FB3 hookup - help!!!

[Stuka]

OKAY, I decided to use the "stock" FB3 connection to my scanners (ScanPro 30's), with no intermediate circuitry to complicate things.

Ignoring the interlocks and laser modulation inputs for the moment, the FB3 gives me the following connections across the ILDA connector:

X signal
X ground
Y signal
Y ground
Intensity signal
Intensity ground

My scanner amps have the following connections per amp:
(with power supply connected as indicated):

Signal in (-)
Signal in (+)
Signal ground
Scanner feedback
-24V
Gnd
Gnd
+24V


SO -
Can anyone who has hooked up the FB3, using similar connections, give a little tutoring on the proper connections to make here? I'm using the Pangolin LiveQUICK application with for my initial testing, with Buffo's recommended test frames from his scanner tuning tutorial. My initial displays have been nothing but an unrecognizable "glob", with VERY noisy scanners!!

Any assistance (before I blow something up!!!) would be appreciated - I don't even want to attempt tuning until I'm sure everything is hooked up correctly!!

Thanks in advance!!

Randy

[tocket]

Just connect X signal from the FB3 to signal in (+), X ground to signal in (-) and also you can connect ground on the FB3 to signal ground on the galvo drivers.

Intensity is for laser modulation and is nothing you need to worry about. Just use the regular channels.

The glob sounds worrying, how did you hook them up to get that?

[Pangolin]

Hi guys,

Stuka, are you geographically close to anyone else on PL, so that they can give you some help hooking this up? It is pretty easy, but somewhat difficult to communicate about it over a text-based forum.

But I do want to correct one thing, and it is something that is really subtle and easy to overlook. You should NOT!!! connect the "ground" of the DB25 ILDA signal to the "ground" of scanner amps!! In fact, you should not connect anything at all to the "ground" of a scanner amp (except for the "common" wire of the power supply).

Each scanner amp has a "ground". If you tie a signal wire (such as the so-called ground of the DB25 -- pin 25) to these grounds and also connect the power supply common to these grounds, then the scanner amps will actually have two separate ground paths, thus you have a "ground loop", but I really hate to use that phrase because it is way over-used. This will give you distorted graphics. The distortion can be subtle, but it is there.

The pictures that I take when I do a mod of the DT-40 (fully documented in another post) are not only with the mod, but also with the X- going into the X- of the amp, X+ going into the X+ of the amp, and NOTHING connected to the "ground" of the amp (except power supply common).

Then, after all of this, what you do is tie pin 25 on the DB25 to the POWER SUPPLY ground pin itself.

What you are trying to accomplish here is what's known as a "single point grounding scheme", otherwise known as a "star grounding scheme". I will let you guys look this up on Google or Wikipedia for more information...

Anyway, what you want is for all "ground" wires to meet at one, single place, and that place should be the power supply. Doing anything else will give you sub-optimal images.

Now, with this having been said, I bet a few of the professionals on this forum will re-wire their projector and get better performance. Stated another way -- I will be willing to bet that a good majority of "professionals" -- even those making laser projectors, do not know this...

Best regards,

William Benner

[Stuka]

Bill -

Your grounding recommendations make sense.
What is your recommendation for the (-) amp signal inputs, when using a single-ended board such as the FB3?

[Stuka]

OKAY - here are my initial results:



This is the square wave pattern recommended in Buffo's tuning tutorial!!
Using LiveQUICK, single laser, geometric correction set to 50% (I'm assuming that's the way you adjust scan angle?). Projector approximately 3 feet from wall/screen; image approximately 12" x 12"

FB3 connected to ScanPRO amps as follows:
X signal to X amp signal in (+)
X ground to X amp signal in (-)
Y signal to Y amp signal in (+)
Y ground to Y amp signal in (-)
BOTH scanner grounds & DB25 pin 25 connected to amp power supply common.

Any suggestions

PS -

The scanners are buzzing like a portable electric engraver while making this image!!

[tocket]

But I do want to correct one thing, and it is something that is really subtle and easy to overlook. You should NOT!!! connect the "ground" of the DB25 ILDA signal to the "ground" of scanner amps!! In fact, you should not connect anything at all to the "ground" of a scanner amp (except for the "common" wire of the power supply).

Thanks Bill. I've always wondered what the point of connecting the "signal ground" pin on the galvo amps was. I couldn't see any reason to do it, but it was one of those "everyone else is doing it, so it must be correct" things. Now begs the question, why do the amps have a "signal ground" in the first place?

Surely it's not intended for single-ended signals as that would leave X/Y- floating and that certainly doesn't seem like a good idea.

A question about the FB3 though; what is pin 25 (of the female DB25) connected to? Looking at the pin assignment in the manual one might think it's not connected to anything.

[Stuka]

Here are a couple more photos, same conditions as previous image with one change - the DB25 ground is now disconnected from power supply common:



And in this one, the laser output is turned off in LiveQUICK:



And yes - the scanners still buzz while generating any image...

[jmilan]

someone has the link to this post...?

Thanks, JM

Hi guys,

The pictures that I take when I do a mod of the DT-40 (fully documented in another post) are not only with the mod, but also with the X- going into

William Benner

[buffo]

Randy;

I can't see your pictures (blocked here at work), but it sounds like you've got a serious problem.

First, double-check that X signal on the FB3 is connected to X + on the scanner amp, and that X gnd on the FB3 is conencted to X - on the scanner amp, just as Bill posted above. (Obviously, the same thing goes for the Y axis)

Now turn your scan size down to around 15% and see what the image looks like. If it's still messed up, then there is another problem.

Adam

[Stuka]

Yep, something definitely "ain't right" with the setup!!
I'll double-check all the connections when I get back this evening from playing Army.

Is it safe to assume that when working properly, the scanners should generally be operating with little or no noise?

Randy;

I can't see your pictures (blocked here at work), but it sounds like you've got a serious problem.

First, double-check that X signal on the FB3 is connected to X + on the scanner amp, and that X gnd on the FB3 is conencted to X - on the scanner amp, just as Bill posted above. (Obviously, the same thing goes for the Y axis)

Now turn your scan size down to around 15% and see what the image looks like. If it's still messed up, then there is another problem.

Adam