PHR-803T new build..not lasing

I am reconstructing my old Blu-Ray laser with new parts and I am running into the issue of the diode going LED from the get-go. I have a new Microboost driver, new PHR-803 diode, and a new 14500 battery fully charged. The Microboost I got from Flaminpyro was set to 120mA and the diode from Modwerx. I used a static strap when handling and assembling the laser and soldered at the lowest setting. I am not a novice at soldering so I know that I didn't 'cook' the driver or diode when assembling.

After assembling and placing the diode/module/heatsink into the host, I added the battery and clicked the switch. Nothing but dim LED light. Several years ago I had built the same laser and it worked great for years until THAT diode went LED a couple months ago. I went ahead and got a new diode, driver, and battery just to cover my bases...now this new build is suffering the same problem. It is frustrating. From what I remembered on the last build, I soldered diode + to D+ per the Microboost manual, and diode -/ center pin to the (D-). I put a contact spring on the (+) on the power end of the driver and (-) is via the case.

I thought maybe something was wrong with the tailcap switch, so I pulled the whole module out, soldered leads to the power in, and tried powering directly off the battery....still LED.

Did I just get a crap diode? The driver looks fine, no solder bleeding to where it shouldn't. Any tests I should run?

Did you use a test load to verify your current? maybe the pot was bumped and went up in current?

Also did you short the output leads of the microboost before connecting them to the diode?

You may of damaged the driver because you wired the the diode up wrong (across the top pin Anode and the center pin), the driver would see that as an open circuit, meaning no current was flowing, so what the microboost will do is keep boosting the voltage until there is current flow, in doing that it can damage itself.

it should be wired up like so:



120mA is the absolute maximum for a PHR-803T diode, if you want it to live comfortably then set it between 90mA - 110mA.

Fiddy.

When using a MicroBoost driver, you cannot connect the diode the same way you would connect the diode to a MicroFlex.


+ driver output to diode anode
- driver output to diode cathode only

+ driver input to battery
- driver input to case/case pin

This is how I install the MicroBoost with a Violet diode.

I did not use a test load. I paid for a driver that was set to 120mA from a member of this forum, so I trusted his expertise. I was planning on a drop-in build in this instance. My last PHR-803T build used a Flexdrive v4 set to 120mA by DrLava himself and it worked right the first try and kept working without issues for 3 years until the diode LED'd on me. Instructions for my old build called for connecting the case pin to the negative output of the driver, I just assumed that the Microboost design required the same connection. I kept all the same parts (host, heatsink, Aixis module) and just pressed in the diode with a press tool, soldered diode to driver, soldered spring to positive driver input, dropped the works into the heatsink and host and fired it up thinking it would all work. I did not short anything out and I did not power up the driver "dry". I did not reverse polarity and I did not connect the case pin along with the anode, I connected the case pin with the cathode like I did previously back when I built the first laser in 2008. I double and triple checked with a magnifying glass to make sure traces were clean and nothing shorted against the heatsink or diode. I didn't realize that there was a difference between connecting the Flexdrive v4 and the newer Microboost driver to the PHR-803t. The diode is pressed into the Aixiz module which is then set into a conductive aluminum heatsink, so I assumed whether the pin is soldered down or not, it is still contacting negative through the case. Ground is ground right?

What WOULD make a difference is if INPUT NEGATIVE is isolated from OUTPUT NEGATIVE i.e. not sharing common ground. Is driver input negative not a shared common with driver output negative? If this is the case, then is it the driver or diode (or both?) that I just smoked money on?

if you read the microboost manual, it says

"Unlike many other drivers, the battery negative (-) connection and the diode – (cathode) connections are NOT
continuous. As such, the diode anode and cathode must be electrically isolated from the laser casing, if the casing is
connected to a battery terminal. Most Blu-Ray 405nm diodes are constructed with an anode and cathode electrically
isolated from the casing, so no extra isolation is needed"

Well, there is your problem, you used case pin as negative when it is not. Hope you didn't clip the third (true negative) pin!

Sigurthr said:

Well, there is your problem, you used case pin as negative when it is not. Hope you didn't clip the third (true negative) pin!

Click to expand...

No I didn't. I bent the case pin down to meet the negative pin and soldered both to the D- driver output pad...just like I did on the older first build. I of course did not read the Microboost manual thoroughly.

I guess the damage was done because even lifting the case pin from the circuit did nothing to make the diode lase. It just emitted dim purple light.

My next question is did this toast the driver or just gank the diode only?

I can't say for sure since I've never used that driver, but I would bet that the driver is toast but the diode may have survived. If you've got an LM317 handy just rig up a test driver to check the diode, if it works you know only your driver is dead.

use a test load to test the driver!

Mmm nope, no LM317 handy, no test load either. Both necessities I will be getting soon. Bit by not RTFM. Assumptions are the mother of all f***ups.

I just did this same thing with a 450nm build Here is a pic of what the wireing should look like to a microboost driver. Notice the bat- on the microboost is wired to the casepin on the diode. The rest is just standard wireing.