Modulation issues with RGB Analog projector

[catalanjo]

Hi ...I think the first easy thing you need to do is to post WHERE in New Zealand you are based ...this might encourage members who are close to get involved.

I think the green cutting out instead of reducing may well indicate that the module is a DPSS module not a pure diode.
This means you are modulating the pump diode which has a minimum threshold to lase and is very tricky to get right without an add on colour correction card.

The red not responding to modulation reduction might possibly indicate that it is being horribly over driven (often done in China to achieve a better white balance).

What kecked meant, was to first confirm that it is the projector that is at fault by interrupting the signals BEFORE they get there by breaking out the ILDA cable.
Link for nonsolderers. "http://www.ebay.co.uk/itm/381443658572?var=650595074641"
Product title " D-SUB DB25 Male / Female 25Pin Plug Breakout Board 2 Row Terminals Connectors"
With a male and female version you can swap signals around using just a screwdriver (be careful) and unplug both ends of cable before trying to re-wire. You can find ILDA cable pinouts in internet with no problem, or just ask here.

This would at least confirm that the problem is not at the control end.

If you can't manage this, and you can't solder, ... then you will have to get help on this ...so post your location (fill in your profile) it does not have to be very exact, and maybe contact any member who is in NZ via PM ...I think this is your really only hope.

Hope this helps a bit

Cheers

[ReaperZ]

Hi ...I think the first easy thing you need to do is to post WHERE you are based ...this might encourage members who are close geographically to get involved.

I think the green cutting out instead of reducing may well indicate that the module is a DPSS module not a pure diode.
This means you are modulating the pump diode which has a minimum threshold to lase and is very tricky to get right without an add on colour correction card.

The red not responding to modulation reduction might indicate that it is being horribly overdriven (often done in China to achieve a better white balance).

What kecked meant, was to interrupt the signals BEFORE they get to the projector by breaking out the ILDA cable.
Link for nonsolderers. "http://www.ebay.co.uk/itm/381443658572?var=650595074641"
Product title " D-SUB DB25 Male / Female 25Pin Plug Breakout Board 2 Row Terminals Connectors"
With a male and female version you can swap signals around using just a screwdriver (be careful) and unplug both ends of cable before trying to re-wire. You can find ILDA cable pinouts in internet with no problem, or just ask here.

If you can't manage this, and you can't solder, ... then you will have to get help on this ...so post your location (fill in your profile) it does not have to be exact ...I think this is your really only hope.

Hope this helps a bit

Cheers

This helps a LOT !

The green is definitely DPSS as its 532nm .. solution, buy a 520nm full diode to replace? I'm happy to do this ! any reccomendations of where I can buy a decent 520nm module from? I believe I need 20-25% more 520 vs 532.. as my system is 200mW 532 I'd need to source a nice 300mW (or more if theres a benefit) 520nm.

The red being horribly overdriven, bloody china

I will purchase the ILDA breakout and study the pinout for it .. but part of me wants to just buy a replacement green (520nm) and replacement red (638nm) and put them in and see what happens.. worst case scenario I will know I have decent quality driven modules

By the way my location is New Zealand, so unlikely to find help here I will update my profile!

[catalanjo]

Hi, yes sorry, I noticed that from your first post and edited my comments accordingly.

Red being over driven is just a possible theory not definitely the case (China has advantage of being cheap!).

Before going overboard and changing modules (green is NOT cheap) it would be wise to check that source of problem is not control end first.

I think you are also a bit mixed up about which card is which in the projector, as kecked points out what you consider to be the red and blue drivers are in fact the scan amps (unless the pics are mislabeled).
This you can verify since they should connect direct to the scanners and are much larger than any driver board.

My memory is like a sieve these days but I am pretty sure there is someone in NZ who is a member here. When I remember I will post here.

Cheers

PS. Post more detailed pics so as to identify the driver boards for red and blue !

[ReaperZ]

I'll recheck my pictures and boards tonight and take more photos .. unfortunately its all packed in quite tight making pictures not the easiest. the boards in picture 2 and picture 3 are exactly the same size, however ill retrace the wiring to make sure

I've emailed a local electronics retailer to see if they sell the breakout board for 25pin

Thank you!

