DIY KL1 biasing mod: quick tutorial + PICS

This mod is VERY easy. All you need is a soldering iron, a steady hand, and a couple resistors.

1. Open KL1 head and reveal the circuit

2. Take a resistor and solder it parallel to the circled resistor.

CM says, The latest version uses a 0.68ohm sense resistor. For 750mA, you need a one ohm resistor in parallel with the 0.68ohm resistor. I just stack it on top of the existing resistor.



I used two 1.5 ohm resistors parallel to get ~770ma.



That's it!

Cool. :goodjob:
thanks

Thanks. But as far as I know the difficult part is to get the head opened without marring the finish.

Hmmm. Great thread. What would you need to get 500-550ma?

KDOG3 said:

Hmmm. Great thread. What would you need to get 500-550ma?

Click to expand...

:thinking:
This is a latest KL1 circuit. So it run about 500mA.

What is the best method for opening the head? I have a kl4 i want to swap leds on and i assume it will be a similar method.
Marc

I have no idea what the easiest way to get the head open. I recieved mine opened. It clearly took quite a bit of effort to open it, as the head is prett beat up.

It depends on how much threadlock there is. Try with your bare hands first, then with some type of rubbery substance, then strap wrenches, then try boiling and then strap wrenches, and if that doesn't work, bust out the locking pliers and something that isn't easily broken through.

ROK said:

:thinking:
This is a latest KL1 circuit. So it run about 500mA.

Click to expand...

Are you sure? That seems kinda high. I could swear I've seen something that said they run at 350mah.

KDOG3 said:

Are you sure? That seems kinda high. I could swear I've seen something that said they run at 350mah.

Click to expand...

I have measured forward current of new/old KL1 many times.
Only old KL1 shows around 350mA.

Nice thread :thumbsup:


What kind of resistor do i need to pump up the old KL1 with 350mA output?
To lets say 700+ mA

Are the shoppe resistors aprox the same size as these?

Benny

Benny, the resistors at the Shoppe are a whole lot smaller than the resistors on the KL1 driver. Wayne uses those little 0603 resistors on his drivers and they are really fun to piggy back solder. :shakehead I have done it quite a few times but...... SHEESH! :sweat:It has been a while since I was goofing around with my KL1 so let me rack my brain and see what info I have on it. I`ll let you know what I find or :thinking:.......... remember? :shakehead OK find!

Pheew,


Im glad i didnt press the buy button.

Need to get me some of those solderable resistors...

I sent CM a pm about this stuff .
Benny

MorpheusT1
The resistors are 1210 size I believe (still bl**dy small to solder). With the
Gen1 I think you need to change both the sense resistor 1R0 and the coil resistor R100 or R10 same thing. Stacking the same value in parallel will near double the current. I've just finished doing a Gen4 it only needs the sense resistor done but instead of stacking a 1ohm on top of the .68 resistor I just replaced it with .39
I have a trashed Gen1 circuit from taking apart a rather stubborn head. If you want I can send you the 2 resistors.

:twothumbs
Thanks for the offer,

So if i piggybaqck those two original resistors on top of the ones i already have output will double?

My head is a Gen1 KL1.


Benny

Yep that's correct. This only applies to the Gen1. The only thing to make sure is that you make good solder joints when you do it as we're talking very small resistance and a poor solder joint could up the resistance enough to cancel out any increase in current.

PM me your address if you want them. Sorry you'll have to supply your own magnifying glass!

Eryk

PM sent



Benny

Got your PM.
Will ship tomorrow. No charge.
Found this thread that I had bookmarked
https://www.candlepowerforums.com/threads/168616
Don't know about the coating as I always give anything I solder to a bit of a scrape and a swab with isopropyl.
I used to use a small dab of superglue to hold SMDs in place before soldering
but I made a simple jig that I now use.

:twothumbs

Thanks man,

I am very curious if can make this work

If not and my soldering messes things up i will put a DX 750-800mA board in there.


Thanks for the link too,lots of great info there.

PS: I just realized mine is a Gen2 head due to the crenulated bezel.1Gen was plain.
Same procedure on these?

Benny

Thanks for posting this guys !

Any ideas about KL4 circuits ?

Benny
Posted SMDs by airmail letter this morning should be arriving in your postbox in about 3 or 4 days.
As to yours being a Gen2 because the bezel was crenulated I don't thing you can go by this as the head my one came out of had the scallops/flats around the head in other words it looked like the latest Gen4 on the outside and it wasn't until I opened both up and saw the driver was different in each head.
If I remember the head that the Gen1 driver came out of started with A2.
I'm new to this surefire stuff and was calling it a Gen1 because the driver looked identical to the pics of the driver in the Gen1 head (the round one with rings around it)