USB Audio DAC mod + LaserBoy Correction Amp

[drlava]

Andrew;

I don't see how his scanner amps could have been tuned with the DMX board. As far as I'm aware, the DMX board that comes with the ScanPro scanners does not have the ILDA test pattern programmed. (The board I looked at didn't have it anyway...)

I agree, it's unlikely. If switching the polarity and scanner input doesn't help then it's scope time.
Our local industrial surplus has a beaut:
http://www.hgrindustrialsurplus.com/...?id=70-521-315
;-/

[buffo]

Our local industrial surplus has a beaut:
http://www.hgrindustrialsurplus.com/...?id=70-521-315
;-/

Wow! Talk about old-school! Still, for $30 you can't go wrong...

You know, I really need to get a new 'scope. My old one is starting to drift. Maybe I should get in touch with that guy that had all those units from the school - like Alec did. (Wonder if he's got any left?)

Adam

[keeperx]

is that 2 channel and trigger and XY for 30 bucks???

[drlava]

In case you can't tell from the vented top, it's a tube scope. You don't want it unless you have a stock of a lot of tubes.
google HP 122AR to see the tube list in the museum.

[keeperx]

ewwwwww
I got the GoldStar OS-7020a its 20mhz solid state.. no tubes...

[DPSS]

Ok, this is what just happend to me, I hope any of you can make some sense out of it because I'm fealing more and more puzzled each minute .

As suggested by drlava, I checked the cables from the correction amp to the X and Y channels and both signals are going in to the + side, so I tried swapping them at the amps and nothing changed, so then I tried swapping the signals the amps are sending to the galvos, ignoring the stickers they have on them pairing each galvo with it's amp, and VOILA!! a circle appeared, but now the scan angle for both channels is the same as it used to be for the Y channel before I swaped them, which is arround 7 or 8 degrees.

Keeperx,

Thank you very much for the links, I'm going to speak to a fiend of mine that might have an oscilloscope for borowing, but I'll keep an eye on those auctions. I'm not very familiar with what they usually cost, what would be a good price for those two?

Domingo.

[drlava]

As suggested by drlava, I checked the cables from the correction amp to the X and Y channels and both signals are going in to the + side, so I tried swapping them at the amps and nothing changed.

To me, this shows that it's not the DAC, because if it was the DAC, the 'narrowed' axis would have been swapped with the channel swap. But your other test I think again points to tuning. Have you tried other test frames?

[DPSS]

To me, this shows that it's not the DAC, because if it was the DAC, the 'narrowed' axis would have been swapped with the channel swap. But your other test I think again points to tuning. Have you tried other test frames?

I completely agree with you, I think if it was a problem with something setup before the amps, the problem should switch channels when doing so with the amp input cables, and that doesn't happen.

I've tried the Spaghetti patterns and when I switch the inputs the patterns also switch but the scan angles don't. What I can't understand is why, when I switch the galvos at the amps output, the scan angles for both channels sudenly match, could this mean that when they where factory tuned they where conected the other way arround than indicated on the stickers identifying each galvo-amp pair?

And also, is it normal that after setting the pots correctly on the correction amp with the max.wav file and adjusting the USB soundcard's driver settings as explained on page 3 of this thread, I only get a scan angle of arround 7 or 8 degrees?

Domingo.

[drlava]

Only problem I see is that he says that when he connects the scanners to his DMX output board, everything is symmetrical. If that's the case, then the problem is *not* with his scanner amps.

I don't think this is a tuning issue. I think it's a problem with either the volume level on the sound card DAC or a problem with the adjustments on the correction amp.

I've tried the Spaghetti patterns and when I switch the inputs the patterns also switch but the scan angles don't. What I can't understand is why, when I switch the galvos at the amps output, the scan angles for both channels sudenly match, could this mean that when they where factory tuned they where conected the other way arround than indicated on the stickers identifying each galvo-amp pair?

And also, is it normal that after setting the pots correctly on the correction amp with the max.wav file and adjusting the USB soundcard's driver settings as explained on page 3 of this thread, I only get a scan angle of arround 7 or 8 degrees?

This is an odd one. What scanners do you have and where did you get them? I'd be interested to hear what buffo has to say about it with this new information. He's the scanner expert.

That is an abnormally small scan angle even for +/- 5V deflection, but that can be fixed with tuning. After tuning to +/-5V control, don't connect both sides of the differential +/-10V control to the scanners, only connect the + side and ground and you should be fine.

[DPSS]

This is an odd one. What scanners do you have and where did you get them? I'd be interested to hear what buffo has to say about it with this new information. He's the scanner expert.

That is an abnormally small scan angle even for +/- 5V deflection, but that can be fixed with tuning. After tuning to +/-5V control, don't connect both sides of the differential +/-10V control to the scanners, only connect the + side and ground and you should be fine.

My scanners are a pair of Scanpro20's bought through ebay from Dave (Lasershowparts). I'll try contacting him too to see if he can help.

There's something you're saying that makes me doubt if I'm understanding everything correctly. Just to make sure, you talk about +/- 5v deflection, but wouldn't that be for a 3 wire differential connection to the amps that produced -5v to +5v?, I mean, the correction amp produces a 2 wire signal, + and Groung, which generates 0v to +5v, so I've connected the signal cables from each channel on the correction amp to the + input on the amps and the Ground cables for each channel to the Ground inputs on the amps, the - signal cable at the amp inputs is not connected. Is that right?

If what I've just explained is correct and I'm getting it right, let's wait and see what buffo and Dave have to say because, if the scan angle I'm getting is abnormaly small, then there must be something wrong, and I'd prefer to find the problem before trying to correct it makig changes that shouldn't be necessary.

Domingo.