LASER PROJECTOR trouble shoot/repair 101

I am not currently home- this PC does not have all I want to put into this thread...

I am sure many more than just me have a low cost PJ that has some kind of issue-the purpose of this thread is to get started on trouble shooting two LASERKING LK PD2s one does nothing (owned by George aka LaserFace) and the other (now mine as I traded with JamesCranmer) which has a dimming green module(it has been replaced which means the issue is not what we first thought)

IF we are very sure what part or parts are bad we can get free replacements from Linna- as its far better to avoid the very expensive cost to pay the shipping to and from China for warranty work- so I hope this will become a win/win/win.

Most who own one of these will agree that the low pricetag that comes with these laser projectors means that it may eventually need repair- its the trade-off we accept.
so please sub this thread and come back once I load the pics --

hak

I encourage any with help to chime in-- I admit I know very little about fixing PJs -so please bear with me--

Okay
First off-- I claim to be by no means an expert on Projectors (NOT even close)- I have only built from 'scratch' one single color open PJ -just to prove I could do it-

--- so I will be learning as we go thru the processes..

We will, however have lots of great help from others..

There are some basic steps that most should start with--
---most of these steps we already know but its still good to explain and put these into the correct order.


Your work area needs to be big enough to lay out the parts as you go.




Your DMM- PS- and tools need to be handy-

We shall start with a projector that has completely quit- or at least is not showing any laser(s) working.

If your projector has dip switches you must be sure these are not stopping your PJ from working so check these out thoroughly before removing any parts.

I would think making sure the power cord is working may be step one.


check the fuse--most are rigt below where you plug the power cord in - physically test it- it could be blown and not look blown.

Check every fan you can find to see if it is working-- HOWEVER some fans do not come 'on' until needed.

These are mostly the ones mounted directly at the rear or on top of the laser heads. If the head is actively cooled with a TEC the fan may never come on. Fans located at the rear or sides of your PJ's case SHOULD be running whenever the PJ is powered up.
Some parts in projectors need to be insulated from the baseplate or enclosure- These will have a white plastic insulator washers on the mounting screws , a flat thin piece of grey 'rubber' under the head or both.

IF you fail to do this any new parts you add may not work or may even fail.

Don't assume because it was fine at one time that the cord or fuses may NOT be the problem, in fact I check the basic things each at least twice.

Second might be the off/on switch and /or the key switch. An inexpensive DMM can be used for these tests.

If NOTHING happens next check and confirm that the fuse is still good-- you can use a battery and a flashlight light bulb to see if the fuse is good or , of course, you can check with a DMM to check as well.

So from there we follow the wiring to see how far power is going. --

I suggest that you take pics as you work so you can refer to them later in case you get confused . I have four different colors of Sharpies and carefully mark each place I am taking apart-- both the end of the wire and where it plugs in(the socket). If the wires are red and black =you can use those colors of markers to be sure you are doing things correctly.


While you may think the fix will happen quick it could take much longer and counting on your memory may be a mistake. I use a fine tip sharpie to make abbreaveations on the PCB-- like 'F' for the wire that goes to a fan. Your wires may be zip tie wrapped and this makes following them a tad harder. SO you may want to cut these carefully to make working with them more easy.

And later it would be a good idea to use new ties to nearten the wires back up when you are done. Personally I would not use glue on the plugs- when putting the parts back together. I use an exacto knive and a pair of hemos to remove the hot glue some PJs come with. none of the LKs have white hot glue..

Some parts -- for example a driver board for one of the lasers can be hooked up to the wires from the defective one and tested BEFORE you go ahead and remove the old driver. So I hook the wires up BEFORE removing any part- test it and if the problem is fixed THEN I swap out the two parts- I put a 'NG' on the bad one (No Good)--if you follow this you will never put the old part back in by accident.
-


If your projector is 'flat lining' either a horizontal or verticle line you prolly have a probelm with just one of your two galvo 'engines'- swap wires to confirm. Put them back in the original places after you quit.


If you are only getting a dot-- then neither glavo is working- to confirm remember to test in each way you can.

If one galvo is working you still may have or want to replace both-

The galvo makers match then when they are tuned and getting just one and having it wiork with the good one may be a harder way to go- especially with low cost galvos-- If you have the high price ones you may want to try just buying one.

Do not buy more glavos until you confirm that the scanner amps is working properly- these are quite often the problem and you do not need to buy an entire set if the problem is only the amp.

If your PJ has DMX and you can use that -it needs to be tested with DMX - try with the built-ins and the sound response- the mic may be bad so tap on the PJ to see if something happens-

If yours can be ran by PC then try that too. - with the PJ powered up check each connection and watch for any new change.

