Help! Installing new tube

[Linda Smith Alabama]

Replacing a 60w chinese laser tube. I got the new delivered and ready to swap them out, but have a few questions:

1. is this typical?
There is a slight difference on the output end; In the 1st pic you'll see the cathode where the wire was soldered (old tube.) In the new tube the cathode has a small wire extended out to the water jacket (pic 2.)

2. What is "high voltage tape" and where can I buy it? Radio shack told me they don't carry it. The old tube's power connector was coated with some type of goop (see pic 3.)

3. Does it help to heat the end of the water hose to ease fitting it on the water inlet of the tube? (I broke the old tube trying to remove the hose.)

4. Where's the best place to get new water hose? The old water hose is too small for the new tube.

Thanks in advance for your help!

[Dan Hintz]

It's up to you to solder on a new wire to the metal post. Use high heat and move fast else you will crack the tube. HV tape can be found at your local Borg (Home Depot, Lowes, etc.)... the "goop" is just a fast way of applying a high-voltage sealant.

To put the new water tube on, you can warm it in hot water and use a water-based lubricant (like KY jelly).

[Linda Smith Alabama]

It's up to you to solder on a new wire to the metal post. Use high heat and move fast else you will crack the tube.

Thanks Dan. I realize I have to solder the wire to the post, my question is, is it normal to have the extra wire going to the water jacket? I only ask because the old tube didn't have this. Does this need to be covered?

[Dan Hintz]

Oh, I see what you're talking about... they may have done this for some odd anti-static reason during shipping. Remove it.

[Linda Smith Alabama]

Thanks Dan. I think we're all set to install it tonight.

[Robert Walters]

4. Where's the best place to get new water hose? The old water hose is too small for the new tube.

You could try:
Aquarium supply store
Hydroponics Store
Smallerish Hardware Store.
Medical Supply House


The "goop" is probably something like Corona Dope.
http://www.surplussales.com/Wire-Cable/HVWire-1.html
(scroll to the bottom)

Be sure to use HIGH VOLTAGE rated material, and not something like electrical tape.

[Dan Hintz]

Corona dope, that's the term I couldn't think of...

Go with medical supply tubing, if you can... significantly more supple, and doesn't collapse under vacuum if you get the correct stuff.

[paul mott]

Where's the best place to get new water hose? The old water hose is too small for the new tube.

Don't know if it's any help but I used silicon rubber tube obtained from my local RC model store. It comes in many diameter sizes but for their convenience some come in 1 meter lengths rather than 'off the roll'.

Paul.

[Linda Smith Alabama]

Thanks for the advice. We went to Lowes and got some latex tubing that is working well (very flexible!) This might be the same thing you'd get from medical supply, the employee at Lowes told us it was used in medical field.

We had problems soldering; even with flux it wasn't sticking to the post. So we went with an alternative method I found posted here: http://www.cnczone.com/forums/showthread.php?t=87488 . We bought a terminal strip from Radio Shack and cut the pieces apart. There's a screw-down connection on each end. It was so simple to connect each end and screw it down, then wrapped it with thick self-fusing silicone rubber tape.

[Linda Smith Alabama]

Be sure to use HIGH VOLTAGE rated material, and not something like electrical tape.

This is what we're using; is this considered high-voltage tape?

"Scotch™ Brand 70 Silicone Rubber Electrical Tape is a high-temperature arc and
track-resistant tape composed of self-fusing, inorganic silicone rubber and easy tear and easy-strip liner."

[Robert Walters]

This is what we're using; is this considered high-voltage tape?

"Scotch™ Brand 70 Silicone Rubber Electrical Tape

The datasheet says: "As splice overwrap on spacer cable operating at 15 kV and above. "

It's a bit confusing with the wording they use "overwrap", but it is designed for 15,000 volts at least, which is a good thing =)

How they can say 15KV and ABOVE, is beyond me (probably should have said BELOW, not ABOVE). So could this product be used on a a bazillion volts (I think not).

...terminal strip from Radio Shack and cut the pieces apart...

Um, um, um, *I* have an issue with this...

I'm not saying it's wrong or bad, but hear me out for a moment.

Any terminal strip from RS that you can easily cut apart tells me it's NOT rated for anything over 600V. Laser is probably running in the 8000 - 12000 volt range.

The voltage rating on electrical components is primarily the arcing factor. For example: If you look at any fuse, it has a voltage and amperage rating. This is saying "Once you have exceeded the amperage rating the fuse material will melt and it will not arc (or jump across) the contact points up to the voltage rating"

*IF* one of those screws came loose down the road sometime, it could lead to a poor connection that could cause arcing. I am guessing that you bought the european style terminal strips that are clear/white which are probably PP or PE plastic and could melt or catch fire.

What I might do is completely remove the terminal contact and screws from the plastic housing and use it as-is (if that's possible), then wrap it in a few layers of HV insulation.

I don't know what you were using for a heat source for soldering. But sometimes it helps if you lightly sand the contacts with a very fine grit (400+) sandpaper or emory board (yes, the same as one might use for doing their fingernails) and try to pre-tin each contact ahead of time.

To solder difficult materials, I use a Weller soldering GUN (avoid the Radio Shack version, it's crap),




others like to use a BIG A55 100+Watt soldering iron (notice the 3/8" to 1/2" wide soldering tip on it)