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FrozenGate by Avery

532nm pot mod on non-adjustable driver?

sportcoupe

sportcoupe

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I have two cheap ebayser 532nm pointers. I opened them up to try the pot mod but found no pot.  :-?

OK, the output is set by a SMD resister. Which one? Here are pictures of both sides of the driver board.

switchside.jpg


noswitch.jpg


backside.jpg


nochip.jpg
 





I tried to trace the circuit from your photos but it doesn't make any sense. The only part I'm sure of is Q3/R10/(R7?) which is the direct laser driver and R2/R3 which is some kind of closed loop feedback for the driver part (not the sense part). R5/Q4/R4 seem some kind of pre-driver parts, also nothing to do with the current.

I can't see what happens close to the laser because of all the glue. Can you remove that?

I also can't see where one wire of R11, R2, R4, Q1 and pin 2 of the IC lead to because the traces disappear under the IC. Maybe you can measure which ones are connected to which IC pins or possibly to each other.
 
I changed the pictures in the first post with the new cleaned up pictures. Sorry they are not super clear, I took them with my phone. Hopefully it will make some since to an electronics expert now that the glue is removed.
 
Ok, I came as far as figuring out it is a switched mode boost driver, but I still need those connections which go underneath the IC.
 
That was unexpected (in two ways). I didn't know you were this experienced in soldering. I wouldn't even have done that, but my approach would be totally different. (measuring traces in all kinds of combinations to find the connections, not by disassembling)

Well, now I still don't know the traces. The unexpected vias under the IC lead to under the switch. Can you remove that too? I know I may be asking a bit much, but seeing you went as far as removing the ic..

About the phone sharpness... In such situations I usually take like 6 or more pictures at different focus, and later I choose the best one.

I already found the datasheet. I wish i could know more about the Q's, as two of them seem to be a Zener or other kind of diode. NO part numbers though because the codes on the case of sot23 are always abbreviations (would become too small for a whole partnr) used just to distinguish different parts during building.
 
I consider myself an excellent solder tech. I do not know enough about electronic circuits to design from scratch like you are doing in reverse for me. I will remove the switch tomorrow and post another picture.
 
doing it in reverse... 'scratch from design'? Sounds about right.
 
That's exactly right, "scratch by design". LOL.

I uploaded a picture of the switch side with the switch removed.
 
This is as far as I got.

ebayzer.png


Either they are abusing the opamp IC or I've missed something. R11 and R6 just are just connected to the inverting input of the opamp, even though good design rules state that the opamp shall not put a load on any load attached to the input. In other words, the input could just have been connected to gnd.

It also dawned on me that RE1 is a missing potmeter, which supposedly either lowers the value of R11 or replaces R11.

Can you see, with a loupe, if pin 1 and 2 of the IC are connected? Either way, it does not explain the significance of RE1. My best bet, at this point, is that increasing the value of R8 will increase power.
 
I dug up my loupe and checked the pads of the board at pins 1 and 2 of the IC, nothing there. I used my Fluke meter to measure accross the pads of pins 1 and 2, I measured just over 4 meg ohms. This is with the IC still out of the circuit.

I may try increasing R8 some just for kicks. Would 10% be enough or should I go all out and remove R8 for wide open circuit for max current output? Remember this is a cheap pen laser I don't mind breaking.
 
You could start by soldering wires on those pads and attach a potmeter if you have any.
 
I removed R8 and soldered on wires connected to a 10k pot. I went through the full range of the pot and noticed nothing different. I then lifted one wire off the pad making a complete open circuit and again noticed nothing different. The dot on the wall never changed in brightness. Oh well. I am not disappointed, it was all for fun.

+1 rep for you Zom for all your help.
 
it's probably the resistor across RE1, where the pot would normally be. Try lowering or raising the resistance, or add in a pot there (the contacts are already there, just remove the resistor and solder it on the board). That should do it
 
Seems like a lotta work for potentially NOTHING. you could end up instantly toasting the diode by overdriving something that just isn't designed to be overdriven. Kinda the reason I no longer pot mod my green lasers. too many times I end up killing them. well there's a wasted laser!!!
 
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