[catalanjo]

@ " I've emailed a local electronics retailer to see if they sell the breakout board for 25pin" = not a hope, use the link I posted !

Problem with green diodes (a part from price) is that between 150mw and 700mw there is a big empty space !
You could however use 2 x NDG4216 knife edged or with PBS cube or for similar money go to a 9mm NUGM01T 1W 520nm (both available from DTR in USA) but the beam will be fat on the latter, so you would need correction cyl lenses from dave in OZ (lasershowparts.com) who has most everything you might need, ..... both members here on PL.

Pretty difficult recommending a course of action with so little info available and even more so if you have no electronics skills/equipment.

= search KIWI = Kiwi language skills = Started by daction, 06-22-2015 06:49
daction ...... Senior Member Join Date Nov 2009 Location Whanganui New Zealand
According to him "The english never claimed the wanganui river." ..... so he probably knows quite a bit about green modules.

Don't know him personally but U could try a PM. and see if he can help you out.

Cheers

[dkumpula]

I just read this thread from the start folks and I think its possible that we haven't fully identified the problem and jumped directly to solutions. Because we love to fix things! Perhaps it would be helpful to describe what *should* be happening and then move onto the symptoms and finally describe the range of possible root-causes and associated solutions? Please forgive me as I will restate some of what's been said already as well as for stating what most regulars in this forum already know.

What Should Happen:

So let's assume you had an analog projector that was built with top quality parts and carefully set up for an end user. With bias properly set and in the case of the green, TEC that was set carefully, you should be able to ramp up each color from 0-100% and see a generally linear increase in apparent brightness. Ideally, red, green and blue should all come on as you ramp up at the same time (preferably close to zero). The green, being a 532nm module will start by jellybeaning (producing a dim dashed or dotted output), but that's the just the nature of DPSS units. The 532nm will also likely have plateaus or even slight decreases in output as you ramp up the modulation signal, but again, that's just typical of DPSS. The output of the other two, being direct diode units, should ramp up fairly linearly all the way to 100% modulation signal.

What Is Happening (Symptoms)

We have (or we believe) pictures of the same frame displayed in red, blue and green with BAM set approximately to decrease output to 30% at roughly the lower half of the image. Red shows no apparent change and appears to be fully on for the entire image. Green shuts off fully in the BAM region. Blue dims significantly in the BAM region.

Potential Causes

Blue: This one is the easiest as it looks roughly like we'd expect. Output is dropped significantly in the BAM region. So the blue module is analog and is decreasing output when set to 30% to a visible level clearly between fully off and fully on. This doesn't say that blue will start up cleanly at a very low modulation level (1-5%) or ramp up fairly linearly until topping out at 100% modulation, but at least its something.

Green: Being fully off at 30% output could be several things. Despite what the manufacturer said about the replacement driver, it may have be another TTL module. It could also be a driver that can do both TTL and analog, but is currently set to TTL. If the driver is indeed analog, it also may be a temperature problem where the TEC wasn't set at a level where the green would lase at 30%. (Likely set to be too cool). Setting a 532nm module for generally linear ramping of its output and stable output at any set level is not trivial and takes some experience, time and finesse to get right. If this is the case, simply swapping out the module without proper instruction was probably poor advice by the manufacturer. To help narrow down the analog vs TTL driver issue, I'd test your laser at a wider range of output levels. Does it come on at approximately 40-50% fully with nothing below that point and no increase in brightness between the on point and 100% modulation signal? If so, its TTL or set to TTL. Otherwise it just needs some TLC to get bias and the TEC temperature set to the right levels.

Red: This one is the most challenging in my opinion. It could be a TTL module that is kicking to 100% a bit early for a TTL module. (Most cheap Chinese TTL drivers flip from off to on at about 2.1 to 2.4 volts in my experience.) It could be what I believe Kecked and/or Cat were saying - the red output is hitting 100% way too early. This could be caused by modulation being 'artificially' ramped up too far by power problems in the projector, problems with the driver, or something artificially increasing the gain like the DZ Colour Modulation Boards that Stanwax sells. (I'm sure you don't have one of those in your projector, though ) Again, I'd try outputing the image at several output levels and see if you can find a range where you receive analog output. You can also measure the modulation signal into the red module when it isn't displaying anything and when it comes fully on. It should be 0V when you aren't projecting anything and fully on should be around 4.8V with a generally linear ramp in between fully off and fully on.

