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Up Topic Welding Industry / General Welding Discussion / Linde 250 HF arc starting
- - By yalisan (*) Date 06-09-2003 00:27
I have an old Linde 250 HF welder that seems to work fine except that when trying to start the arc during tig welding I have to touch the base metal to start. I know that the machine is setup properly because I have the manual for it, I have adjusted the spark gap to proper specs, any advice on what to check will be appreciated.

Thanks
Parent - - By RonG (****) Date 06-09-2003 16:51
Do you have a stinger and cables hooked up also?
SMAW leads tend to soak up the Hi Freq.
Parent - - By yalisan (*) Date 06-09-2003 22:43
Actually I did have the stinger cable hooked but I just took it off and haven't checked since. One thing that I did notice is that the hf start seemed to work better when the tungsten was hot??????, am I tripping or is this possible. Thanks for your input

O. Sanchez
Parent - By billvanderhoof (****) Date 06-10-2003 04:45
You aren't tripping. Heat causes electrons to "evaporate" into the space around the negative electrode (an important fact in vacuum tubes). If that electron cloud is moved into contact with a conductor an arc is more easily started.
Bill
Parent - - By swank (*) Date 06-10-2003 06:49
i've got the same welder, made in 83, and the same problem. not so bad with a fresh tungsten though. i have noticed a very small spark sometimes when i touch the base metal. every time i get one of those, i have no problems starting the arc. ?????? still trying to figure it out.
Parent - - By yalisan (*) Date 06-10-2003 21:21
Now that Swank mentions it I believe my does similar things to his. I am a rookie at tigging so I'm not very familiar with these things and I just recently acquired this machine and besides that problem, it all seems to work fine. Thanks to all for your input,

O. Sanchez
Parent - - By swank (*) Date 09-23-2003 18:17
figure it out yet?
Parent - - By yalisan (*) Date 09-24-2003 00:38
Hey what's up. Finally figured out shorlty after all the help. Make sure the stinger isn't hooked up and that the spark gap is correct. I cleaned the contactors (spark gap things) and adjusted the gap and my problem was gone. If you need more help I have the user manual for this thing.
Oh also I think pure tungsten helped.

O. Sanchez
Parent - - By swank (*) Date 09-24-2003 22:57
yeah, the service guy just told me to double the spark gap. haven't tried yet. will let you know how it turns out.
Parent - By yalisan (*) Date 09-25-2003 23:45
Yes please let me know if that helps, mine is working fine now but I'm always willing to experiment.
Parent - - By brande (***) Date 09-28-2003 04:36
Be careful increasing the spark gap. A .003-.005 increase or so shouldn't cause a problem. Increasing much over that can damage your hi-freq capacitors by over voltage. (which might be the problem in the first place).

Other items to check....
Correct gas flow 10-25 cfh. Too much gas can hurt starting.

Quality torch parts (collets, collet bodies, etc) from a reputable mfg such as Weldcraft, CK, Tec, and others. I've found the generic stuff is not as good. As long as we are on torch parts, they do not last forever and become worn easily. (air cooled torches are more susceptable, but it happens to water cooled as well). Replace with some regularity.

Oxides from welding can, and do, adhere to the tungsten electrode. Especially prevalent on stainless and mild steel, it can happen on all materials. I've found a quick, but light swipe of the tungsten(while the weld current is off!!) on the work or other clean place can help starting performance.

Hope this helps
Good Luck
brad

Parent - - By swank (*) Date 10-06-2003 07:08
how quickly will the damage be done?
Parent - - By brande (***) Date 10-11-2003 07:06
The damage may be quick, or possibly not. Depends on the amount of gap over standard, quailty of the hi-freq caps, frequency of use and so on.

>Look at your hi freq caps. If you see wet around it's mounting or terminals-it is shot.


>Non-weeping caps can be bad as well. Testing a hi freq cap takes something more than a Fluke volt/ohmeter, due to it's rating or capacity. The standard volt/ohmeter does not have the range needed. Usually a dedicated capacitor tester is needed to get an accurate evaluation.


Often, it is really not as hard as all that. You can apply the process of elimination with decent, reliable results.

Check to see....

>Your connections are good. Throughout the system, including the coupling coil.
>You have good 120vac input to hi freq transformer. Remember to test the input wires and not when the transformer is connected. The 2500-4500 volts available from the hi freq transformer will waste a good meter instantly.
>Your tig torch is in good condition. Substitute another tig torch to be sure.


>New collet/collet body and only use ground, not just cleaned tungsten.


Spark gaps set to factory specs. Clean spark tips. Most are tungsten carbide and cannot be filed, but a sanding or other abrasive cleaning so they shine is good. You will find that the hi voltage of the hi freq system can often ionize shop dirt and deposit same on the face surfaces of the hi freq points. Often this ionized dust is not very conductive.

>If these tests are completed, and still you have a low spark, replace the hi freq caps. You will probably find the cure there. Be sure, though. Hi frq caps can cost as much as $70.00 each, and remember, there are usually two.


Sorry for the delay-I don't check messages as often as I should.

In the future, contact me directly for faster response!!

Let us know how you make out!!!

Good Luck
brande
Parent - By yalisan (*) Date 10-15-2003 21:15
Thank's for all the good info.

O. Sanchez
Up Topic Welding Industry / General Welding Discussion / Linde 250 HF arc starting

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