Malkoff MD4 Wildcat

Candle Power Flashlight Forum

Help Support CPF:

The flicker is more likely the result of being right on the hairy edge of regulation. Where it is coming in and out of regulation and has a positive feedback because of it. The voltage drops because of the resitor limits the load, the current goes down, the voltage comes up slightly under the reduced load, its just enough to start into the edge of the regulation, draws more current but can't sustain it so it drops the voltage again,and the cycle continues. I have seen this before.

the best way to prove this is to have the batteries sag some more under higher power use and do this again and see if it goes away. There should be less and less of this flicker as the battery voltage sags because they are being run down. If its got PWM it would continue to get worse as the batteries sag.
 
I've done a bit of investigation and the strobing effect seems to be there all the time at all states of charge although it doesn't seem to get any worse or better as the batteries deplete. The only battery configuration where you can't really notice it is freshly charged cr123 cells. As they start to run down, the flicker becomes noticeable. It's even there on 1 x 18500 where I'm getting a current of ~10mA.

Is it possible that they replaced the resistor with a PWM circuit for greater efficiency? I've done some efficiency approximations using current, voltage and ceiling bounce tests and I reckon the efficiency is almost as good as, if not as good as my Fenix TK11 R2 on low. I wouldn't expect it to be that good for resistor drive.
 
monkeyboy said:
I've done a bit of investigation and the strobing effect seems to be there all the time at all states of charge although it doesn't seem to get any worse or better as the batteries deplete. The only battery configuration where you can't really notice it is freshly charged cr123 cells. As they start to run down, the flicker becomes noticeable. It's even there on 1 x 18500 where I'm getting a current of ~10mA.

Is it possible that they replaced the resistor with a PWM circuit for greater efficiency? I've done some efficiency approximations using current, voltage and ceiling bounce tests and I reckon the efficiency is almost as good as, if not as good as my Fenix TK11 R2 on low. I wouldn't expect it to be that good for resistor drive.
Click to expand...

This is a completely new driver since the 3 LEDs are in series and not parallel, so its possible it does have PWM to boost up the voltage and doesn't use just a resistor to provide the lower power mode as before.
 
PoliceScannerMan said:
Can anyone confirm this?
Click to expand...


This information came directly from Gene, the 3 LEDs of the new Wildcat are in series and has a boost driver. Whether or not it has PWM I don't know I never thought to ask at the time. From the test results shown, it appears to be for low mode.
 
How is low mode accessed with MD3 Wildcat? Previous MD4 used the resistor ring, and low was accessed by unscrewing head slightly?

Bill
 
Not sure what the old one was like but this is a picture of the new one:

malkoffhead.jpg


When the head is loose, theres a spring loaded pin that makes contact for low and when the head is tight, the whole ring makes contact.
 
monkeyboy said:
Not sure what the old one was like but this is a picture of the new one:

malkoffhead.jpg


When the head is loose, theres a spring loaded pin that makes contact for low and when the head is tight, the whole ring makes contact.
Click to expand...

That's a resistor ring. Unscrew it and you should see the resistor on the other side. Do not know what is causing the flickering. Maybe the value of the resistor could be changed to allow more current to flow to the LED, though that is just a guess.

Bill
 
I won't unscrew it just in case I break a wire or something but those are just electrical contacts that could be connected to anything, be that a resistor or a PWM circuit.
 
monkeyboy said:
I won't unscrew it just in case I break a wire or something but those are just electrical contacts that could be connected to anything, be that a resistor or a PWM circuit.
Click to expand...

Looks to me that the ring was screwed in as final assembly, so there would be nothing to break. The description for the MD3 head on Gene's site, notes that the output on low will depend on the batteries used. If there was PWM used for low then the low mode would be regulated, and size of batteries used would not make a difference, except that proper voltage should be used for regulation. I understand your reason to not want to remove the ring, in that it comes integral with the head, and is not an add on like the MD2 resistor ring.

Bill
 
MrGman said:
This information came directly from Gene, the 3 LEDs of the new Wildcat are in series and has a boost driver. Whether or not it has PWM I don't know I never thought to ask at the time. From the test results shown, it appears to be for low mode.
Click to expand...

Fascinating (to this non-tech). Is that uncommon (running the LEDs in series)?
 
I didn't realise that the old Wildcat was in parallel. Series is generally better as the current through all of the LEDs is matched so you don't get e.g. one led with lower Vf driven harder than the rest.

I'm really not sure whether or not it uses a resistor anymore. It could very well be. I'm comparing the low level efficiency to my TK11 in kind of an unscientific way as I don't have a lumensphere. But my general feeling now is that the TK11 is a bit more efficient on low than the wildcat on low maybe only 10-20% more which in real terms is nothing. I'm not sure how much efficiency you would lose with resistor drive.

Another thing I've noticed is that the low output is a little unstable due to that tiny pin contact. It tends to flicker slightly when the head is touched. This could be remedied with a stiffer spring behind the pin.

All in all though, this is an excellent light and I would still recommend it over anything else in the same category.
 
At this point, I would get a hold of & use some deoxit on the threads to make sure you are getting optimum electrical contact.
 
It uses a resistor for low. I've never noticed any flicker on my personal Wildcats with the same setup. Is anyone else noticing flicker?

Thanks, Gene
 
You must log in or register to reply here.

Latest posts

Back
Top