I've left out tons of things that could affect output to a lesser degree, but they aren't likely root-causes and this post is already too long. (Apologies to all.)

One last thing - the software. I don't use Quickshow, so I don't know, but many software packages have the ability to tweak the output levels for red, green and blue individually. This allows you to make sure they all come on at the same point and ramp up fairly evenly. This is really handy for artificially correcting less-than-ideal builds.

<Edit> Oh, and does Quickshow have a setting to force TTL behavior by color? If so, this may be set incorrectly for red and green. </Edit>

I'm sure I'm missing something in my analysis/comments above, so please point them out.

Cheers!

-David

[catalanjo]

Excelent post David.
@ "<Edit> Oh, and does Quickshow have a setting to force TTL behavior by color? If so, this may be set incorrectly for red and green. </Edit>"
As far as I know, in QS you choose TTL or analogue for the whole projector not for each colour separately! However it does allow you to raise and lower each colour separately for any given frame which should expose any cutoff point.

@ "I've left out tons of things that could affect output to a lesser degree,"
Without writing an entire book and with the very sparse info available up to now, this is kind of inevitable.

@ "this post is already too long." ... I disagree here, ..... any shorter and it wouldn't have covered the topic properly !

My primary aim was to get ReaperZ started in the right direction so as to learn a bit more and be able to follow kecked's initial advice, so as to isolate and pinpoint the problem. Secondly to try and generate some extra interest in the thread, as it seems to have been largly ignored by experienced members who might be able to help. (Seems secondary aim got a bit of a result).

I agree entirely with your analysis of the situation, many thanks for chipping in.

Cheers

[dkumpula]

Thanks for the kind words, Cat!

I failed to mention that I agree with Kecked and your assessments on what to do to actually address the problem. Sadly, fixing problematic cheap Chinese components is beyond the capabilities/tools at the average new-laserist's disposal, so looking for local assistance is probably advisable. Like many of us, I learned the pains of 'buying cheap' the hard way, but thanks to the folks in this forum, I learned enough to start bailing myself out and eventually building better projectors from scratch. Knowledge not shared is knowledge lost, and all!

Oh, and thanks to both of you for calling attention to the thread. Sometimes things get buried suddenly on PL if the activity levels spike. This time though, I wonder if it was all the SELEM activity that had half of the active PL folks distracted. I think I'm still recovering from that myself!

Cheers and thanks again,

-David

[ReaperZ]

Hi David,

Thanks for your well detailed post, its very appreciated!!

catalanjo is correct, QS sets modulation in the following ways : TTL, Analog with linear response, Analog with log response rather than per color. I'm using Analog with linear response.

What I will do this weekend is test modulation further with each of the colors via two ways
- adjust BAM from 0% - 100% in 10% increments, and observe each colors behaviour, displaying the same frame in R, G, B
- figure out how to manually adjust color levels of a frame inside QS, as another alternative on seeing the cutoff points of the laser modules.

Regarding checking voltages, where would I place the multimeter to observe this? I might just poke around and see what I can find, but dismantling it to see where wires go can be tricky given how tightly built it is, it may just take some patience from my end with labelling where everything goes and slowly dismantling.

Once again I appreciate all of the help provided here, and love having the opportunity to learn, if not break something

[dkumpula]

Sure thing, ReaperZ! Your acceptance of the risk to fix something is a healthy attitude, albeit a slippery slope to laser-inflicted-poverty that many of us here share.

Regarding using a multimeter to test your modulation voltages, did your projector come with a feature such as DMX control/auto-mode/music mode? If so you'll have a board in the projector that the ILDA input/output connectors connect to. That board probably has a sticker on it that says PT-iTrust, but might not. In either case, that board will have output on it that should be labeled red, green and blue. Each of these pairs will then travel to the driver for each of your three lasers. You can disconnect those pairs and test the voltage across each pair of lines. It will vary between 0 and 5V DC. If you don't have such a board (or even if you do) you can measure the appropriate pins from your ILDA connnector. Just refer to this diagram to figure out which pins are R+/R-, G+/G-, B+/B- and test the voltage across them.

Best of luck and let us know what you find.

-David