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HeNe PS woes..[solved] photo update:JDSU 1135P dissection/decanned

Down with Umbrella

Down with Umbrella

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Re: HeNe power supply wiring connection woes..

Upon further investigation I found this. Fried.

I'm quite sure this didn't happen the other day because there was no smoke, nothing hot, no smell. This must have happen before I even got it. I know there is some potting in these heads but I doubt the whole cap would melt.

I'm going in deeper....
 





hwang21

hwang21

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Re: HeNe power supply wiring connection woes..

Usually that cap just has the ballast resistor in it. It shouldn't be difficult to fix that- I liked to bare tube my lasers, and I just cut the wires to the potted cap and reran the ballast resistor and wiring. Simple

Although that HR lens doesn't look so good
 
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Down with Umbrella

Down with Umbrella

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Re: HeNe power supply wiring connection woes..

Yeah, I see the Ballast resistor 75k ohm. I might replace that, de can the tube, than clean up some of the wiring and try that. It might be completely shot but I have time and I want to check it out.
There is also a resistor in the front cap behind the snap ring. I don't recall that resistor color coding. I can check when I get back to the house.

A project I'm working on requires a decanned HeNe that does at least 7-10mW so learning to do this is needed.
 
icecruncher

icecruncher

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Re: HeNe power supply wiring connection woes..

Down with Umbrella said:
Yeah, I see the Ballast resistor 75k ohm. I might replace that, de can the tube, than clean up some of the wiring and try that. It might be completely shot but I have time and I want to check it out.
There is also a resistor in the front cap behind the snap ring. I don't recall that resistor color coding. I can check when I get back to the house.

A project I'm working on requires a decanned HeNe that does at least 7-10mW so learning to do this is needed.
Click to expand...

Be careful

Usually lots of glue and easy to get frustrated :)

Hopefully its just that ballast resistor!
 
Down with Umbrella

Down with Umbrella

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I updated the OP with all the details and photos.. Check out my days work. Hmm :undecided:
 
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Down with Umbrella

Down with Umbrella

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icecruncher said:
Very nicely done.

Hope it will work for you.
Click to expand...

Thanks icecrusher, I briefly tried it. The tube flickered a few times when I cycled the power on and off. It's still missing a Ballast resistor. It flickered but never stayed lit. I might try cleaning the dirty connections once I feel the tube is bled off.

It's also possible the ps doesn't have enought starting voltage for the old and battered head As stated above.
 
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ultimatekaiser

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Well It can't run without the ballast resistor. The tube is a negative resistance device so without it to limit the current it will always flicker. As long as it's flashing orange it should be fine, you can buy a 75K 5 watt resistor and that's probably enough, though for some added stability if you really want you can add a 10K to the other side, but that shouldn't be necessary if it's out of the cylinder, since the capacitance of the tube will be a little lower out of it. If it's flashing then the starting voltage is low enough, you just need to have the ballast within 3 inches of the anode to stabilize it.
 
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ultimatekaiser

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Sounds good to me, though honestly you probably don't need the 10K out of the cylinder, it's just to help stabilize it in the cylinder. Outside of the cylinder you're pretty much just increasing the voltage needed to run it, not that it hurts to have it there, I have a 10K on my test Alden cathode wire.
 
icecruncher

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Thinking the same thing on regarding missing ballast resistor

If you are getting flashes as long as the mirrors are OK, you should be golden.
 
Sigurthr

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Fyi, if you have black crud left on the tube it can usually be removed with 91% isopropyl alcohol. Some potting compounds require thermal degradation before they become soluble, so what I've done in the past is put the oven on to 300F and place the tube in a cold oven, let it bake for about an hour, let it cool down, and then scrub with terrycloth soaked in the IPA to clean the tube up.
 
Down with Umbrella

Down with Umbrella

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I have some Everclear on top of the fridge for cleaning things of this nature. My roommates won't dare drink it so that's good. Steam worked pretty well for taking the goo off.

Question: how are the mirrors attached? Is it an epoxy? The other resistor took damaged on the way out so I have a new one coming.
If I were to shake the tube carefully there is no rattle so that's good. I'll be happy if at the end of this I have a cool plasma tube.
I appreciate the feed back!
 
ultimatekaiser

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That would be okay as long as the temperature transitions are slow enough it doesn't crack the tube. And so long as the getter hasn't absorbed a significant amount of contamination. most of that RTV stuff comes off pretty easy if you just lightly scrape it and then rub it off... Alcohol and hydrogen peroxide usually make it go faster.

Edit: The mirrors are sealed on with frit, which is basically like a low temperature solder for glass. It won't dissolve or come off easily. Though if you whack the mirrors the wrong way or stress the seals they could pop off.
 
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Sigurthr

Sigurthr

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To augment UK's data about the frit; it does have a significantly different thermal expansion coefficient than the glass and metal, and a mere 500F is enough to cause tube failure. I discovered this the hard way on a tube that no longer lased (plasma deposition damaged the OC) that I turned into a plasma lamp with about 300W of RF.

Running nearly-happly at 300W.
MdJ4NX1.jpg


Nearly up to air after the frit expanded causing a crack.
6MbLx65.jpg
 
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