ILT 5405A filament transformer taps

[dash8brj]

very true - and a dumb idea on my part. As kecked said, or an old webcam and have a monitor & webcam app in viewing range. You can buy a new webcam (or probably replaced the junk one anyway), but you can't buy a new eyeball.

Apologies for once being extremly dumb with a laser. And an argon at that - nice pencil thin beam to take my eye out. Stupid. Thanks for the tips on the glass beam splitter etc. I've even got a pass blue/green, reflect red dichro that I could have used.

[dash8brj]

I also forgot to mention, what voltage does the ignite card in these units start firing at? Mine is seeing 330V so if that is too low I may need to move down one tap on the transformer if its not the SCR thats dead. I measured this voltage using the left Cathode voltage test point and the left Anode Current test point.

[kecked]

Scr cheap. Try the other tap

[mixedgas]

I also forgot to mention, what voltage does the ignite card in these units start firing at? Mine is seeing 330V so if that is too low I may need to move down one tap on the transformer if its not the SCR thats dead. I measured this voltage using the left Cathode voltage test point and the left Anode Current test point.

According to the fractional manual I have the switcher generates 380 volts DC static from the AC line before stepping it down to the control the plasma current. Mine (220V version) has 360V of Boost..
I know you need an isolated oscilloscope or some sort of jury rigged LED or something to see this, but are there gate pulses at the SCR ?

Steve

[dash8brj]

I'm too low on boost. My guess is, move the wire to the other tap, try again. If it lights off SCR is fine. If not replace the scr. I am not game to bring my scope near this as it is NOT isolated. I'm used to working with linear supplies, not switchers. Its more than likely 330V is not enough to get the scr trigger pulses happening. I'll move down a tap next time I have it apart. I'm waiting for 2 fans for the side to arrive.

I've discovered the fan wires for local fan configuration inside the head. I need to get cooling sorted before I try again (this was a remote cooled head, which had a plenum on the top for a dryer duct to hook up to, when set up this would lead to a boxed squirrel cage fan that was in the machine the laser came out of). I never received the fan, and would prefer to make it a locally cooled unit anyway. I have ordered the fans and SCR (5 pack for not much more than others want for a single unit). I will be getting an isolated scope soon as I now have two of these things, one working and this one which is needing some TLC. The scope I have chosen is a hantek unit with a built in 4hr lithium battery. That should be isolated enough - no wires to the mains whatsoever. uses ipad as the display screen over wireless.

I can tell I am not getting pulses as there is no "tick tick tick" from the ignitor, and the sacrificial multimeter would be toast by now if it had have been trying to start when I took the measurement

I am in no rush to get this laser going. Take it slow and don't get bitten. Its when you rush and take shortcuts that things go bad and you may end up being bitten.

Thanks for the help kecked & Steve!

[mixedgas]

My pair of ILTS are an Argon / Krypton Pair that run off 220 VAC. I can't do it for a few days due to work schedule, but if you remind me later I can pop the covers and take pictures. The Dip switch settings on the motherboard are complex, and select local/remote control and constant light or constant current mode. Some guy on the other forum (LPF) partially cracked the dip switch code. If you search my posts here you can find a partial remote pinout and the partial internal schematic tied to the remote, which is the only one I've ever seen in the outside world.. If you find his post in "gas lasers" over there, he has a link to my partial drawings, but I think how he interprets the line voltage pinouts in the remote connector is just plain wrong or missing the return signals.
~
One trick for the ignitor is to wind a few turns (1-2) of highly insulated stranded wire in a coil around the SCR low leg, terminate the coil with say 100 ohms, non-inductive, 1 watt, resistor, and look at that with the scope, using a divider across the resistor to get the peak down. . Does the SCR have a reverse diode across it? Those fail a lot. A back termination capacitor to return the ignite pulse to ground should be across the plasma tube some place, either in the head or in the PSU. It will run from anode to cathode, usually are mica or poly film, and be about 0.1 uF. Those fail shorted only when pulsed some times, that happens a lot and shunts the weakened ignite pulse to ground. Also check the head blocking diode, usually something huge in a metal can like an 11RA90 which have a funny habit of testing just fine until they can't block the reverse spike but still work at DC.
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My experience with ILTs has been they rarely die until the tube goes massively low pressure, so I've never dug into mine. If I can take a photo or two that would help you, let me know.
~
Steve