I use the eraser end of a pencil- and gently push each connection on all the PCBs and places w=here the wires connect. A flashlight helps to see better-

I keep a small magnet stuck to my screwdriver to 'grab' screws for me- then move them into a film can marked for later-- it too has a magnet inside..


don't be intimidfated by the insides of a PJ. Yes there are lots of things going on in there but with a little study and common sense most of the myseries will go away-

here is what the inside of George's LK PD2 looks like:

btw another test I do is the 'sniff test' some parts make a distinctive smell when they die- if you get a burnt electronics smell from the amp that can be very telling.

this odor fades in time so when a PJ fails its best to open it up and take a whiff.

Sorry for that unfocused last pic- it shows the place where the fuse is.. I use a small flat head screwdriver to gently pry it open.

So I have followed the incoming power thru the switches and see the ground attached to the base.
next pics show where the AC goes into the amp- and next is six places for plugs biut only 4 are used- beneath each reads 12vdv- so i will check both these next with DMM.

To make access easier I have partially detached the back plate without un plugging anything and have rolled it up onto the top of the case. If I dont get the right AC here the problem is with the key switch or the other switch (unlikely IMO)
If I dont get 12vdc from all three that I can easily access then i think the amp must be bad. To prove that I CAN take a working amp from another LK PD2 but of course would rather not have to do the swap. The two with the sky blue insulators are the (100 to 200 VAC"AC) in- the 12 vdc out are the small ones next to these two-

Power goes back out of the amp to do the 12vdc for all three lasers- and power to the galvo's driver PCB. --

more on tuesday--

good info... thanks for sharing this!

hey-- it is as much for me as anyone else- like building a hand held --its good y=to know how to fix one too. There is great satisfaction to both building a laser projector and being able to fix one. For me knowing what was what 'under the hood' was as scary as it was/is for anyone- If you understand a very simple one color DIY PJ then the other parts in a more complex PJ as less mysterious.

BRB with new info on the PJ we are working on..

hk

OK Hak now what are you up to

ha ha up to my bunghole in PJs in need of repair- but need to learn and i include stuff like this into my GBs-- made some progress today- the power supply amp inside is fried- 117vac going in just fine but tested two 12vdc outs next to the AXC in and no power from one less than a few vdc from the other- I am guessing this problem may be one of the more common actaul fails- good to see that the REKE was fixed in another thread by checking to see if all the wires are plugged in correctly. So I will bb asking Linna to express me a new PS for Georges's LK PD2- and hopefully thats a fix done-- the only other repair i have ever done was replacing a FS mirror in a DJs RGY stepper PJ- and it had a pound of dust inside it too.

Next another Lk PD2 with a low outputting green and it is NOT the green module (its was already replaced) so-- that leaves , I guess the show card--

time to call upon my A-Team one is here now Jeff has no fear- and he also owns a LK projector -- DZ will help us as well-- be sure to thank those that drop into this thread and share the knowledge --hak

ok. I've been wondering if my green seemed too dim. my "yellow" has been looking oranger, which I suppose a weak green could cause. I know the 638 and 532 in it are both supposed to be 100mW, yet when it projects a 3D red image, it seems brighter than a 3D green image, which should not be the case if both are truely 100mW subscribing

I'm a little afraid to tinker with the inside of the PD2, but we shall see.

baby steps

we can do this--
and wont be alone--

calling the calvary-- I have two LK PD2s here and wil do some pics tonite however its too easy to see the green is all but dead-- LOOKING--- but its a new module - both parts - I GAVE what we([me] Alex-Jeff and Dr Sam at SELEM) thought was the 'bad' one away for use in a LUMIA and the new owner tells me its working fine- its NOT the green module-- HOW do I verify this??-- must I swap parts with my known working model??

SOS

hak

hakzaw1 said:

its NOT the green module-- HOW do I verify this??-- must I swap parts with my known working model??

Click to expand...

Hi Hak,

I wouldn't pull parts from a working projector unless you can deal with possibly having 2 projectors with issues. I'm not familiar at all with the projectors you're talking about so I'm kinda taking a shot in the dark. Does each laser have it's own independant driver? Or is it a one circuit board for all? Certainly the first thing to check is the connection from the power supply to the driver itself and verify you have proper voltage at the driver, not just out of the power supply. I would be sure to check this voltage when you have a full +5V modulation signal to the driver. Are you running this projector with an external DAC?

