Omnichrome HeCd Laser - need help....NOW FIXED!!!

[timelablasers]

Hi all,
I have an Omnichrome HeCd laser. Laser head is a Series 56 and the power supply is an LC-500. When I press the 'on' button button, I get the red light blinking three times repeatedly after the self test. This means 'filament current error'. Sam from Sam's FAQs sent me some documentation to test a whole lot of resistances between pins on the head and they all came back within limits. Is there any way to override the self test or trick it that the filament current os ok? I'd really love to get this laser going to add it to my collection. Can someone please give me any hints?
Thanks heaps.
Rob.

 

[Cyparagon]

Re: Omnichrome HeCd Laser - need help

I think Gus fell off the face of the earth. He's the only one I know of that's had a HeCd. Diachi maybe? Otherwise I'd recommend photon lexicon.

 

[diachi]

Re: Omnichrome HeCd Laser - need help

Hi all,
I have an Omnichrome HeCd laser. Laser head is a Series 56 and the power supply is an LC-500. When I press the 'on' button button, I get the red light blinking three times repeatedly after the self test. This means 'filament current error'. Sam from Sam's FAQs sent me some documentation to test a whole lot of resistances between pins on the head and they all came back within limits. Is there any way to override the self test or trick it that the filament current os ok? I'd really love to get this laser going to add it to my collection. Can someone please give me any hints?
Thanks heaps.
Rob.

Do not fear! Help is here!! :san:

Model 56 - Smaller version of the model 74. Sealed Mirror tube - Mutlimode with a quartz bore I believe.

I'm not familliar with that powersupply, but it sounds to me like an open cathode filament.

If you go inside the head with the powersupply DISCONNECTED you should see three pins at the output end of the tube, one is neutral the others are live. Those HeCds had two Filaments, a main one and a backup one incase the main failed. Actually ... a lot of "hot cathode" HeCds had this feature.

I'll dig out a drawing so you can see what pins I mean.

!!DO NOT PRESS THE RED BUTTON ON THE SIDE OF THE HEAD - THIS IS A LAST RESORT FOR A DYING TUBE - INCEASES TUBE CURRENT,CADMIUM RESERVOIR TEMP. AND HELIUM PRESSURE - remelts the cadmium in the cadmium condenser. !!
^^ I actually heard tell of a guy remelting the cadmium from the cadmium condenser and running it back down the bore to the original cadmium reservoir - it worked too for a while - until the cadmium condensed in the bore which killed the laser.

!!DO NOT TURN THE LASER OFF WITHOUT GOING THROUGH THE COOLDOWN CYCLE!!
^^Cadmium will condense in the bore leading to a rather dead laser - it can sometimes be revived, but not always. This can also lead to problems with the tube in the future if it is shut down without the cooldown cycle frequently.

!!DO NOT ADJUST THE HELIUM SET VOLTS/HELIUM PRESSURE REFERENCE!!

 

[diachi]

Re: Omnichrome HeCd Laser - need help

I think Gus fell off the face of the earth. He's the only one I know of that's had a HeCd. Diachi maybe? Otherwise I'd recomment photon lexicon.

GooeyGus may be caught up with life at the moment, he had a death in his family recently and he probably has a lot on with Family/Work/Christmas.

*note to self - update signature.*

 

[diachi]

Re: Omnichrome HeCd Laser - need help

That should help ya

*Tripple post ... I know - getting used to being allowed to do it over on PL *

As I said before, I'm not familliar with that model PSU - mines had the model 100-B ... or was it C ... Hmmm ... anyway, my best guess is that the cathode filament circuit is open SOMEWHERE along the lines, that or it's a sensor fault, but that seems less likely. Test for it as I said above by measuring the filament resistance on both filaments, at least one should read a near dead short. If you don't have a DMM , get a cheap one. You don't need to be accurate so long as you can tell if it's open or not.

How many hours does the meter on the side near the red button indicate?

Actually ... does your head have the test panel on the back of the head? Can you get me some pictures? I know the tube construction is the way I think it is - that is for sure. models 39,56 and 74 are all just the same tube but different lengths, 39 = 39cm, 56=56cm and so on a 112 series head is two 56 series tubes together in series. I'm not sure on any differences in the case construction between the heads. The red button and hour meter should be beside the testpoints on the head anyway.

Cadmium pressure is monitored by tube voltage, tube voltage can also be changed by changing the cadmium pressure.

-----------------------------------------------------------------------------------------------------------------

Hope this information helps, I know you didn't ask for it all - but I thought I'd part with this information anyway. You may need it in the future.

 

[timelablasers]

Re: Omnichrome HeCd Laser - need help

Hi diachi,
Thanks heaps for your help with this. I'll check it out today and get back to you. If the spare already connected or does it need to be rewired to use the spare?
All the best,
Rob.

