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ALC909Z ZPS.02 Magnet Question
Hello all,
I'm working on getting my ALC909Z up and running, and had a question regarding the magnet.
My ZPS.02 had some issues after sitting on a shelf for nearly a decade. All of the electrolytic caps on the input board and one in the driver section had leaked. Installed new caps and got the PSU working again.
Wired up the head and lit it for a few seconds to test everything. So far, so good.
My question is regarding the magnet. Resistance measurement is about 50 ohms. When I place the magnet across the ZPS output, the PSU appears to go into some sort of protection mode. The voltage across the caps starts to ramp up quickly when I bring the HV EN lines high, as I'd expect, but then after about five seconds, the output falls off. Trying to light the tube while the magnet is across the PSU fails.
Without the magnet, everything is working as expected, but I've only ran it for a few very brief test runs in this configuration, as I don't want to damage by running it without a magnet for any length of time.
Would anyone happen to have any insight into what I'm doing wrong with the magnet wiring?
I could put together a variable supply for the magnet. Have a variac laying around, as well as caps and bridge rectifier. If I go this route, what voltage is recommended?
Thank you,
Brad
Last edited by bradstockdale; 04-26-2017 at 06:20.
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I ended up rigging up a variable DC power supply out of a spare variac, an IR bridge rectifier, and five 1,000 uF 350VDC electrolytics out of an old fluoroscope.
I pushed about three amps into the magnet. The resulting change in power output of the 909Z is amazing.
While it's not as self contained as running it off the ZPS, I can't beat the outcome obtained by using junk box parts.
Time to clean the entire system up, make it safe, and add permanent metering, now that it's all proven out.
Thanks,
Brad
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Can you post some pictures of the laser interior and output?
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Surely. Here's one I snapped last night while testing the magnet PSU. I'll take some more tonight. Please don't mind the mess; I wanted to get everything working before I put more effort into tidying everything up.
Bad idea to use a paper target. After snapping the photo, I had to deal with a burning piece of paper. Time for a more appropriate beam stop.
Last edited by bradstockdale; 04-27-2017 at 01:25.
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Thank you. I never get tired of seeing a working argon laser.
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Awww! It's tiny! And so clean too!
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I haven't forgotten about more pics. Been a busy week. I'll take some in the next few days. Kinda hate to show how messy the wiring is, but it is what it is for the moment.
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I see a couple spare Lexels on the bench behind your 909. Might want to measure the resistance across the magnet of one of those 75's and see how it compares with the 50 ohms you reported on your 909. To me that sounds suspiciously high...
Adam
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Adam,
Good idea. I have another 75 (for parts) in another building. I'll measure that one this week, out of curiosity. I have a contact overseas that has been working with medical 909's for years. I had pinged them at the outset of bringing this 909Z back to life, They measured the resistance of their magnet, and came up close to 50 ohms as well. I'm hoping that the correlation means that this is valid. I've also been told that about five amps is the appropriate amount of current for these. But. my variac is only a 120 model, so even using the boost taps on it, I can only eek out about 150VAC, which when rectified, filtered, and applied to the magnet, is about 2.9 amps. I'll report back on the 75 magnet resistance.
Here's another photo of this head:
Poor attempt to see the lines:
Low power:
Higher power:
Thanks,
Brad
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Sick!
At one stage I had one of these :-) running off a lexel88 oem switcher, they have a bit of get up and go! Iirc, 3.5w all lines at about 25A tube current
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