BLF-A6 driver repair.
In the process of installing a bleeder resistor for a lighted tailcap mod I managed (or it managed itself, dunno how it happened) to damage the driver of one of my BLF-A6 lights: in the 7 modes setting without memory, the first three modes became the same, quite bright, it looked like the 7135-chip did not respond to the MCU anymore and was always open. Today I spend some time (hours actually, I'm glad this is a hobby) repairing it. I took the driver out and clamped it in the vice, with the ledboard re-connected loose in the air for testing with a 18650 battery. First, I tapped all the solder joints on the driver with the soldering tip to make sure no cold solder joints were leftover. Did not help. Checked every component for shorts underneath, no luck.
Then I swapped the 7135 with another one from the spare parts box. Now something did happen: very weird behaviour: very dim light from the die (like: 1/1000th moonlight), and after tapping the battery connection (=switching on/off) a number of times suddenly full blast, then extremely dim again. I tried another 7135 from the box. Now an almost complete user interface, just the moon was much lower than stock. Then I tried a few other ones and mostly got this version of the UI with extremly low moon, and in the meantime I began to watch the lettering on the chips: 35A,35B,35C,35D,35E,38A,38N, what is the difference?. There are more 7135 versions than I already thought:
(I have a few more types actually, but could not find them back for the picture). Then I soldered the stock one (the one in the bottom right corner on the picture) back for a check, and it was indeed still broken: all 7135-modes were still max. I already decided to settle for the 35D because it had the most usable way too low moon, when I thought of digging into the complete drivers box for more variations of the 7135 and sure enough I found the same type of the stock BLF-A6 driver on an ancient 2x7135 1-mode driver from dx. Tried that one and presto: the UI is back to normal, the BLF-A6 apparently needs this specific chip.
Morale: I don't know if this has already found out before, but there's clear variations in how differently marked 7135-chips react to (at least) the BLF-A6 firmware