is my 300 mw blue labby DOA?

[Docjohn]

Fuzcub:

Another question. Is the place marked CUR on the above pictorial where you put the ammeter across?

John

[stanwax]

So you think I should connect 12v- and 5v+ together external to the PCB? I don't see any separate 5v- supply. I don't see a split rail here. Am I wrong?

Connecting the power supplies as indicated will create a split rail supply. The labels marked on a PSU are all relative. When you are measuring you need to know where the ground is (zero volts) and measurements are taken relative to this. By connecting the +5v to the negative of the 12v supply you are referencing them to a zero volts point. The place where the 2 join becomes this zero volts measuring point. All the +5v label means is that that pin is 5V positive in respect of the other connection so it follows that calling the +5v the zero volt point the other connection will be 5volts below this = -5V
And yes I would say CUR is to monitor the diode current and will be connected directly across the diode balast resistor. Check the value of the resistor - big white ceramic one - its likeley to be 0.1 ohm - if it is then you can read mV off your meter and convert to Amps by multiplying the reading by 10. So 0.45V across the res will be 4.5 Amps.

Rob

[MechEng3]

Crystals Length
(mm)
Deff
(pm/V)
Walk-off
(mrad)
Output Power(W)
Conversion Efficiency

BIBO
10.4
3.3
40.7
2.8
63%

LBO
0.81
11.3
1.52
33%

BBO 8
2.0
60.3
2.1
47%

Probably a 15 watt diode based on my personal notes....I would expect to see at least close to 20 amps at full modulation ........looks like it is in "park"......idle current just below threshold.

[Docjohn]

Ok here goes:

Resistance across large white ceramic resistor=4.8 ohms. Across CUR =4.76K either way. Heat sink of driver gets warm slowly. Heat sink of laser head gets hot fairly fast. (neither have additional sinking, but I only leave voltages on for short time and monitor temps very closly)

-12v,+5v, and -5v mod all connected together as a ground now. 3 bench supplies connected properly to 12v,5v, and mod input.

12v supply is set at 12volts and draws about 1 to 4 amps (it varies as things warm up) Probably the TEC feedback working.

5v mod input is drawing about 1ma from 0-5v. No change as modulation changed.

The 5v supply is the strange one. As I increase the voltage from zero up there is no current draw until about 1.9v, then current draw rapidly goes up until it maxs at 8 amps. The supply is then putting out 3.1v and wont go any higher no matter how high I turn the voltage knob up. So the load on that supply draws 8amps max, and wont let the voltage go any higher than 3.1 volts although the supply is capable of 20 v. at 40amps (reminds me somewhat of a zener diode across the supply). Switching the supply I am using to supply 5v with the one I am using to supply 12v makes no difference. (They both are variable voltage and rated at 40 amps) The mod power supply is rated at 1.5 amps.

No lasing observed at any time. The driver board sink and head sink heat up.

Basically hooking -12v to +5v and -mod all together made no difference in anything.

The material from Kyle doesn't show the schematic of the driver or head.

The activity of the supply going to the 5v input of the driver is what puzzles me

Why is the supply to the 5v input of the board only drawing 8amps and the voltage at the board input is 3.1v and wont go higher?

Any ideas or other things to try, measure, or do?

John

[Zoof]

Why is the supply to the 5v input of the board only drawing 8amps and the voltage at the board input is 3.1v and wont go higher?

John,

I have no idea if this applies to your situation, but it sounds like the PSU may be shorted so I thought of something I learned when hooking 2 PC PSUs in series to give +12V and -12V at 5AMPS.

In the PC supplies I had the secondary GND was connected to the primary GND. When hooking them up in series that connection should be broken. I broke that connection in both PSUs, maybe one would have been sufficient.

good luck finding the solution and thanks for the pics

[stanwax]

OK MAybe I didnt look close enough - there is no way that ceramic resistor is the diode balast resistor. If we say the didoe current was 5A (i know it isnt but bear with me) then you would need 23.5V across the 4.7ohm resistor to pull that current - add to this the 2v or so of the diode and you will need a supply voltage of 25.5V. Clearly this is wrong.
Check the markings of R72 attached to the heatsink - this is more likly to be the diode ballast if its in the order of a fraction of an ohm.
If we assume 5A again but substitute the 4R7 res. with a 0R1 then we only need 0.5v across the resitor so 2.5v in total - The supply will need to be more than this as there will be a transistor in there too that will drop the rest of the volts.
Hope this makes sense though it dont help with teh predicament

Have you a photo of the setup which clearly shows how you have it all connected?

Rob

[Docjohn]

John,

I have no idea if this applies to your situation, but it sounds like the PSU may be shorted so I thought of something I learned when hooking 2 PC PSUs in series to give +12V and -12V at 5AMPS.

In the PC supplies I had the secondary GND was connected to the primary GND. When hooking them up in series that connection should be broken. I broke that connection in both PSUs, maybe one would have been sufficient.

good luck finding the solution and thanks for the pics

Zoof:

I understand the basic concept of ground, but I don't understand the difference between primary and secondary ground.

Thanks

John

[Docjohn]

Have you a photo of the setup which clearly shows how you have it all connected?

Rob

A photo may be kind of confusing. There are wires everywhere with the 3 bench supplies and split rail wires throwen in there.

Do you think a pictural drawing would be better?

I can do either.


John

[thesk8nmidget]

all so confusing! i would say take a picture of your layout and then label the picture with some words so we can kinda figure out and make sure what everything is

[stanwax]

I understand the basic concept of ground, but I don't understand the difference between primary and secondary ground.

John
What zoof is refering to is simply the ground on the mains side (primary) and the ground on the low volts side (secondry) if they are tied together its could mess things up - This was refered to previously as 'floating ground' it simply means there is no direct connection between the grounds on the high volt and low volt sides of the PSU ie high volts and low volts sides are fully isolated.

Look at the image I have attached. A few years ago I used 2 laptop powersupplies to drive some G120 Scanners. I needed an split supply of 18-20V. I wired the 2 PSUs up as shown but as the negative of each supply was interternally connected to earth I had to break this connection in the one that became the -19V supply. Without doing this its output would have been dead shorted. Note how I have labeled the outputs as I expalined earlier to make them meaningful relative to the 0V line

And I agree with Josh a photo with notation would be best

Rob