[dash8brj]

Steve: if your talking about vk2fro's post in the gas section, guess who that is, I have that schematic of the remote and did my best to reverse engineer it. Yes that was me. I'd be very pleased to find out the dip switch settings, but from what I saw of dashapples laser, which was running in current mode, and another in light, on off off off is light, off on off off is current

I will have a remote soon, and will be able to properly reverse engineer all the pins, thus giving a proper explanation of what each does, and how to adapt it to a home made remote. I've taken a lot from both forums, its time to give something back. Been helping a few members with their argons, but the ILT supply is quite a complex beast.

The capacitor (back termination) is easy to spot - its at the end of the start card wired directly across the tube. The blocking diode is the biggest diode in the head. Its an MP254 bridge where only one diode is being used, and wired right across the start card output. So you get 4 diodes to play with - if ones shot just move the quick connects to a different diode, observing polarity. The SCR is a 2n6399, a 12A 800V part. The closes I have is a BT151 which is a 500V part. I'm not game to substitute it. I'll buy a replacement for the 2n6399 tomorrow. It, nor does the start card have a reverse diode for the SCR, so thats ruled out. The capacitor checks out fine. It reads 105nF, or 0.1uF. Diode test shows open circuit on it in both directions, so it hasn't died. I found all the required bits to get it up and running at altronics, and will have them friday (thursday in the states). The SCR is not the same model but stats match up or are higher (e.g. its a 1000V part, 16A).

heres a pic of the start PCB:


For now my guess is I simply did not have enough boost. I'll change the tap to match your boost and see if it starts. But I'll wait till I have the side fans first, and all 3 fan wired in. If it starts I'll plop the cover back on (noting that that will open and close the cover interlock so I'll bypass it with a jumper) and let it run at 7-8 amps for a few hours for a maintenance burn, and while its running, tweak the mirrors for maximum power.

A quick question: the small transformer in the supply that isn't switched by the SSR is to power the head fans, and hour meter correct? if thats the case I can move its tap to 240 on that one, to power the fans. Steve in order to assist, you don't need to open your head, but check the voltage rating on the fans. If they're 220/240v, open up your psu and look to see where the blue wire is connected on the transformer (it will be labelled with a voltage rating). The other wire I need you to look at is the grey one going to the SSR card on the front of the PSU. That should lead to the filament transformer.

edit: Ok I have scored quite cheaply off ebay the 240V version. So Steve there is no need for you to go ripping into your PSU to check transformer taps. I'll modify the 210V version to follow the same wiring scheme as the 240V version and they should both then work off 240.

I will of course note my modifications so anybody finding this thread can duplicate my modifications to get their supply running off 240, or change a 240 to run off 220.

[dash8brj]

Well my RPC 50 rocked up. Looks clean inside, no blown up parts so that has to be a good thing I haven't powered the system up yet (waiting for the 240V supply) but Steve a lil question, do I need to change any dip switches to enable remote control of the laser via the RPC 50?

I know I'll need to recalibrate it as they sent me the 0-50mW version instead of the 0-600mW one, but thats easily fixed - adjust the trimmer for the light control, diverting more voltage to ground to attenuate the scale. Then I can simply put a nice lil sticker on the panel "x10"

[mixedgas]

I opened mine to find a cathode transformer as expected, and a boost transformer, connected on the primary with just two terminals, no taps. It never ceases to amaze me what all the seemingly useless variations are in Ion laser Power Supplies, even of the same model number. Sorry, I'm of no help...

Steve

[dash8brj]

Stupid eh? mine has two transformer (4 in total) on the base plate - obviously the filament transformer is the big one, then a smaller one with taps written from 115-240V, then theres a 220-115v one wired back to front (220 on the 115 input) on the ham pcb (think of the 3 pcbs as a ham sandwich- the middle one is the slice of ham), then theres a fourth on the interlock board, screwed onto the solid state relay. That one was already jumpered for 220.

heres a picture of the guts:



you can just make out the 3 transformers up front. first (going anticlockwise) is the interlock board, second is the filament, third is the small transformer, which probably runs the fans, rpc 50 (if connected) and hour meter. The fourth, hidden from view under the logic board, is the boost transformer.