Galvanometer amp ID... no trim pot labels

[robotarmy]

Hey guys, I mentioned this in another thread about an argon laser i'm playing with but i figured i should stick it in the right forum.

Anyone know what this is?

I'm trying to figure out what the pots are on this amp so I can tune it. It was connected to a Chameleon PM21 controller and drives a pair of G120D scanners. I've got a connector pinout, but nothing else. It's got a centre tapped 20 VAC transformer to go with it, so the smoothing and regulating is onboard (bipolar supply for opamps, 7815, 7915 and 7805 regs onboard) There's some 5-pin to220 packages at the bottom, audio amplifiers maybe? Motor drivers? They have the part numbers scratched off.

Scanners


Amp


Blurry controller

[p1t8ull]

As you may already know that's an early Chameleon Tech dual channel driver you have there. You have gain, servo gain, velocity, twist and offset for each channel. Anticlock was always down/reduce on the prod amps so if this one is the same and you can display some kind of pattern now, you should be able to work out the pots with careful gentle tweaking and seeing what changes, otherwise George McDuff may be able to help ya

[mixedgas]

As you may already know that's an early Chameleon Tech dual channel driver you have there. You have gain, servo gain, velocity, twist and offset for each channel. Anticlock was always down/reduce on the prod amps so if this one is the same and you can display some kind of pattern now, you should be able to work out the pots with careful gentle tweaking and seeing what changes, otherwise George McDuff may be able to help ya

Odds are they are tuned well enough right now, it is very advisable when working with analog tuned show gear to let things be.

Do you have a oscilloscope?

Steve

[robotarmy]

Odds are they are tuned well enough right now, it is very advisable when working with analog tuned show gear to let things be.

Do you have a oscilloscope?

Steve

Yeah, good call man, but when i plugged the PM21 in there to test them out they oscillated something fierce. I think position detection is working because the out of range shutdown fired a few times. I've gotta get a proper working DAC to test them out properly. I'd love to get my hands on a working PM21 for a few days, just to figure out the signals and see if the amp is working, if not i'll probably just abandon the G120's and get a matched scanner/amp set, or try and build my own digital amp

[mixedgas]

Also, my bet is that is close to a Laser media LM22SDA or a factory G12o simple amp with a newer output stage, re engineered as a double... translation, I bet I have a schematic that is close enough for you to figure out whats what.

Steve

[robotarmy]

Also, my bet is that is close to a Laser media LM22SDA or a factory G12o simple amp with a newer output stage, re engineered as a double... translation, I bet I have a schematic that is close enough for you to figure out whats what.

Steve

Awesome! The man with the plan... what, do you have the universe's biggest filing cabinet labeled "Schematics"? Kick ass

ps.. x and y could totally have been swapped.... are different galvos really THAT different? The mirrors are the same sizes...

[300EVIL]

Awesome! The man with the plan... what, do you have the universe's biggest filing cabinet labeled "Schematics"?.

Yes he does, the rest is in his brain. Gotta find the download button...

[mixedgas]

Awesome! The man with the plan... what, do you have the universe's biggest filing cabinet labeled "Schematics"? Kick ass
end quote

If you have a problem with that, I can always burn the wall of 3 ring binders......

ps.. x and y could totally have been swapped.... are different galvos really THAT different? The mirrors are the same sizes...

end quote:


If you have a problem with that, I can always burn the wall of 3 ring binders......
GSI 1xx or 3xx can be, most more modern stuff, no.

Start HERE: http://www.skywise711.com/lasers/scanner/scanner.html
And HERE:http://www.camtech.com/archive/12pcx_CX660.pdf

If that doesn't work, I have one more back home.

Thanks to Skywise for hosting the PDF.


Steve

[Yag]

I get mad oscillations from my PM controller (PM20 I think) if it's left turned off for long periods and the memory battery goes flat. I can clear this with the reset code.

The scanners/amps may well be OK.

[robotarmy]

I get mad oscillations from my PM controller (PM20 I think) if it's left turned off for long periods and the memory battery goes flat. I can clear this with the reset code.

The scanners/amps may well be OK.

HOLY CRAP it worked!!

Sweet, i don't think the amp is tuned properly as it still hits the position limiting etc, but i'll have to trace that out sometime. The controller is putting out a fine signal now Thanks for your help yag!

[robotarmy]

end quote:


If you have a problem with that, I can always burn the wall of 3 ring binders......
GSI 1xx or 3xx can be, most more modern stuff, no.

Start HERE: http://www.skywise711.com/lasers/scanner/scanner.html
And HERE:http://www.camtech.com/archive/12pcx_CX660.pdf

If that doesn't work, I have one more back home.

Thanks to Skywise for hosting the PDF.


Steve

I got a set of schematics and a silkscreen that was missing from this board. If you want a copy for your archives let me know

The 4 pots are labelled Gain, Offset, Position and Velocity... that seems to correspond well with the tuning instructions in the first link up there. I'll give it a shot tomorrow and see how it goes! Thanks for the info man!

(the 5th pot is labelled twist, which apparently can be enabled by a jumper... not sure what that's about)

[mixedgas]

yeah. we'll put in the archives
Steve

[Carl B]

Hi Robotarmy

I had one of these ChamTech driver boards quite a few years ago to drive some GS 325's, not realy any good for laser shows, and when I first got mine the little white relays would trip when I powered up.

If I've got this right this is how you stop the tripping.

