EastwardYJ U2 style w/ DX Q5 WG upgrade

I finally got more DX Q5 WG's the other day so I decided to put one in my EastwardYJ which had a P4 in it. This was an easy mod since you can remove the star by taking out 2 small screws and de-soldering it. There was no thermal paste so I added some with the Q5. So the results?

P4 was giving me a Vf of 3.33 and a LUX reading of 3,430 at 1 meter

Q5 is giving a Vf of 3.5 (Got lucky there), and a LUX reading of 4,900 at 1 meter!

I think the tint is nicer as well with the Q5 WG.

My LUX meter from DX seems to read very low. I may contact them to see if they would exchange/replace it.

Wade: How does it look to your eyes? I like my EastwardYJ, and am curious if you think the improvement was worth $10.

i did mine with a WC Q5 from cutter and the difference is pretty huge. although im just going by eyeball, it really seems much brighter.

The stars that cutter uses arent exactly the same as what was in my U2 clone and the screws that originally held down the star were too small for the notches on the new star, so i had to thermal epoxy it on instead.

Lighthouse one said:

Wade: How does it look to your eyes? I like my EastwardYJ, and am curious if you think the improvement was worth $10.

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It's always hard to judge the brightness by eye when you no longer have the original emitter installed to compare. I think it looks brighter, and I think the tint is closer to white, a little more blueish before.

It was worth $10 for me, but it's not a HUGE difference or anything.

From the lux numbers it was about a 40% gain. Not bad.

Now, it's also luck of the draw, if I got a Q5 with a Vf of 4volt or more it may have trouble running at full brightness with an 18650 unless the 18650 was fully charged and held a voltage over the Vf of the Q5. My Q5 appears to have a Vf of 3.5 if I was measuring it right, so it should run fine until the 18650 drops below 3.5v.

WadeF, did you measure the current at the tailcap before and after the upgrade? My stock light only measured around 440mA, which was well under the 1200mA spec.

Yenster said:

WadeF, did you measure the current at the tailcap before and after the upgrade? My stock light only measured around 440mA, which was well under the 1200mA spec.

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How do you go about doing that?

I just put the multi-meter's +/- leads on the +/- of the Q5 star and took a voltage reading. Not sure if that gives me the LED's Vf or not?

I have always liked my Eastward U2 style (YJ-18WA) and its successor (YJ-18WF). I tried this upgrade with a Q5 star from Kai in one YJ-18WA. Don't know the Vf, but it was noticeably LESS bright. I put the P4 back in the light. I have some Q2 stars on the way from DX and understand that they usually have a lower Vf. I plan to give them a try.

WadeF said:

How do you go about doing that?

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Just take off the tailcap and set the flashlight pointing down, leaving the battery inside. Set the multimeter to mA (to measure current) and be sure the positive lead is plugged into the dedicated terminal for current (may be marked by saying fused 10A max). Then just touch the negative lead to the battery negative, and touch the positive lead to the exposed alluminum rim of the flashlight. You will see the flashlight light up and you will then read the current on the multimeter.

Also, which model of the U2 clone do you have (YJ-18WA or YJ-18WF)? I have the YJ-18WA.

Thanks bspofford for noting the different models.

I have the YJ-18WA. There seems to be some kind of circuit or resistor in the tail switch? Clicking it goes from HIGH to LOW and then off. This seems to be controlled by the tail switch some how? I'll try taking a reading.

Okay, my multimeter says 10A Unfused and that gives a reading of .544 (544mA?), and the other one says 400mA max (fused I think) and that gives a reading around 312mA.

Should I be seeing around 1200mA? I thought that's what this light was advertised at. (Just saw you pointed that out as well. Does testing this way show the current the driver is sending to the LED?)

The Q5 is brighter (higher LUX reading) than the P4 that was in it before. Would I damage the YJ-18WA with RCR123's? I think it's 4.5V max?

WadeF said:

I have the YJ-18WA. There seems to be some kind of circuit or resistor in the tail switch? Clicking it goes from HIGH to LOW and then off. This seems to be controlled by the tail switch some how? I'll try taking a reading.

