Mag Switch Resistance Fix.. 1/6th stock!

andrewwynn

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Ok.. too busy with a bazillion things to get to this sooner but here goes..

The step-by-step pictures are here

some highlights..

Image-CC3C364A5D3C11DA.jpg-thumb_202_269.jpg

new ground wire.. bypassing the sliding contact.. Important note.. the little circular ring.. now i actually make a whole loop back to itself and solder so there are doubled-up wires coming off.. 1/2 the resistance and double the strength.. it is absolutely necessary for that to be soldered back to itself so it does not separate when tightening the screw.. or the wheel will no longer roll.

I recently measured an old magswitch to have 18 to 100 ohms.. not miliohms.. OHMS!.. and as a testimony to Pro-Gold.. i put in 2 drops and worked it in and got it down to 6 or 8 miliohms in 20 seconds! nonetheless.. since it is the main part that fails.. i shorted it out with a wire!.. i actually cut out the slider so it can't short out with the new insides.

(resistance is now 1.43 miliohm)... typically it is 7 to 15.. not terrible actually... just when it gets dirty it's the biggest problem.

Image-CC3CE42B5D3C11DA.jpg-thumb_269_202.jpg

hardwire the switch.. drops about 10-20miliohms.

Image-CC3BDFBE5D3C11DA.jpg-thumb_269_202.jpg

solder wick through the spring.

This is by far the biggest improvement.. typically that will measure on the order of 100-120 miliohms.. in-fact.. the 160+miliohm resistance will drop to 80 (half) by ONLY soldering the ends of the spring.. and still using the spring vs the solderwick.

this solution shown here drops the resistance of the spring to about 3-4miliohm and the whole ckt from the pos. terminal on the PR adapter in this case to about 12 miliohm.

I made a small change since this picture was taken.. i no longer bother to attach the wire to the bottom.. it comes out a hole on the side at the bottom and is attached to a wire that goes directly to the top contact on the switch.

Unfortunately i don't have any pictures yet of the battery spring.. but the wire goes through a hole drilled straight through the plastic to the bottom.. a notch is cut in the inner circle and the last 1/2 inch of wire is stripped and the end soldered to the edge of the top of the spring (so that it doesn't interfere with the spring's ability to be pressed all the way down).

The end result.. the switch i started with measured 500mV drop at 3A.. or 167mohm... after i was done with the modification.. it measured 27.3 mohm.

That puts it in league with the KIU socket kit. most of that resistance is where the spring contact touches the bottom of the PR bulb or adapter.. tough to get around that one.. but even the KIU socket i measured 7mohm between both contacts... this pr adapter to bi-pin i measured 3mohm per contact.. on-par with the KIU.. so since there is probably about 1-2mohm of wire, and 12mohm in the wire and contact.. that means 12-2-3 = 7mohm contact on the bottom of the bulb adapter.. that's as good as the best i've gotten a magswitch with progold (just the contact of the switch).. each contact outside the switch is another full 'contact' which will be about another 7-10mohm typically... and not trustworthy.

So.. the final results..

167mohm turns to 28.. 1/6th the resistance!

so a couple examples of 'the difference' using the fixed switch or stock:
1160 on 6V bat.. 5.39 to bulb.. 424/275 L > 5.89V 577/375
1111 on 7.2V bat.. 6.6 to bulb.. 649/722 L > 7.09V 834/542
1331 on 10.8V bat.. 10.46 to bulb.. 720/468 L > 10.74V 790/514
1185 on 10.8V bat.. 10.25 to bulb.. 1026/667 L > 10.7V 1194/776

and my favorite comparison.. a lesson in power transmission.. why does the power company use super high voltage to transmit power.. here is why:

1323 on 14.4V bat.. 14.21V to bulb.. 414/269 L > 14.37V 430/280
(that is 15.6 vs 15.9W)
1183 on 4.8V bat.. 4.19V to bulb.. 274/178 L > 4.68V 406/264
(that is 15.1 vs 18.0).

so.. barely a difference in output with the high voltage low current solution... but in the low voltage solution... there is a 40% drop in output with the stock switch!

Well there you have it.. look at the bulb options and see if you are in there.. think about it.. it is CURRENT that causes the voltage drop.. so if you have a bulb with low current you'll be less affected.. this means that the 1060 and the 1185 and the 1183 will be most affected..

You may have noticed the omission of the 1166.. it's because it's a sucky solution for direct-drive.. that bulb is underdriven a lot from a 10.8V solution.. enough that there is only a 30 L swing in the output... now that is absolutely a fantastic lamp when pushed properly to 12.5V or so.. 900/600L.. My little 1D FM light is outputting 900/600L for 20 minutes on a charge .. and it takes a cent to charge.. probably not even.. so 3 cents/hr compared to the $8 to $100/hr with the M6.

