Somethings moving

[Insanity]

So I'm at my wits end with this one. I have run out of ideas as to what is going on...

9 times out of 10 when I switch on this projector, on the horizontal lines, I have a green line sitting on top of a magenta line. As the image is going through a scanner pair, this shows that something is moving laterally and that something would appear to be the green laser. Now, here's the thing; the other two projectors are built exactly the same and nothing is moving.

As a test, I fired the green over 15mtrs and made a box of masking tape around the spot, where the edges of the box just touched the spot. After an hour, the spot was still bang in the middle of the taped box, so I'm sure there is not a problem with optics moving inside the green module. I then fired all 3 modules at the same point, after 30 minutes they were still aligned perfectly. I can't show you the spot, as things went a bit wrong but this picture does illustrate the damage lasers can do.



The laser has two shims like the one in the picture underneath it to bring it up to the correct height, everything is coated in thermal paste, so laser to shim, shim to shim and shim to base. The base is 10mm thick and has a 40m thick heatsink underneath, again with thermal paste, the heatsink has 4 C@sio fans blowing over it, so I am pretty sure its not heat problems.



The laser is bolted down with 4 M3 screws and I have used washers increasing in size to cover as much surface area as possible. These were done up with tee handled allen keys to get the best possible purchase, so they are tight.



So, I have given you as much detail as I can, and tried to cover all bases in mounting the laser...

Here's the thing, despite everything I have done, I can twist the laser very easily with my hand. I can't see anything move physically, but them I'm sure the movement is tiny. But on the output image, this is very apparent.

Here is a crappy video to try and show what I mean:



If anyone has any ideas, I would be eternally grateful

Cheers
Mark

[badger1666]

hi mark
look like the 4 little bolts on the underside of the laser, that sandwich the base/tecs to the laser need a tweek up
they are proberly just not tight enough and allowing the base or laser to slide on the tecs
thats all i can i think of

[White-Light]

Marc are the bolts through the laser very tight into the holes on the the laser module in a lateral sense or are there slight gaps (could be less than a single mm)?

I'm going to take a punt here looking at the shims and say that maybe the holes in the base of the laser or shims are very slightly larger on that one laser meaning the laser can move very slightly side to side under twisting whereas maybe the bolts are touching at the side on the others - even if not touching both sides of the bolt holes, the bolts on the others could potentially brace it by touching opposite sides whereas maybe the bolts aren't quite meeting the sides on this one.

[danielbriggs]

Mark,
What I think Alan's trying to say is, that you have a screw loose.

[steve-o]

^lol
There appear to be wires sandwiched inbetween the laser head and the mounting base ?? Or am I seeing this wrong ..

[Steve Milani]

Hi Mark

I am not so expert.... so...I try to guess what the issue could be , thinking by...exclusion of cases.

1) after 15 minutes on work (this means warmup time completed more than needed) the spot stay always in the same place. Apparently, there are not any issue of thermal dilatation of metal components (optic mountings) inside the module.
2) if you try to force the module to change its position on the main baseboard, something happens ( the spot return to be in the right position or it change anyway his position). All this happens without you have the real sensation you moved physically the module.... but ... it does happen!
3) All bolts are well locked. The module is 100% locked and well on level surface of the baseplate.


I thought about this answers:

1)Inside the module there is some very little bolt, used to lock optic mountings, that isn't locked well. I say better: these bolts are next to be "microscopic"... Maybe some of them SEEMS to be ok... It seem to be locked.... instead its thread could be damaged.... Maybe the metallic mounting which has this issue, has such dimensions as to go in contact with the external closure of the module (the "cover" of module). This could be the reason because, when you try to move the module, this little force applied on the cover can induce a very very little movement of the mounting which brings optic.

2)Because some bolt inside module could be not ok, vibration of the case fans can induce movement of some optic mountings. This is a very difficult situation to be.... but it could be! Micro-vibration are very hard to discover and very dangerous also. I well know them... (36 years into Navy - Engineer)

3) Some "cold solder" of wires inside module body. Touching and forcing to move the module you move the cold solder point, changing a litte the values of impedence, ohm, volt and ampere, microFaraday... etc. etc. into driver card.

4 and last) Even if I'm sure you already done.... Please check the ground connection and all power wires/connections of module.

I don't believe in "Gremlins"... So... your last resource is a PM to *Stanwax* or "Bridge*

I wish you can fix issue soon.

Greetings!

[Steve Milani]

^lol
There appear to be wires sandwiched inbetween the laser head and the mounting base ?? Or am I seeing this wrong ..

Holy crap!
It could be real! You hawk's eye mate!

[White-Light]

Mark,
What I think ... you have a screw loose.

Not loose just that there can be lateral play even with screws tight sometimes where the screw threads don't butt up fully to the sides of the holes when you're trying to bolt items consisting of several layers of items together as there's more of a tendency for them to glide on each other.

- - - Updated - - -

Holy crap!
It could be real! You hawk's eye mate!

What he said in 15 characters.

[andy_con]

oh alan...

I love how someone whos never built a projector before is offering building advice!

don't you need a 3.2mm clearance hole for a 3mm bolt? aren't thought holes suppose to be wide enough for a screw to pass through not to touch?

you learn something new every day

[White-Light]

I've built plenty of other things to know this can be a problem where you are bolting multiple items together. Single item no issue you can have wide holes and screw down tightly, the item is unlikely to shift. Multiple layers and you're much more prone to sideways slippage.

Anyway, looks like the wire may have been the cause.

...and btw the names not Alan.