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Yes, there is a two-mode switch in the tailcap for the high and low. The low mode just uses a 3 ohm (measured) resistor. You can measure yours to see it you got a 3 ohm or 7 ohm resistor.

Thanks for the tip on how to take the current reading Yenster. I figured it was easy, just never did it before. I checked my Dereelight and on max it's pulling 1150mA.

WadeF said:

Okay, my multimeter says 10A Unfused and that gives a reading of .544 (544mA?), and the other one says 400mA max (fused I think) and that gives a reading around 312mA.

Should I be seeing around 1200mA? I thought that's what this light was advertised at. (Just saw you pointed that out as well. Does testing this way show the current the driver is sending to the LED?)

The Q5 is brighter (higher LUX reading) than the P4 that was in it before. Would I damage the YJ-18WA with RCR123's? I think it's 4.5V max?

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The reading with the '10A Unfused' is the one you need to always use...it's the unrestricted reading, so don't take these high current readings on the '400mA max' terminal.

So your light is just like mine...it doesn't meet the specs of 1200mA. Your reading of 0.544 (which is 544mA) means that's the current from the battery (not exactly to the LED), and depending on the charge state of you 18650 battery, it's around 4V. So, 0.544 times 4V equals 2.18 watts from the battery. That's the absolute maximum power going through the LED assuming 100% efficiency through the circuit...but it won't be 100% efficiency. It's will be close since the Vin is close to Vout.

I haven't tried the 2 x RCR123A since this light is suppose to be 1 x 18650 only. But the fact that this light has such a low Vout makes me wonder if maybe this is a 3.6 - 9V circuit (that's what I got in a WF-600 that should have been 18650 only). But I'm not going to try it.

If you're wanting to try modding the circuit in this light...
The solution, specifically for the Eastward YJ "U2 Style" light, is to get into the driver and short out the resistor at "R1". That will bring up the current from around 440mA to around 700 mA (in my light anyway). You will probably to very happy with this mode. However, if not, then go to the next level and direct drive the Q5 by moving "LED -" to "J1". This will result in around 950mA and you're bound to be happy with that brightness.

WadeF said:

Thanks for the tip on how to take the current reading Yenster. I figured it was easy, just never did it before. I checked my Dereelight and on max it's pulling 1150mA.

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Oh, remember to always unplug the positive lead from the '10A' terminal and put it back to the '400mA' terminal for measuring Ohms and Voltage. If you have a decent MDD, it will beep at you if you forget. Otherwise, you could blow something when measuring voltage.

Yenster said:

If you're wanting to try modding the circuit in this light...
The solution, specifically for the Eastward YJ "U2 Style" light, is to get into the driver and short out the resistor at "R1".

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How do you get at the driver? Unscrew the head from the body tube?

Oh yeah, that part is not quite as easy, but workable. The head has some kind of glue in the threads which can be broken when warm. I wrapped a rag around the body and then gripped it with a vise-grip. Then turn on the light on high for about 2 minutes where you can feel it get a little warm. Then I twisted the head off with my hand. There was just a little cracking noise but it really wasn't that bad.

Man you are lucky with your Q5, got mine today with forward voltage of [email protected]. Swapped it inside WF-400 and got dimmer :thumbsdow as the result so i put back the original Q2 that WF-400 came with.

How do you measure the Vf for a Q5 mounted on a star?

bspofford said:

How do you measure the Vf for a Q5 mounted on a star?

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Just use a DMM and touch the +lead to +LED, and touch -lead to -LED when there's power going to the star.

But let's make sure you understand the Vf concept (I appoligize if you already knew this, but I just wanted to be sure).

Vf is the front voltage that's required for a certain current, mA. And there isn't a single Vf, just like there isn't a single mA. When people talk about Vf, they are talking about the various voltages needed to drive the various currents through the LED.

So, I've seen questions like "What is the Vf rating for the Q5?" which is not a valid question. It would be like asking "What is the mA rating for the Q5?" which again is not really a valid question. So a valid question would be "What is the Vf required to drive a Q5 at 1000mA?"

So, the Vf and mA are dependant on each other and will vary on how you power the LED.

Here's a good recent thread with someone who measured the various Vf data points for the Q5.