Easiest way I’ve learned to desolder chips is to cover all 3 pins with solder and when you melt that they all soften together then slide the chip off the boards.
No bibihang. I bought my AWG 16 wires from a local store. The banana plugs I used was from old test lead wires. Banana plugs are the the ends of your test lead wires that you insert into the DMM slots.
Sorry, I forgot to mention that both the earlier and 2nd board were 3.04A boards from IS, so they had 8x7135 (380mA versions).
The 2 7135s that that I added to the 2nd board were the 350mA 7135s.
I ran out of the 380mA 7135s earlier (and now ran out of the 350mA ones also).
EDIT: I started harvesting 7135s from the 1st board, and got the 2nd one up to 4 amps (from the bench supply), and only left it on for a second or so, but then later, when I tried to power the driver+emitter up, it doesn’t work anymore :(.
Something I’ve been wondering about. I’ve been reading how everyone keeps getting higher current reading from their DMMs by upgrading to shorter, thicker wire. Wouldn’t the truest reading of your drivers output be if you were using leads of the exact same gauge as those on the driver and emitter wires?
Ouchy, see this related post.
Testing using the best possible setup will give you an idea on what current your driver can deliver. If you’re not getting the expected current then it must be something else (battery, switch, wires, heat …).
So, I’ve visually inspected the board very carefully, both top and bottom, and I don’t see anything wrong. No solder bridges, no missing joints. Everything looked ok.
Putting the driver on the power supply, I am measure correct voltage when measuring voltage across the negative ring on the spring side and the + on the board.
When I apply power, and measure across the emitter, it’s showing like 0 - 0.02V.
The driver board appears to be dead, but I’m not sure what else to check?
Need pics to spot a problem. Otherwise can only assume toast. If the mcu is fried you can jumper from led+ to any Vdd pin and have a single mode regulated (high) board.
I’ve been doing the above testing, and connections all appear to ohm out all right.
However, what I’m finding is that the Vdd pin of the AMC7135 chips, which are all tied together, are at 0V all the time, even when I have the board powered up from my bench supply. The Vdd pins appear to be coming from pin 6 of the MCU, so presumably that is how the MCU controls whether or not to drive current to the emitter, so it’s looking like the MCU is dead?
Power to the mcu goes through the reverse polarity diode next to led+(red wire). Check voltage there as well. If that’s ok then yes, the mcu is fried. Try a bit less flux or clean it off as it can block test leads from making good contact.
If it is the component I circled, then the end nearest the red emitter lead is showing input voltage (e.g., if the power supply is 3.65V, then I see 3.65V at the end of the diode nearest the red lead).
The other end of the diode shows 0V.
The markings on the diode has “||| S4” with the “|||” (3 lines) away from the at the end of the diode that is away from the red lead.
Is that diode bad then?
I can try to harvest the same diode from another board?
Or, can I just short across that diode, just to see if the driver starts working again, and then harvest/replace the diode?
Short the diode to test your mcu.
If it works then replace the diode for actuate low voltage detection (presuming the mcu is programed for that). As long as you don’t use batteries over ~4.2v and don’t care about low voltage detection or reverse polarity protection it will be fine bypassing the diode.