Did you guys give the greens some time to warm up? Some times if it's cold out they'll have diminished output. They may also get too warm. I found on a TEC-stabilized green I had that it took about 10 minutes to stabilized; however, that was for a 500mW. With these fan-based greens.

One thing I like from the pictures I see above (I don't own an LD2), is that the manufacturer didn't feel the need to pot their circuits the way many manufacturers do. It shows that they're not too concerned about people ripping off their circuits, and that you can do debugging yourself.

DZ you know me TOO well and I agree- will HAVE to pull the bad one so no harm doing that--

I will run these again for more pics and use FB3-
will try with both alone - daisey chained together and the other way around-


@BB yes I have ran that PJ several times for more than an hour next to one working perfect- it looks lkie 2 maybe 3 mW- the one in this PJ is new- it repalced the first one that I was mistakenly thought it was bad- The guy who has the first 'bad one' sez it work right for him.
so when the green module is ruled out what gets checked next?? This is a TTL 7 color-

Combined before losses ~.5W--

brb w/ a pic


THANKS for chiming in my friends!!!










pics side by side

want more??

Bionic-Badger said:

Did you guys give the greens some time to warm up? Some times if it's cold out they'll have diminished output. They may also get too warm. I found on a TEC-stabilized green I had that it took about 10 minutes to stabilized; however, that was for a 500mW. With these fan-based greens.

One thing I like from the pictures I see above (I don't own an LD2), is that the manufacturer didn't feel the need to pot their circuits the way many manufacturers do. It shows that they're not too concerned about people ripping off their circuits, and that you can do debugging yourself.

Click to expand...

_LK wil customize any PJ so its also in their own interest to keep the white glue gun at home.
They also will work to fix remotely-

I just sent Linna the link so we may see some response soon..

>$80 to express ship -- no win- she sends the part and helps repair- win win

Try powering the green from one with the PSU/card from the other. It should be just like jumpering it over.

hmm dont follow-
you mean daisy chain DMX- i dont have DMX box yet
I CAN run both from Beyond- they have both ilda in and thru-
& I can swap them around-- but I expect nothing to see different-
The green looks weak no mater what-- when new it was fine AFAIK- 9 it was sold to another GBer) at some point in time james said the green looked weak- and it was- - we got a replacement module(in 72 hrs!) (head and driver) -swapped and no better

I can wrap my head around a weak analog laser- its maybe not at full power-- BUT TTL is all on or all off right? I can pull it and swap with mine but really dont expect a solution that easy-- btw i gave the old green away to a friend who sez its working as it should-- so-- as i am about to request parts from Linna/china I kinda need to know-- what else do we need. guess i should not worry about the cost of shipping on Linna- but do feel bad as i know she does a proper round of testing just prior to boxing--I could not get Lasersman/Yourlaser/dinodirect/laserpointerworld[they are all the same place] to even plug mine in. and I had two orders of twp PCs paid for--


The factory seals from REKE were intact- and more than 70-% arrived needing some work -- turned out... all they were worth , at best , was the $209 we paid for them



OKAY BB I just read that again- try swapping the show cards in place- thats possible i will try -- since i will have georges opened up to remove the amp I can learn more about swapping-

good idea
will try back later

What I mean is that when troubleshooting, you want to isolate the problem by using known-good (reference) parts to determine exactly what the bad part is. In this case, you have the unique advantage of having a known-good projector to help test the bad projector.

This is your problem setup:



But where is the real problem? The laser? The PSU? The controller card? You need to isolate the source of the problem.

First see if the replacement laser you receive is actually good. Maybe it isn't. A good way to test this is to run it using the reference projector's power supply and control:



If your laser is still misbehaving like before, the laser is probably at fault. If it's not, try something else, such as testing the laser's power supply. You can do this the other way around too, by testing the known-good laser with the bad PSU:



In this case, if the good laser works just fine, the PSU/control is probably good and the laser is not. If the good laser is underpowered, the PSU/control is probably to blame. There's always a risk that the bad PSU may damage the good laser though (or the other way around), but it's probably going to be fine.

But is the problem the control or the PSU? Let's test the PSU first:



Now you're controlling the modulation of the laser with the known-good projector, and powering it with the bad projector's PSU. Remember to share ground references. Is the laser under-powered? If so, the PSU on the bad projector might be to blame.

Conversely, you can use the good PSU's power and use the control of the bad projector to again see if the PSU is at fault or not:



Basically just follow through with this kind of process to isolate the points of failure. It's a lot easier for you to do since you have a working projector. Other people may have to do the troubleshooting by measuring values or providing alternative power sources, etc.