DHOM 532nm TEC setup appears to be totally Kaput!

[catalanjo]

Help needed desperately !

I have a problem with a recently purchased DHOM 532nm (model DHL-100A PSU, and model DHL-W532-1000mw head).

Power starts off nice and high and well over spec when first switched on but degenerates to less than half a watt within minutes.
If I switch off for a few minutes then switch back on the symptoms repeat themselves.

I can not detect any heating what so ever on the base of the head module so I assume that the peltier/s is/are not operating correctly.

Does anyone have a schematic for this laser since I need to know whether the problem is the temp sensor in the head, the peltier itself or the peltier driver.

I am loathe to take the head apart as dirt could possibly get in since I do not have a class A clean room or anything remotely similar so I would prefer to diagnose the fault from the PSU end of things for the time being.

I feel I have probably been sold a pup since I can not imagine how this type of fault could have possibly have developed during transport.

Does anyone have any thoughts on this ???.

Has anyone ever heard of a thermistor getting "bumped-off" or a TEC circuit giving up the ghost when obviously not powered up ?

The laser was switched on only ONCE for less than a minute using a 4.5volt battery as modulation input to check that it was lasing on arrival and then immediately replaced into its packaging before I got to test it properly with my Ophir power meter five weeks later.

I have already checked for any apparently loose wires and found none in either plug or socket on the PSU.

There is a fully populated 8pin socket on the PSU and a plug on the cable connecting the PSU to the head (which is hard wired into the head through sealed case holes). Since inside the PSU these eight wires split into four two pin connectors on the main controller board I assume the following in absence of further info:

Two of these are the fan supply the other six are probably 2 x pump input, 2 x peltier drive and 2x temp feedback suggesting that there might be only one peltier for the entire optics train!
Although ideally I would expect at least two peltiers, (one for pump and the other for the frequency doubler and stretcher crystals) and two temp feedback devices.

However despite the four way split in the PSU it is conceivable that there are common rails which would allow for another peltier drive and another temp feedback signal especially if the fan supply is shared with the pump input (very dubious but still possible). The internal PSU wiring design and the wire thicknesses (four thick and four thin however make all this somewhat unlikely).

Also since this laser is clearly of Chinese origin the design criteria is more likely to favour price and carefully selected crystals over thermal stability and linear modulation characteristics.

I am somewhat up shit creek without a paddle here !

Even the wiring diagram (or just the pin out) for the head to PSU connection would be a great help since this would enable me to monitor the peltier drive voltage/current and the temp feedback from the head so as to help diagnose the exact nature of the problem.

Does anyone know if DHOM lasers frequently suffer this type of fault ??

Who has repaired/stripped/rebuilt one of these babies?

Any info will be gratefully received either as a post or a PM.

Thanks!

Cheers

[laserdj]

I Have a DHOM 800mw 532 that starts fine then begins to fade... then some times it kicks back full power after a while, sometimes not. Seems we have the same problem, not a clue what it is...

[norty303]

If they were recently purchased, why don't you warranty return them?

I had a Laserwave green that was doing similar things, quite heat sensitive. Rob had a look and found the SHG wasn't well coupled to the cooling so it was over sensitive. He sorted it and its calmed right down now.


Also, have you tried contacting Marc or Shawn (iirc) to see if they can help with schematics, as they are the distributors (I think)

[300EVIL]

I'm not saying this will solve your problem but try warming the head with a hair dryer to about 85F while it's running and monitor output power. KTP does not like to lase when it's too cold. If your power output further degrades, its most likely a TEC fault as you pointed out.

[catalanjo]

Hi people, many thanks for the quick responses they help keep my spirits high, solidarity is a great feeling. It feels like I am getting somewhere albeit one minute step at a time.

Still searching for specific DHOM info !

@Evil
Thanks for suggestion Adam a bit rough but very simple and effective, and this, as you point out would at least confirm beyond doubt that it is a definitely a TEC problem not a stray ant or some weird "laser bug " LOL crawling around the optical cavity.