 

[timelablasers]

Re: Omnichrome HeCd Laser - need help

I've found the cathode wires, one black two yellow. One of the yellows was not connected to anything so I assume that is the spare. Tested continuity and both have basically 0 ohm. Changed over to spare anyway and no difference. I can also see a orange glow inside the tube when the power is on so I assume the filament is intact.
This is going to be fun....
Where to from here do you think?
Thanks again,
Rob.

 

[diachi]

Re: Omnichrome HeCd Laser - need help

I've found the cathode wires, one black two yellow. One of the yellows was not connected to anything so I assume that is the spare. Tested continuity and both have basically 0 ohm. Changed over to spare anyway and no difference. I can also see a orange glow inside the tube when the power is on so I assume the filament is intact.
This is going to be fun....
Where to from here do you think?
Thanks again,
Rob.

Filament is not only intact, it is lit. Unless it's going overcurrent ... but I doubt it - have you got the schematics for that PSU? I'll have a look at them and see what I can see. Sounds now like an interlock or sensor. Have you got the head interlock in? it should be a lead coming from the umbilical cable with a two pin female connector. Those two pins need to be shorted.



E-mail me : what_if_93 (at) hotmail.com

 

[timelablasers]

Re: Omnichrome HeCd Laser - need help

Hey there diachi,
I don't have any schematics for it. The umbilical has only two plugs at each end, one for HV the other low voltages. No interlock connector as you suggested. I will take some photos tomorrow and post them here for you to see them. That might make it easier.
Thanks again for all your time and help.
Cheers,
Rob.

 

[diachi]

Re: Omnichrome HeCd Laser - need help

Hey there diachi,
I don't have any schematics for it. The umbilical has only two plugs at each end, one for HV the other low voltages. No interlock connector as you suggested. I will take some photos tomorrow and post them here for you to see them. That might make it easier.
Thanks again for all your time and help.
Cheers,
Rob.

that'll help a lot

 

[timelablasers]

Re: Omnichrome HeCd Laser - need help

Hi diachi,
Here are some photos of the HeCd laser. I removed the counter from the front of the head to make the wiring more visible.

I hope you can see some clues as to what might be wrong, because I sure can't
:thanks:

 

[diachi]

Re: Omnichrome HeCd Laser - need help

Looks like you've got a more modern version! My 74 was made in 93.

Head is completely different, although the tube construction is identical. Everything looks to be physically in great condition.

Where is the LED that says Filament over current? I can't seem to find it in the pictures.

Have you got the correct line voltage? If that's too high then that could cause a filament over current warning to arrise.

Your filament is lit so it doesn't seem that it's not getting enough current ... it looks like either too much, or a problem with some of the sensor circuitry in the PSU/Head.

How long have you left it on for? I know sometimes the He Heater LED on mines would stay on for about 10-15 seconds at startup. Maybe it's just doing that?

 

[timelablasers]

Re: Omnichrome HeCd Laser - need help

Hi diachi,
There's no LED for filament over current. The error LED just flashed 3 times meaning that its a 'filament current error', according to the error documentation I have. Very vague I know. I've got 240 VAC running into it. Do you think I should try it on 110?
I've left it on for a few minutes trying to restart it but no joy. If there's something wrong in the PSU, well that's gonna be fun to find.
Let me know if you need more info.
Thanks heaps.

 

[diachi]

Re: Omnichrome HeCd Laser - need help

Hi diachi,
There's no LED for filament over current. The error LED just flashed 3 times meaning that its a 'filament current error', according to the error documentation I have. Very vague I know. I've got 240 VAC running into it. Do you think I should try it on 110?
I've left it on for a few minutes trying to restart it but no joy. If there's something wrong in the PSU, well that's gonna be fun to find.
Let me know if you need more info.
Thanks heaps.

Is there a switch anywhere ( Like on the back of a computer ) to set it to 240V/110V ? If you want to try it on 110V you're gonna need a fairly large transformer - I think mines too 10A or so off of my 240V line, so that's 2.4kW ...

If you had a schematic this would be easier, you could trace back the filament leads into the PSU and check that part ... these PSUs are VERY complex

Without a schematic I can't help much more - PL is now your best option - Steve ( Mixedgas ) will be able to help - he's the gas guru. You might also be able to find a PSU for that large HeNe of yours over there.

 

[Cyparagon]

Re: Omnichrome HeCd Laser - need help

2.4KW without heatsinks?? What's a more nominal current draw?

 

[Experimentonomen]

Re: Omnichrome HeCd Laser - need help

That is one overly complicated switchmode power supply!!

As it have led´s for error codes its likely microprocessor controlled, and then fixing it is likely as good as impossible.

Sorry mate.