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Author Topic: Welder as rectifier Colin Penny Film Handler Posts: 9 From: sydney mines, ns , canada Registered: Sep 2019 posted 10-04-2019 02:43 AM                     Anyone running a welder to lower their lamp. If so can you show how you have it wired and what components you used to smooth it. Thanks  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-04-2019 07:09 AM                     It has been done there were several rectifiers that were modified Hobart welders But they would require filtering and a boost supply Not for the faint of heart  |  IP: Logged Jim Cassedy Phenomenal Film Handler Posts: 1661 From: San Francisco, CA Registered: Dec 2006 posted 10-04-2019 07:53 AM                     I beleive this topic has been covered once or twice before on this forum. I was able to find one thread HERE But I seem to recall seeing one that also had some pictures. The big 'issues' you'll have to deal with are: 1) Duty Cycle 2) Ripple Filtering 2) Coming up with a way of dealing with Xenon starting pulse. On the other hand, I have seen a rectifier used as a welder, when I once dropped a pair of metal pliers into one & it welded them shut!  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 10-04-2019 10:13 AM                     If you have a Strong lamphouse with the AC ignitor, possibly you can just hook up a DC welder and hit the manual strike button. You will likely need some extra filtering, and some hefty capacitors to provide starting current. I don't know how much an inverter welder would like a lamp load. The IMAX 15-20kW Millers were "brute force" types with massive transformer and choke. A boost voltage was added but I don't know if that's needed to strike a lamp or just tells the lamphouse that the rectifier is on and triggers an autostrike circuit. The added front panel box was mostly tamperproofing so the power switches couldn't be fiddled with: switching it to "ON" would disable power control from the projector and if you shut down the IMAX system the lamp would stay on... boiling off the internal coolant pretty fast then melting the cathode electrode seal and exploding the lamp when coolant leaks out inside the white hot envelope. Fun times.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 10-04-2019 07:53 PM                        switching it to "ON" would disable power control from the projector and if you shut down the IMAX system the lamp would stay on... boiling off the internal coolant pretty fast then melting the cathode electrode seal and exploding the lamp when coolant leaks out inside the white hot envelope. Fun times. Hot DAMN, Dave, I would pay a bucket load of money to see that! It sure would make a great documentary...the dangers of tinking with stuff that you shouldn't. And heck, there certainly are enough mothballed IMAX projectors sitting around that no one would miss an exploded one, eh?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 10-05-2019 12:37 PM                     Boost voltage is required to start a lamp The sequence is The boost supply charges the out put capacitor to (depending on vintage) up to 150VDC This serves to purposes one to trigger the ignitor circuit and Two to provide a large inrush current to establish the current flow ( too much inrush will also damage the electrodes too little the lamp will just go out) I high voltage around 50KV and approx 30Mhz is superimposed by the ignitor to ionize the gas in the lamp and to create the electron path between the two electrodes. This is in serries with the lamp so a bypass capacitor is required across the rectifier It has to decouple as soon as the arc is established and then the main rectifier provides depending on the lamp the high current low voltage  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 10-06-2019 12:35 AM                     quote: Dave Macaulay The added front panel box was mostly tamperproofing so the power switches couldn't be fiddled with: switching it to "ON" would disable power control from the projector and if you shut down the IMAX system the lamp would stay on... boiling off the internal coolant pretty fast then melting the cathode electrode seal and exploding the lamp when coolant leaks out inside the white hot envelope. Fun times. Geordi La Forge to Bridge: Captain: We have a coolant leak in the projector's core. I'm trying to stabilize it. 10 seconds later... Geordi La Forge to Bridge: The core's cathode electrode seal is melting, the coolant is boiling off at a very high rate. I can't stabilize it. Captain Picard to La Forge: Eject the IMAX Core! Geordi La Forge to Bridge: IMAX Core ejection systems are off-line! Captain Picard: All hands abandon ship! Repeat, All hands abandon... Sorry, it was a long night.  |  IP: Logged

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