ALC-68 / Meditec EIL-4000, Help needed please

[Bastiaan]

Hello everybody,

Recently i bought a non-functional air cooled argon laser system for not to much money. I am trying to get the laser working, but i realy need some help on this guys.

These are the specifications:

Laser: American Laser Corporation
Type: 68C / 5.95 Watts / Argon / 457 - 514
Voltage: 220 V.
Amperage: 60 A.

Power Supply: Meditec EIL-4000 (wired on 1x 220V phase)

When i opened the 19" case of the power supply, the first thing i noticed is that there is some home build expriment board on the back. The components are a 220v <-> 15V trafo, 7812 voltage regulator, 555 Timer a transistor and some caps. 2 Wires of the board are connected to a relais. As you can see in the pictures below there is a empty IC socket, but it isn't connected to the schematic, it is just there. So i know for sure this IC socket has no function, I guess this is some sort of startup delay circuit ?

The laser itselfs has no visual damage for as far as i can see. I carefully tried to power on the laser, when i switch on the power supply the build in fan is rotating and lights on the front lights up. Also the 2 fans on the laserheads starts rotating. I think the front panel of the power supply is modified, it has a 2 way switch for I and V, and a potentiometer with a build in switch at the lowest position. When i set the 2 way switch to V the meter is showing 40 Amps. I guess the V stands for Volt and the I for Current? I tried to turn up the potentiometer slightly to see if something happens, but the laser won't turn on. At this point i stoped expirimenting, and realy wanted to ask you guys if you can point me in the right direction how to power this thing up without damaging it.

Tonight i am gonna check al the fuses in the power supply and laser head. The guy who made the modification is very unprofessional, so im thinking of pulling out his timer board (on the back) and restore the wires for descent ones.


I Have a couple of questions:

- What is the home made circuit on the back?
- How to determine what is wrong with the laser?
- Does anybody have a schematic or pin wiring of the Meditec EIL-4000 powersupply and/or this laser head?

Any information on this laser is more then welcome.

Thanks for your time!

Best Regards,

Bastiaan

[mixedgas]

I have meditech schematics in my file system.

It will take me a few days to compile them.

Due to how critically the low cost meditech PWM board runs the switcher, it is ILL ADVISED to attempt to run it without the schematics.
It can oscillate and kill the tube or power supply or BOTH if the feedback circuit is not wired correctly.

You can easily ruin the passbank transistors if it is not set up or controlled correctly.

The thing on the back must be a 30 second delay for the cathode to heat up.

I is the amp meter setting. V is the tube voltage setting. V only means something if the tube is lit and ran at a specific current.

As the meditech can be wired for a variety of head wiring schemes including series magnet and parallel magnet, it is AGAIN ILL ADVISED to attempt to run it without diagrams. Especially since that is NOT the factory wiring harness. Please wait till I can get some data scanned in.

If it is reading on the amps scale without the tube running, something is already badly wrong.

Dont pull his board until you see how it it is wired into the controls. Meditech used external feedback and light sensors to control the tube current. The PSU itself is rather DUMB, it it will not protect itself. It can be configured many, many ways, and only one will work for you. Until you see how that is wired in, leave it alone.

I work a 12 hour day, so this will take me some time.


Steve

[Bastiaan]

Thank you so much Steven, i realy aprieciate your help. Please don't hurry, take your time

Like i said, i powered on the PSU for like 5 seconds. I didn't notice any amps reading then. I will not power the laser on till further instructions. In the mainwhile i will make a drawing of the wiring as it is now. Also i will check the fuses and try to repair the "Netz-Ein" lamp on the front of the PSU.

The power supply is now housed in a terrible wooden box. No electronic device should be in this kind of housing. So i will try to clean things up and get a good overview of all the parts and connections.

Is it safe to measure the cables between the PSU and Laser with an Ohm meter (ofcourse with PSU turned of)? I have seen the caps inside the PSU, i don't want these guys to discharge on me. All the wires inside the multicable between the PSU and Laser are colored black, so i need to measure to find out what is what and make a schematic on paper.

Again thank you very much steven!

Best regards,

Bastiaan

[mixedgas]

Take a look at the head. Some times they used the ALC boards, some times the used meditech boards. Meditech boards are tiny little squares. ALC boards are bigger and much better made. Please post the inside the head pictures.

The head should have 4 electromagnets. How they are wired matters, as far as series/ parallel / half series and half parallel. All three combinations are known to exist.
Polarity somewhat matters on the magents.

Steve

[Bastiaan]

Hi Steve,

I quickly made some pictures of the head this morning before i go to work. Also i measured the 5 glass fuses inside the laserhead, they are all OK.

Please let me know if you need more detailed pictures.

Bastiaan

[smogthemog]

I have just purchased another ALC68, actually marked as an 80! so we can possibly work together to get these beast running
Steve is THE MAN when it comes to these so listen to him rigidly and you will not go wrong!
Hope it's up and running soon.

Have you seen my old thread where I renovated on of these? Do a search.
Jim

[mixedgas]

Yeah, yeah, yeah Smog, someplace I have a schematic of the ALC psu as well.

They are burried in a big pile at home. That way all I have to do is light the bonfire to clean house.

Steve

[tonyaztec]

These may be of some help guy's, from when I had my 68

[mixedgas]

Tony's Asculap/Meditech output schematic is the correct one for the Meditech PSU, but it does not cover the current potentiometer modifications. The Meditech supply is a ALC clone but uses a much different current control card and wiring harness then the one in the ALC internal schematic.

Steve

[tonyaztec]

Steve,

I have somewhere on email some info sent to me from Adam (300evil) regarding the the current potentiometer modifications. I will try and find them later.

Tony