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Meanwhile back at the Ranchco John-O.... Dead Dot? NO! NO you're not allowed to die!

May 26 2017 at 2:27 PM

John in FL.  (Login gratewhitehuntr)
AR&P



Weaver micro-dot, paid $30 used, 2 years + of great performance including a stint on the Hatsan 135 hard-kicker.
It ended up on the x60 plinker, handed around endlessly and left on for days, the small size makes single loading so much smoother than a scope covering the breach area.

Last week it got stuck ON and I figured the batt had dropped below minV to operate the board control IC.
New battery didn't fix it..... aw crap it's already broke....take it apart!
photo SAM_2085_zpst63caxo9.jpg



AH HA!!!
photo SAM_2086_zpsgvvmtil9.jpg

Too much heat will cook the switch, turned it down to 650-ish.
Chisel tip CLEAN AND SHARP!

I use a nail file to sharpen, and rubbing on newspaper or wet cloth will give you a clean shiny tip.
Soldering on newspaper helps control lead contamination of work areas.
photo SAM_2091_zpsorv0ncd9.jpg
photo SAM_2090_zpsxppamvad.jpg

Tinyyyyyyyy bit of new solder and I got most of the flux cooked/wiped off onto the paper then turned it down EVEN MORE till the filler would barely stay molten.
I really don't wanna booger this switch up with a lot of heat OR WORSE YET JOINING HALF THE BOARD WITH A GIANT GLOB!
photo SAM_2087_zpsdyxwm8lb.jpg

I stayed off the switch, trying to just catch the porous tips of the legs, but I'm not happy here.
It'll get broke again.... NEEDS MORE HEAT!
photo SAM_2094_zps17ye83lq.jpg

Plastic shows a touch of heat distortion, but the flow is great!
photo SAM_2101_zps1fpkvq55.jpg

WINNING!!!!!!!
photo SAM_2104_zpsbjukxdpp.jpg

Love the low profile of this dot.
photo SAM_2106_zpsemjejzho.jpg




    
This message has been edited by gratewhitehuntr on May 26, 2017 3:07 PM


 
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Garry Teeple
(Login Teep)
YF

Re: Meanwhile back at the Ranchco John-O.... Dead Dot? NO! NO you're not allowed to die!

May 26 2017, 3:24 PM 

I had an issue with one of my Bushnell Trophy red dots the other day when the knob locked in the off position. Took just a few minutes to take it a part, find the issue, correct it (probably only temporarily until the spring breaks completely), and put it back together. I have a love hate relationship with red dot sights. Love how they work in low light and on handguns but hate the constant on and off plus power adjusting and then there is the issue of leaving them on to find the battery dead the next time I want to use it. I did put a Vortex Venom on a .357 Magnum as it will not see a lot of use and will turn itself off if left on. My airguns get to much use so I'm either going to have to get more batteries or a better memory, let me know if you hear of a sale on better memory.

 
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John in FL.
(Login gratewhitehuntr)
AR&P

Dollar Tree sells 4x2032 for $1. I never looked close at guts, but I'll bet there are

May 26 2017, 3:55 PM 

a couple different ways to adjust brightness.
This unit uses a PWM to adjust brightnes and EEPROM to save brightness settings (there is your memory) The switch is a momentary, normally open.
Even when the switch came loose and couldn't be shut off it ran for a whole week on the original 2+ year old battery!
I took this as an omen that many squirrels must die....

Another dot with the turret/batt holder/switch/brightness 1-11 switch WILL be dead by morning.... brightness must be controlled by something which dissipates current.
I'll definitely stay away from that switch configuration from now on, unless they advertise uber runtime.

I don't know about brands, just bought this from a pawn shop on a whim.
Too many guns, not enough optics!


    
This message has been edited by gratewhitehuntr on May 26, 2017 6:00 PM


 
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Garry Teeple
(Login Teep)
YF

Brightness control

May 26 2017, 10:47 PM 

I wish I had looked a little closer at the 0-11 brightness control when I had it apart. I assume that the LED must maintain the same voltage to operate so some how current must be shunted off to dim the LED. If it fails again I will totally strip it and see what is going on. My electronics education was back in the late 60, and mostly tubes at that, so I might not understand it anyway.

 
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John in FL.
(Login gratewhitehuntr)
AR&P

I have tubes but no education, nobody has board space anymore! SMD is all so tiny.

May 26 2017, 11:42 PM 

The led flashlights all have fingernail sized SMD boards like these, I ruined more than a few with the iron! 20mm is cake after the stupid 14mm in AA flashlights and if it hadn't been a simple fix I'd have tried a whole board swap.
I have some 2 mode Hi/Lo boards, though they'd need some reduction of current.

PWM is a high speed switch with variable ON/OFF ratios that the eye sees as reduced brightness, the load sees as reduced voltage.
Of course on the dim settings it's mostly off and that makes the PWM efficient and versatile, and solid state wink.gif

Some drivers incorporate a 3 leg voltage regulator (like LM78xx), using led VF to control current. Multiples can be paralleled on the board for increased current.

There are also constant current drivers.... but I don't actually know how they work.

Led are very sensitive to voltage changes, the characteristic VF defines this sensitivity, with the entire current handling range sometimes occurring within +/- 0.2vdc
VF varies somewhat even throughout the same binning, so there are no absolutes, but it has been my impression that newer led have lower VF and they are still getting lower.


One Cree I set up on voltage variable driver behaved like 150ma@3.2vdc 1200ma@3.4vdc
An older bin wouldn't even turn on @3.2vdc was closer to 400ma@3.4vdc.
Of course that is a completely different class of led, just offering examples.


Crap, now I want to take apart the 1-11 unit....I wouldn't put it past them to have wipers on a resistor like some $0.18 pot....



    
This message has been edited by gratewhitehuntr on May 27, 2017 1:12 AM


 
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