Help from RPL owners....

Hi all, I got a question for any RPL owners, specifically the 425.

I am troubleshooting another members laser and am doing
some basic tests before I begin repair...

First noted, the current draw. From a cold start im seeing 790mA
which settles around 800mA.

The pump diode is outputting approx 1.4W, give or take,
I only did a quick test just to make sure it was up to par.


What id like to know is the 'average' current draw for the 425's
and the associated output in mW.


If anybody has graphed their 425 no matter how old, a screen shot
would also be useful.

I will post some pics at a later time showing the overhaul from
start to finish..


Thanks :beer:

I have an RPL 425 that gives 450mW's...

It is drawing 2.240 Amps at that power...

Thats what struck me as odd :thinking:

If this was in fact a 425, I expected to see a much higher
current draw.

Perhaps this was sold as a 425 but was in fact a 250 (if they make a 250..).

The LD appears to be functioning well, and is putting out a good solid
output. So either this is a lower output 532 or the driver is no good..

I'm still waiting to find the history of this laser, and if there was any
paperwork included. I don't want to move on until I have an idea of
whats in my hands first..


Thanks for the info :beer:

Mine goes right to max power from a cold start within 10 or 15 seconds...

I asked Jack to pick one for me with these characteristics...

Obviously, you have to have a battery that can handle that kind of current draw. Cheap 18650's won't cut it...

wannaburn said:

Thats what struck me as odd :thinking:

If this was in fact a 425, I expected to see a much higher
current draw.

Perhaps this was sold as a 425 but was in fact a 250 (if they make a 250..).

The LD appears to be functioning well, and is putting out a good solid
output. So either this is a lower output 532 or the driver is no good..

I'm still waiting to find the history of this laser, and if there was any
paperwork included. I don't want to move on until I have an idea of
whats in my hands first..


Thanks for the info :beer:

Click to expand...

For your information an RPL-165 and RPL-450 both use the n-light 2.5W diode and both draw the same current. The output depends 90% on crystal quality/purity.
Current draw is typically 2 amps with the non-adjust model and between 1.0 to 2A with the adjustable model depending on diode current setting.
If you're using an amp meter in series with the tailcap, then current will be less as you are modifying the circuit's impedance by a great percentage with the added impedance of the meter leads and the meter itself. The battery will make a difference as well as a protected 18650 will also increase the circuit impedance and decrease the current.

Thanks for the input guys...

Im going to re test it as is when my new LPM gets here... Mine has been under reporting
and its time for a tune up..

The battery im using is an unprotected panasonic cell from an unused dell laptop pack.
It doesnt appear to be as cheap as the ones I got from DX, but I will try a few
different batteries just in case.

Im using a 2W 1ohm between the battery and cap + DMM to measure
the current draw, but wont be messing with the LD... It was just
to see if there is an issue with the driver..

I figured id start with some baseline testing and go from there.

Is there a common issue with the 425's aside from LD related?
The head is well sealed and the laser was not dropped.
Yet if the head is tapped gently while on it appears to affect
the modes.

My thoughts so far is that either A-there is a simple alignment issue
that can be fixed with a steady hand, or B- a cracked or damaged
pump medium.


Any info on the pump medium? Im assuming nd:YV04 / KTP 2 pc
with HR & HT coatings?

The cap value is crucial for the driver. Only 0.4Ω or so will give you full power.