1. Disconnect the PM21 from the input. Connect Galvo's.
2. You should see two jumpers shorted. When you power up the driver, do eather of the LED's in the corner below the trim pots light up Green or Red. These are bicolour LED's. If not then remove the two jumpers and look for LED's liting. I can't remember if you have the jumpers shorted or not for the next stage.
3. If eather of the LED's are lit then this means that the Offset trim pot is to far from center. What you need to do is turn the Offset pots until the LED gose out. Go to far and the LED will change Colour. Your aiming to have the LED's between the two lit states. If the trim pots click when you turn it then you are at one end and need to turn the other way.

Hopefully this should at least get you scanning some images. I'm not sure on how to fine tune the driver for better quality images.

Edit. On closer inspection of the photo of the Driver the jumpers just above the galvo sockets I have noted that they are not shorted so I think you have to short them out to set the Offset as above. When you have finished setting the Offset's you need to reopen the jumpers.

Carl

[robotarmy]

Hi Robotarmy

I had one of these ChamTech driver boards quite a few years ago to drive some GS 325's, not realy any good for laser shows, and when I first got mine the little white relays would trip when I powered up.

If I've got this right this is how you stop the tripping.

1. Disconnect the PM21 from the input. Connect Galvo's.
2. You should see two jumpers shorted. When you power up the driver, do eather of the LED's in the corner below the trim pots light up Green or Red. These are bicolour LED's. If not then remove the two jumpers and look for LED's liting. I can't remember if you have the jumpers shorted or not for the next stage.
3. If eather of the LED's are lit then this means that the Offset trim pot is to far from center. What you need to do is turn the Offset pots until the LED gose out. Go to far and the LED will change Colour. Your aiming to have the LED's between the two lit states. If the trim pots click when you turn it then you are at one end and need to turn the other way.

Hopefully this should at least get you scanning some images. I'm not sure on how to fine tune the driver for better quality images.

Edit. On closer inspection of the photo of the Driver the jumpers just above the galvo sockets I have noted that they are not shorted so I think you have to short them out to set the Offset as above. When you have finished setting the Offset's you need to reopen the jumpers.

Carl

Hey carl Thanks for the tips, but i think my offset is set right. I can display simple patterns but the test pattern comes out like a drunken teenager tried to draw it while suspended upside down from a really high cliff...

Maybe i should get some blanking sorted out and work on it some more then.

Does anyone have the laser media test pattern in ILDA format? I'd like to run some test patterns that don't require blanking.

[robotarmy]

... that seems to correspond well with the tuning instructions in the first link up there. I'll give it a shot tomorrow and see how it goes! Thanks for the info man!

(the 5th pot is labelled twist, which apparently can be enabled by a jumper... not sure what that's about)

Hey guys, i've got the test patterns i need and a tutorial on scanner tuning (i think written by buffo) that's a little easier to follow than the older ones that came with the G120's factory amps.

I'm wondering how my trimpots correspond to the labels in that tutorial, it's very well written and uses the test pattern i have, but the amp being tuned there has different names for the parameters, namely servo gain, HF and LF damping.

According to the guy from chameleon who made the amp i have:

V is velocity gain
P is positional gain
O is offset
G is input gain.

Do i need to use a different procedure? Does LF damping = positional gain maybe? HF = velocity gain? Someone mentioned the amp I have might implement PID control, so is the "positional gain" more properly the proportional gain? What about velocity gain? Servo gain = input gain? Maybe?

[gashead]

end quote:

Start HERE: http://www.skywise711.com/lasers/scanner/scanner.html

Steve

As it happens I've had one of these hanging around for years, and due to the credit crunch (My wife) I've decided to get it going again.

Anyone happen to know which pins are what on the input connector for the LM22SDA ? (P3)

The manual tells me everything else I need to know except which pin is which for P3.

I did have it working last night, after replacing the caps on the X side (which where burnt to a crisp from the previous owner) but I too, let the magic smoke out and am going to replace another two caps tonight..

Saying that, I do suspect perhaps the driver may have a fault (hence burning caps) was also running it with no input connected, which reminds me of the day I went to pick up this wonderful relic I bought on ebay, the chap was demoing it for me, and messing with the input (loose connection) and the thing popped it's caps tops and started flaming..

Was kinda funny.. he didn't have the guts to sell it to me at that point so just handed it over..

Cheers,

N.

[gashead]

Saying that, I do suspect perhaps the driver may have a fault (hence burning caps) was also running it with no input connected, which reminds me of the day I went to pick up this wonderful relic I bought on ebay, the chap was demoing it for me, and messing with the input (loose connection) and the thing popped it's caps tops and started flaming..



N.

Replaced even more caps and the thing still decides to smoke.

Maybe I should just buy some new cheapies but I do love a challenge..

Above I've mentioned "input" connector, I mean "power input" not signal..

[mixedgas]

Replaced even more caps and the thing still decides to smoke.

Maybe I should just buy some new cheapies but I do love a challenge..

Above I've mentioned "input" connector, I mean "power input" not signal..

Smoking caps on a LM 22SDA? Check the driver PNPs for shorts/leakage!. The 12V regulator for the position sensors. BTW< you can lift the drive fuses and remove the big transistors and play with just the opamps on a scope till you make sure you have working feedback and position sensors.

Steve

[gashead]

Smoking caps on a LM 22SDA? Check the driver PNPs for shorts/leakage!. The 12V regulator for the position sensors. BTW< you can lift the drive fuses and remove the big transistors and play with just the opamps on a scope till you make sure you have working feedback and position sensors.

Steve

Thanks Steve, you're a star!

I guess I should post pics of the board, by all means it looks *very* similar to the LM22SDA, only slightly different.

Did you have any ideas about the power input connector ?

N.