I hope this helps people.. it is not a terribly difficult mod to undertake.. you just need solderwick, some regular wire (extra flexible type is good.. i used 14ga speaker wire.. and some 18ga wire (which is fine.. 18ga is 1 miliohm per two inches!).. you need a drill, some cutters and of course a 5/64th screw.

Oh.. very helpful tip.. to solder to the cups.. it's pretty tricky usually.. it can be done with a higher watt solder iron or gun.. but by far the easiest is to hold the cup concave side up... in the likes of the holder shown.. and heat the bottom with a micro blowtorch.. puddle some solder into the cup (careful.. you'll likely start some rosin on fire).. and then touch the solder wick into the puddle of solder.. then put down the flame and use a heat-sink to cool the cup.. else it takes like 10-15 seconds for the solder to solidify.

if you only solder across the spring and do no other mod.. well .. put some contact cleaner on the slide while it's apart.. you will drop the resistance to about 60mohm.. and that will have this level of result:

1111 on 7.2V.. 6.6V to bulb 649/422 L > 6.98V 790/514.. comparing to: 7.09V 834/542 if you 'go all the way'

So.. just fixing the spring will gain you 141L and shorting out all the contacts also will get you 185L gain.. however..that means a 22% vs a 29% gain, so balance how much it's worth in deciding what to fix.

order of importance:

spring spring spring.. over half the resistance
sliding contact... good initial resistance.. TERRIBLE long-term.
outer switch contacts.

There is a weird thing about how the magswitch is designed.. it is specifically designed to be cheap to assemble and reliable (i'm talking about the electrical switch not the whole assembly).. but at a serious penalty to the electrical resistance.. here is why...

as anybody that knows ohms law knows.. series resistances add up...

ANY and EVERY time.. you have a 'contact' you are going to have SOME resistance.. and typically even the very best contacts are between 5 and 10 miliohms.. The problem with the design of the switch is this..

Rather than having a hard-wired single SPST switch which could be 5 or 8 miliohms... There are FOUR series switches in a mag switch..

(1) contact from + spring pad to switch lower contact
(2) switch lower contact to connecting donut
(3) connecting donut to upper contact
(4) upper contact to PR holder spring contact.

2 and 3 are exceptionally low resistance.. 4mohm if you treat them.. more like 6 if you don't.. but 1 and 4 are iffy.. 10 to 15mohm is not unlikely..
that means.. rather than 5 or 8 mohm.. the mag switch stock is more likely 30mohm to 40 mohm.. easy enough to fix with hard-wiring the troublesome contacts and get it down to 10 or so.

Hope people can follow and it helps!

-awr
 

IsaacHayes

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Hehehe good job. I've thought of similar idea, but I don't have incandecents (which your mod would make most sense). All my mags are luxeon, with a wire soldered directly from the switch to the led/driver.

Only points I could improve from what you showed was the battery spring + to switch +, and the switch with that pro-gold.

The C mag has a much different switch too, the D the contact points are much smaller. I would think the C could handle more current and possibly have less resistance? Any thoughts on that?
 
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andrewwynn

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I have heard the C switch is better constructed.. haven't taken one apart yet.

I don't have my RT4 switch modified.. it surely drops some power but the regulator is downstream so it only hurts runtime, not output. The battery spring to switch is hard wired... and the switch donut is treated with PG100 of course.. measured a drop from 12 to 8mohm.

-awr
 

redbird

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I have studied the PRSwitchFix on your web site and read and reread this tread over and over to try to get a better idea on how to do this. On your site you dont show the spring cups drilled out.

Which method is the best to use? What size hole and where does the wire go next?

I ordered a few switches to experiment with so your input would be appreciated.
 

andrewwynn

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the spring cups aren't drilled, just soldered to..

Image-CC3D67DD5D3C11DA.jpg


This picture shows how i attached the positive wire to the bottom of the spring. The wire on the right is soldered to the wire near the bottom of the spring. The ground wire is not as important.. by far the most resistance is in the spring and connections.. about 80+mohms..

I solder the solder wick inside the cups to the spring top and bottom, and then soldered another wire to the bottom of the spring through the hole that comes out the bottom (black n white wire in the picture) .. that wires goes around to the top of the switch and is hard-wired to the top contact of the switch (it's actually first attached to the switch for easy of assembly)

only soldering the spring and nothing else will HALVE the resistance from like 160 to 80 mohm. additionally fixing the ground will get you near 50 mohm.. going overboard and hard wiring the ground and the positive will get you near 30-40 mohm.

-awr
 

redbird

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Ok. That is clearer now. I see the hole you drilled on the pics on your web site but it was not clear to me from the notes and pics on your site.

This will help!
 

