PDA

View Full Version : Idealarc tig 250 high frequency problem



blueovalz
02-22-2007, 10:54 PM
I've recently acquired an old Idealarc tig 250. It worked in all modes (very well), but yesterday, I noticed the high frequency portion is not working at all. The welder appears to operate very well in all other modes (DC, Stick in AC and DC, and normal tig), but lacks any high frequency start or run. In fact, it's nearly impossible to weld in the AC tig mode as a result. I've checked all switches in their correct setting (I even checked to make sure the spark switch was working correctly with an ohm meter), I've checked the spark gap (which is fine). Lincoln tech did not provide any useful ideas or tips, so I'm asking:

Where would I start to trouble-shoot this equipment so that I get the high frequency part to work correctly (I've got some limited electrical and electronic skills and knowledge)?:cry:

gnm109
02-26-2007, 12:59 PM
I've recently acquired an old Idealarc tig 250. It worked in all modes (very well), but yesterday, I noticed the high frequency portion is not working at all. The welder appears to operate very well in all other modes (DC, Stick in AC and DC, and normal tig), but lacks any high frequency start or run. In fact, it's nearly impossible to weld in the AC tig mode as a result. I've checked all switches in their correct setting (I even checked to make sure the spark switch was working correctly with an ohm meter), I've checked the spark gap (which is fine). Lincoln tech did not provide any useful ideas or tips, so I'm asking:

Where would I start to trouble-shoot this equipment so that I get the high frequency part to work correctly (I've got some limited electrical and electronic skills and knowledge)?:cry:

Hi,

The link below is to the manual for one of the several versions of that machine. I have the same one, the 250/250 TIG/Stick. Mine is dated 1984.

The electrical schematic is on pages 27 and 28. If you don't already have the manual, I guess you could download the whole thing and print it.


http://www.mylincolnelectric.com/Catalog/operatorsmanualdatasheet.asp?p=32560

In any case, page 27 shows the schematic for the high frequency section of the machine. It's toward the top of the page since the page is printed sideways.

When you look closely at the diagram, you will see that the spark gap points are in the center of a circuit which contains the following:

1. High frequency transformer in series with the working electrode. The other electrode is called "work". This would be the ground as I read it.

2. One leg contains a "high frequency capacitor".

3. On the other side of the spark gap points is a pair of RF chokes. leading to the high voltage transformer.

4. High voltage transformer.

Power to the above circuit is controlled by the spark switch which you have already checked out as good. Coming off of that spark switch is a small unit which has no identification on it. Could be a resistor, diode, or?

To answer your question, I would open the case and identify the two transformers (1 and 4 above) and the high frequency capacitor (3) and the two chokes (2) as well as the "mystery unit" shown on the schematic.

It appears to me that the machine will operate wthout high frequency if any part of that circuit is open. I would unplug or un-wire the machine from your power source and then isolate the transformers. You could then check them for opens or any burning and also the capacitor and RF's at that point.

For your safety, I would watch for charged capacitors in the circuit. Perhaps you could wear rubber gloves and/or discharge anything nearby?

It seems to me that your problem simply has to be in that circuit and it looks like a fairly easy fix, assuming you find a bad component.

I sure like my old machine. It's a good TIG and a great stick welder.

Good luck. Hope this helps. :)

duniqueone
04-17-2007, 10:05 PM
i have a square wave tig 175 that is doing th exact same thing.
i have looked at the manual and inside the machine but i can find the problem.
called one place local that wants $95 to look at it.
amptroler looks like its working gas comes on and power can be controled but wont tig till i scratch start.

thanks

prop-doctor
04-18-2007, 09:58 AM
a fews years ago mine (idealarc 250) let me down also
took to the repair shop and they found the hi freq board bad
cost $250 with labor
i did see a burnt resistor on the board but what made it go bad ???
so we just replaced the whole board
GOOD LUCK

duniqueone
04-18-2007, 10:17 AM
i was looking at that board but its buried in there and i did not want to pull it apart.
ill take a second look

also are there any web sites where i could order this part if it looks like its blown?

thanks for the help

prop-doctor
04-18-2007, 10:25 AM
the board is easy to get to if you remove front panel
if i remember its behind the louvered panel
make sure to UNPLUG MACHINE

duniqueone
04-18-2007, 11:42 AM
will do
thanks

GONWHLN
11-16-2007, 03:38 PM
I had the same problem with my mid 80`s 250/250 tig found that the hf coil that transfers HF to the weld leads (big aluminum coil with a small copper wire coil in the center) small coil windings burnt out.Couldn`t find a replacement part so I modified a blue machine part (wired it in following wiring diagram compared from both machines).works perfectly now. PS. blue machine part is smaller in size and still available from factory,as of 2 years ago anyway.