Modifying Q-switch driver for external modulation

[weartronics]

Hi PL,

I found that many Laserscopes have Crystal Technologies 1027-25 driver inside. Thanks to Dave at Lasershowparts I have a data sheet for this, but no manual. It looks like these were probably OEM for Laserscope, with some internl pulse generator (there is no obvious modulation input).

Does anybody have a manual for this model they could send me? Does anybody know if there is an extra card available for external modulation? Has anybody modified this driver for external modulation with FPS before?





Best regards,

weartronics

[shrad]

just a piece of advice, the connector laballed J501 or so seems to be pretty close to the optocouplers, and this part of the board could be a TTL modulated clock source for the RF amplifier

do you have any info on the connector use?

if no one knows about modulating this, it might help to know each of the IC's references, for people to determine what kind of oscillator design this is (PLL or so)... knowing that, it might be possible to modulate the beast, as the usual design is relatively close to any FM modulator

[mixedgas]

DANGER WILL ROBINSON.

I have one of those in my new greenie, too.

NOT rated for blanking for more then a minute, some RF part of them cooks itself.

My medical tech friend was VERY CLEAR, do not use them for prolonged hold-off. He's fried a few as part of a alignment procedure.

Since I dont see a doubly balenced modulator can in your photo, I assume they are switching the bias to keep costs down. This is fine if your pulsing it, but not so good for prolonged hold off, which makes me think it would be whatever switches the bias that blows. I have not taken the lid off mine yet,and am a few days and need to find a big honking 24V power supply before trying it.

The coolent pump in my Emerald Focus laser is also 24 volts.

Its one enable, and one pulsed input on that little multi pin connector.

I have a schematic in the piling system for the inputs. Looking at it, its a off the shelf motorola RF amp design from a APP note, the big honking transistor there switches the bias to the amp, in effect modulating the RF.

Steve

[shrad]

Steve, with your competences, have you ever tried to drive AO devices with a FM modulator?

we had a meeting one month ago in france where a friend demonstrated that any mid-powered FM emitter was able to modulate an AO device (the thing is just to match the device central frequency), and it worked! that was just a 1W FM transmitter hooked to an isomet

I'd like to experiment this way, and I'll have a look for cheap AO devices to play with... not right now though, as I'll sign a buy act for my first house this evening ^^

[mixedgas]

VHF is not rocket science, you can build a AO driver for about 20-40$ depending on how well you scrounge and ebay. Yeah, I've done that.
all you have to do is be careful not to overdrive.

here is how you get your AM to turn the beam on and off.

http://www.minicircuits.com/cgi-bin/...arch_type=info

A lot of mixers have a DC IF, so you pump in 5-7 mA into the IF port and they become a RF switch or a amplitude modulator.
level 7 mixers show up on EBAY

Here is a cheap to build amp:

http://www.techlib.com/files/class_c.pdf

heatsink it and keep lead lengths short.


Those coil values are easy enough to wind by hand out of scrap #14 house wire or some #22 on a ferrite bead.

here is how you measure whats going on.


http://www.techlib.com/files/detect.pdf (put a 50 ohm metal film resistor or a 50 ohm 1206 SMD resistor in as a load)

four 200 Ohm resistors in parallel make a nice dummy load to practice on. Build on a copper ground plane, dead bug style.
Build all of this stuff on copper with as short a lead as possible.

You really only need 250 mW or 500 mW max for most modulators.
Much more then spec fries the tiny bond wires.

Digikey clock in the cans TTL oscillators are often within a few mhz of where you need to be, most modulators are 10-20 mhz wide. You can AC couple them to the RF amp or DBM using a .1 uf or so ceramic cap. You may need more then 1 RF amp to get from the clock to enough power, thats OK, they can go in series.

I use these things they show up a lot at hamfests and ebay, and the forward ones have more power then the reverse ones. Often show up for 5$ when cable companies upgrade. Sometimes cable repair places can find them for you in their scrap bin for the asking

http://www.acronymeo.com/phbg200mh24d.html

these help you set levels, although at vhf you really just want to use three resistors

http://www.nt7s.com/index.php5?page=stepatt

I've built the Wenzel amp, it works, and he wrote the RF with DVM thing back when I asked him for help as I had no RF test instruments back in 2000., so I know the RF with VOM thing works good. That is so nobody accuses me of googling all this.

This works for the RF "Greek" when learning dBm

http://www.minicircuits.com/pages/pd...NV%20TABLE.pdf

108 to 139 is the VHF aircraft band, so unless you like visits from the FAA/FCC , please shield anything you build in that range in a metal box.


When I get done with my backlog of files to post, I'll scan in a xerox AO amp, circuit wise its almost a joke, easy to clone.
Steve the "RF CHEAPSKATE"

[shrad]

wow! nice post there!

thank you for these resources

[buffo]

I'll sign a buy act for my first house this evening ^^

Congrats on the new home purchase!

Adam

[shrad]

thanks this is a quick pick, a golden deal, if everything goes well I'm moving in 2 months will have a barn to store lasers

[weartronics]

I should add, in case anybody is interested, I found the original manual for this Q-switch driver!

http://external.weartronics.com/aoqs...er_1027-25.pdf

Best regards,

weartronics

[aijii]

hmm..

manual states 6 - 12khz rep rate...

but elsewhere i've seen Laserman quote a minimum rep rate of 10khz, all the way to 25khz ?