45/70

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Hey, awr,

Is there any way to incorporate your soft start idea into this switch mod? I Have a ROP with the modded switch. It would be really cool if the soft start could just be added into the wiring, retaining the PR base etc. Obviously, I'm not an EE. Soldering, yes. Electronic circuit design, no. :)

I have asked elsewhere if a ROP would actually benifit from your Hotdriver. Nobody really said. I'm sure it would but, it seems to me that the best part would be the soft start. It would extend the already, OK, bulb life. The rest of your hotdriver would seem to be overkill on a ROP. Thoughts?

Dave
 

andrewwynn

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I designed a soft-start circuit that wquiles bench-tested for me.. http://softstart.rouse.com

It could be made small enough to easily be incorporated into the PR fix.. the combo for many light options (like 1185) would be far less expensive than going the KIU socket and hotdriver solution.

example of improvement:

[email protected] host: 471L before, 535 after.
[email protected] host: 662L before 777 after.
[email protected] host: 175L before 258 after. (holy cow! 47% brighter!) just from some wires and solder, no other change!

I want to work out a ludicrously simple regulator that people can build for $5 so they don't have to spend $35 on my hotdriver... the design is already made, i don't have time to build a prototype though.

-awr
 

benighted

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I know this is an old thread but... I opened up my 6-C ROP to find that the switch style is different now. It looks like m@g did away with the double-capped spring and soldered a new style spring directly to the contact.

Has anyone else noticed this?
 

andrewwynn

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interesting for sure.. the spring is the most of the resistance though.. when the caps are removed from the equation on a D size mag.. the resistance will go from about 80 miliohms vs 180mohm.

-awr
 

Northern Lights

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It takes some manipulation but I have been soldering the braid inside the spring to the bottom of socket and taking the braid through the spring and soldering it to the postitive contact so that there is no friction contacts whatsoever. I have burned my fingers a few times doing it. I notch the bottom of the slug or put a small hole into it and solder the ground to it. I notch the bottom of the cam wheel channel to accomodate the ground wire. The rest is pretty much the same. On the Mag Charger the pedistal is all metal so grounding is easier but the process is the same for the slug.
 

Northern Lights

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Well, I just had a failure of the ground wire from the slug and I now have a new method of attaching the ground. I do not like making a small loop to be put under the cam screw, too difficult to make, too fragile.
I had been drilling a small hole below the cam screw next to the rim. I also extend the notch of the pedestal down to the switch to accomodate the ground wire. The mag charger slugs I have done are not steel but are an alloy and will take solder. The PR slug is not steel and does not solder well.
On this PR slug that lost the ground wire I put a small soft alloy screw into the hole and made a rivet out of it, pounded it tight and soldered to it. Then I realized that I can drill the hole partially through and braze a spot of brass to it and solder to the brass. Next one I mod or repair will go this route!
Edit:
OH NO! Don't do this, it is a brass alloy after all and plated. But I removed the plating by torching it then polished the now unplated brass PR slug and put a small hold in the base, this time it soldered well. The plating must have had an adverse effect to taking solder even when penetrated by drilling down to the base metal but adjacent to the solder joint.
 
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LuxLuthor

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I think I have read this thread at least a dozen times, and learn something new every time.

In many ways, I miss the educational posts from AWR.
 

vhyper007

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hello,
lemme see if i get this straight. simply changing the switch in a mag in the way you described ups the output by diminishing the resistance???

Since I can't solder, this is purely moot since I can't perform this mod but am I on target?

If so, why doesn't someone offer the service where they (for $$) will make this mod and sell it to dufuses who can then drop it into their mags which are now reinvigorated mags.

Call them ViMagras coz they get the output way up for just a little pill of solder.

Seriously,
vhyper007
 

mudman cj

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You got it - lower resistance means more voltage at the bulb for brighter and whiter light. This is more effective when running bulbs that draw higher current, and I wouldn't bother for a stock Mag bulb.

If you ask nicely in the custom/modified forum, I'll bet someone would be willing to mod your switch for you and send it back free of charge or maybe if you cover shipping.
 

eyeeatingfish

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I dont really understand where all the wires are going from and too. I understand the wire that went inside the one spring though. About that though, why is there so much wire (why not shorter?) and why did it have to be counterclockwise?

As for the rest of the wires, i guess ill have to take that piece of my mag out so i can get a better understanding of the system than jsut pictures can provide.
 

LuxLuthor

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I dont really understand where all the wires are going from and too. I understand the wire that went inside the one spring though. About that though, why is there so much wire (why not shorter?) and why did it have to be counterclockwise?

As for the rest of the wires, i guess ill have to take that piece of my mag out so i can get a better understanding of the system than jsut pictures can provide.

Check additional pictures here.
 

eyeeatingfish

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I saw the pictures, i think i will just need to see the actual piece in 3D myself to unaderstand it better.
Why is the wire in the spring coiled, and why does it have to go counter clockwise?
 
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