resoldered it and I still have just one mode. Did I burn something up?
No sir, no worky.
If you have a dmm check continuity between led - and gnd. Also between fet gate pin(closest to driver center) and pin 6 of the 13A mcu(pin above “14” in atmel 1421). First should not be connected and the second should. After that run home to Rich with your tale of woe.
With no power applied, measure ohms from LED negative to the ground ring.
With the light on, short the FET gate pin (red arrow) to ground, see if it turns off. (EDIT: First make sure the gate pin isn't accidentally shorted to the LED+ pad!!!!!)
Never ever had that happen and I have gone thru quite a few of Richards FETDD drivers? But anytime I ever had a problem, replacing the FET always worked. Just curious what mode do you have Turbo? Sure your not grounding out to the (-) lead ?
I can guarantee you it’s not on RMM, I’m sure it’s something I’ve jacked up. This is in an L2 with an MT-G2 and this guy really only wanted one mode anyway. My eyes suck too bad to even see that stuff to test it, lol…so one mode it is.
Well, if there’s a short bypassing the fet or disabling the gate the you won’t have any LVP to let him know when to change cells. If the OTC cap is fried would that cause it not to recognize a short power interrupt? I.e. Cap is shorted or drains too quickly.
I guess I need to start reading up on all the components of drivers so I understand how they work because driver stuff is like a different language to me.
You don't need to know all that, just check the things that have been mentioned. Basic multimeter checks. Is X shorted to Y? Is there Z voltage at pin whatever?
Linear drivers(FET, 7135) are the least complicated and most straight forward since the current in equals the current out and there is no adjustment to the voltage. The brain (mcu) in your case and many others is the attiny 13A chip and sends a signal to the the FET telling it to turn on and off very rapidly for varying lengths of the on cycle. This is called pulse width modulation (pwm). The eye normally doesn’t detect the pulses unless illuminating a moving object like a fan or rain drops but the variance in on time shows as more or less light. That’s it as far as led control. The Zener diode limits input voltage to something the mcu can tolerate. R1/R2 are a voltage ladder that allows the mcu to detect low voltage from the battery, and the off time cap changes how the mcu sees power interrupts for mode changes. If the off time capacitor is damaged then the mcu might not be able to detect the half presses used to cycle the modes. I’m definitely not the sharpest knife here but after a few years it does start to sink in.
Simplest thing to check — where the black wire contacts the LED star, is there any bit of wire or solder that could short that out to the body of the flashlight.
That’s been the cause of this problem on lights I fiddled with, three times out of three — a bit of mising insulation where the wire comes up and bends over to be soldered, or some little whisker of solder or one fine wire out of a bundle grounding the negative right at the LED.
He said it happens out of the light so I assumed the mcpcb itself isn’t grounded otherwise that or also an led minus pad to center pad short would be a possibility.
