HeNe Power Supply issue

I doubt the tube is damaged if you're seeing any laser beam come out at all. It is still very possible it needs more ballast resistance. I don't know why it would suddenly need more ballasting when removed from the housing unless it used two resistors and you only found one. That would make the most sense as I said earlier 35k is VERY low. 68k is typical and two 35k's in series would probably work fine. This PSU seems to supply 4.0-5.5mA which should be perfect for most of these tubes. I'd set the pot to the middle of the range.

If you can run to a radioshack or equivalent and grab a 68kohm resistor. The more wattage the better but I've used 1/4W before. Try it instead of the ballast resistor you are using, it might just solve all the issues.

Just double checked and there is nothing else In the end piece. It will have to be thursday when I can get to radio shack. Going too high wont cause any damage will it? Should I buy an areay of resistors and just slowing increase resistance untill it works or jump right tp the 68k?

Too high wont cause any damage at all. Grab a 68k and a bunch of 10ks, then you can try in 10k increments if you like. My money is on 68k though.. I've ballasted over 10 tubes of varying sizes with 68k.

Bear in mind the capacitive properties of the metal enclosure and its effect on the discharge down the bore.

Speedy78 said:

Just double checked and there is nothing else In the end piece. It will have to be thursday when I can get to radio shack. Going too high wont cause any damage will it? Should I buy an areay of resistors and just slowing increase resistance untill it works or jump right tp the 68k?

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Just being thorough here --
You are already getting very good help

In the endcap, it there any rubbery or plastic looking substance?
Often times resistors are "buried" in material in the cap

Peace,
dave

When I pulled the wire out I could see where it was connected to the inpyt from the outside then followed it to the back of the tube. Thats when I cut the resistor out to facilitate taking that tube out. So its just this 1 resistor. I even double checked. Only thinh left is what apears to be something reflective inside a black llastic tube that was inline with the back mirror. It has two wires coming out of it. They were never hooked to anything before. I think it was something to monitor ouput.

phenol said:

Bear in mind the capacitive properties of the metal enclosure and its effect on the discharge down the bore.

Click to expand...

Just saw this. Should I be adding a capcitor of some sort then?

No, try with bigger ballast or put the tube back inside.

Success!! Well sort of. Radio Shack didnt have anything close to what I needed. All their high wattage resistors were a mere 10 ohms. All they had was 1/2 watt in anything I could use. Did some quick math and have 5 470kOhm and 1 220kOhm resistors in parallel giving me 65k measure on the DMM. Am I correct in thinking all these half watts in parallel give me a 3W resistor? Any way tube fired up like it should. No more buzzing and a nice stead glow!

Thank you all who helped!

Yup all the power ratings add up, but the lower resistance resistor will carry slightly more power than the higher res ones - not an issue though. A single half watt 68k can handle it but it would run hot. It will run fine as you have it.

Glad to have helped!