@Norty
No warranty I am afraid since I purchased it second hand albeit with excellent seller references from a PL member.
With regard to SHG thermal coupling, I find it difficult (though not totally impossible) to believe that transportation, in a well packed box, could influence this. This possibility would tend to confirm that the seller was aware of the problem and kept mum about it and I am trying to avoid this conclusion as much as possible until such time as a precise diagnostic becomes available.

Forgive my higorence .... but what does (iirc) mean exactly ?

Pointers to Marc (presumably = CT and Shaun = in Canada?) will probably be useful.
Thanks a bunch.
Rob would be a great solution but I am at present with the laser in Spain not UK, and also he is more LW than DHOM I think.

@laserdj
I think we may have similar problems, but by no means identical ones. Your problem sounds intermittent and unpredictable, mine in contrast occurs like clockwork every time. The only thing they have in common, is probably that both are cooling issues.
Once I have the info I need, I will endeavor to try and help you with your situation which sounds very embarrassing if you are doing gigs. Please do NOT sell this laser of yours without advising any prospective buyer of the problem,(for some poeple it is a small problem, for others it's gigantic and would be most dishonest although probably very easy to achieve).

Cheers

[buffo]

Hey Lari;

First: iirc = if I remember correctly (internet shorthand)

Second: I can vouch for the fact that the laser did not have this problem when I had a chance to test it (which was about 7-8 weeks before you bought it). I ran that laser for several hours at full power without any problems. (I also ran it for a couple hours under normal modulation, to be sure it didn't jellybean.)

That doesn't mean that a problem didn't develop during shipping, of course. I'm not doubting your report that it's got problems now. But I had originally intended to purchase it myself, which is why I tested it so thoroughly. I can promise you that Jeff did not knowingly sell you a defective laser. For one, he doesn't operate like that, and besides, I *know* that laser was working as advertized when I had it. Jeff didn't do anything more with it besides power it on shortly to take a couple pictures before he listed it here on PL.

Anyway, I just had a thought... That laser is probably still under warranty even though it was transferred to you. I know I was able to claim the warranty on my Lasever unit even though I wasn't the original buyer.

So before you open it up (possibly voiding the warranty), maybe you might be better off sending it back to China to get it repaired professionally... I think it's worth checking into anyway.

Have you contacted Jeff about it yet? (Do you want me to call him?)

Adam

[catalanjo]

Hey Lari;
Have you contacted Jeff about it yet? (Do you want me to call him?)
Adam

Hi Adam,
I had hoped to be a bit more discrete about this until I have a firm diagnosis.
No I haven't contacted him as yet since I prefer to have a recorded printout of the power output before doing so.
I am busy mounting a test rig right now as per my PM.
I will PM you as soon as I have results.
If there is any chance of a warranty YES please contact him for details.
I have only looked at the PSU plug so far so no seals broken until authorised to do so by Shaun or Marc.
Who was this laser originally purchased from ?
Thanks for the reassurance.

@laserdj
Have you talked to Shaun about your DHOM problem ?


Cheers

[catalanjo]

Hey Adam,
Regarding the fan noise :
http://www.photonlexicon.com/forums/...ght=ultralaser

Looks like my girlfriends little brother was not the only person to remark on this !

So I assume it to be normal for this beasty!

Cheers

[kecked]

I have 500mw and there is knee just like every dpss green out there. I run under the knee to avoid it and it is linear as a ruler. Mine works quite well. Contact Shawn and he will fix you up. ultralasers@gmail.com This is direct to Shawn.

[catalanjo]

I have 500mw and there is knee just like every dpss green out there. I run under the knee to avoid it and it is linear as a ruler. Mine works quite well. Contact Shawn and he will fix you up. ultralasers@gmail.com This is direct to Shawn.

Thanks for direct Shaun link (email I had for him was different and quite ancient) !

Unless I misunderstand you completely the "knee" in my case would be a maximum power that did not require TEC which in my case (since TEC clearly isn't functioning ) would be about 300mw so not very useful really!

But thanks for advice, I will "explore" the knee I think you refer to once I have the TEC sorted and post results on this thread.

Cheers