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  #21  
Old 09-03-2008, 06:59 PM
VW cat VW cat is offline
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Went to the "Source" today. They had everything I needed. The smaller female terminals will work. Checked the resistors with that old analog meter I have and they were pretty close. What do you think GWIZ? Phil
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Last edited by VW cat; 09-03-2008 at 07:05 PM.
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  #22  
Old 09-04-2008, 02:28 AM
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GWIZ GWIZ is offline
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Looks fine, but the female terminals go on the 9v circuit.
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  #23  
Old 09-04-2008, 02:37 AM
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With out getting too technical.

Lets look at the IGBT as a relay or electronic switch.
We have the control voltage that comes from the 9 volt battery, It will trigger the IGBT with about 9 volts @ .009 amps.
the light bulb that draws .250 amps should come on when triggered.

===
Static charge.
The IGBT's are sensitive to static.
Before you start.
It would be best to touch a water pipe or something that is grounded.
I know when I wear a particular shirt (I think synthetic), I get a good shock when I get out of my car.

The small pins (8 - 11) are sensitive to the static. Don't touch them any more then you have to.

===

There's two transistors (Q1, Q2) in each block, so we test Q1 then Q2 on the same block.

Q1 test.

Pix 1.
Note, do not connect 9v battery at this time.
Just connect the 9v circuit as pictured (note the polarity of the wires).

Pix 2.
Set your meter on the diode check setting and record the voltage reading on paper.
I want to compare the readings with my IGBT's (0.371 volts).

Pix 3.
Connect the light bulb circuit as pictured (Note wire polarity).
If the bulb lights, Q1 is shorted (bad IGBT).

Pix 4.
Connect the 9v battery.The light should come ON.
and OFF when the battery is unplugged.
(That shows the basic relay switching function).


Now unplug the 9v battery.
Now test Q2 on the same block (next post).

Pix 5.
Is just for reference.
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  #24  
Old 09-04-2008, 02:45 AM
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GWIZ GWIZ is offline
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Static charge.
It would be best to touch a water pipe or something that is grounded.

The small pins (8 - 11) are sensitive to the static. Don't touch them any more then you have to.

===

Q2 test.

Pix 1.
Note, do not connect 9v battery at this time.
Just connect the 9v circuit as pictured (note the polarity of the wires).

Pix 2.
Set your meter on the diode check setting and record the voltage reading on paper.
I want to compare the readings with my IGBT's (0.371 volts).

Pix 3.
Connect the light bulb circuit as pictured (Note wire polarity).
If the bulb lights, Q2 is shorted (bad IGBT).

Pix 4.
Connect the 9v battery.The light should come ON.
and OFF when the battery is unplugged.
(That shows the basic relay switching function).

Unplug the 9v battery.

Pix 5.
Is just for reference.
===

That will have to do for the testing of the IGBT's.
There's still a chance for intermittent problems, breaking down under higher voltage or higher current.
Thermal problems...Blah..blah....blah...
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  #25  
Old 09-04-2008, 07:52 PM
VW cat VW cat is offline
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GWIZ,
Tested both IGBT's. I noted that before removal from the machine, the red and white wires attached to terminals 8,9,10, and 11, were connected with white always on the outside terminal. Also note that both these blocks are trying to 'open' as if the glue on one end is not holding.
Block 1: Q1 test - meter on diode setting- .340
- light did not come on
Q2 test - meter on diode setting- .339
- light did not come on
Block 2: Q1 test -meter on diode setting- .OL
- light did not come on
Q2 test - meter on diode setting- .OL
- light did not come on

Everything look ok in the pictures? Phil
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  #26  
Old 09-05-2008, 02:01 AM
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GWIZ GWIZ is offline
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Something may not be right.

Test the light.
You have two AA batteries totaling 3 volts.
The light bulb should be 2-1/4 volts.
Connect the two wires together and see if the bulb lights.
Look on the base of the bulb, some times they will stamp the voltage on the base.

Also double check the polarity of the wires with your meter.
And double check the polarity on the 9 volt wiring with your meter.

===
Your forth picture is wrong for a Q 2 test. the light is on the wrong screws.
Also look at the pictures and note that the diode test for Q 2 is on screws 1& 2

Look at the reference pictures # 5 for Q1 and Q2.


A note on the diode test,
The OL can mean two things.
The part is open OR you need to swap the red lead with the black.
Look at pictures and note which color lead is on what screw.

The Diode test will read a voltage in one direction and OL in the other, that's when switching the leads around.

Last edited by GWIZ; 09-05-2008 at 03:00 AM.
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  #27  
Old 09-05-2008, 05:56 AM
bunkclimber bunkclimber is offline
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Default IGBT's

Quote:
Originally Posted by VW cat View Post
GWIZ,
Tested both IGBT's.
Everything look ok in the pictures? Phil
VW,when I work on an amplifier thats been fried,my school of thought has always been to replace ALL the pre-driver,bias and driver transistors in a failed amplifer.Your welder is similar,altho the IGBT's can withstand a hell of a lot more abuse..they ARE static sensitive,tho and you should be wearing a wrist strap to avoid static damage to components,and more importantly,the driver circuit board.Your 'sense of perception' of static electricity buildup is around 400V,it only takes about 25V of static to damage a board or transistor semiconductor(depending on conditions).If you don't have a wrist strap,then run a clip lead from the chassis of the welder to a good building ground as best you can.This will HELP but not eliminate the static hazard.The IGBT's you have are expensive,you might dump about $100/ea in small quantities(<25pcs)to get your hands on the qualified proper replacements.If you can replace all of them,jump up a range on the voltage rating of the IGBT,if the stock ones are rated at 400V,try going to a 600V or 800V rated IGBT..much more tolerance for abuse when in circuit.Be sure to use the white or pink silicon thermal grease(available at Radio Shack)between the IGBT and the heatsink.
best of luck with your repair..run the $$ numbers on all of it before you buy any parts..there's probably a reason this unit was sitting in the shop and WASN'T repaired..

Last edited by bunkclimber; 09-05-2008 at 06:01 AM. Reason: technical
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  #28  
Old 09-05-2008, 05:58 AM
VW cat VW cat is offline
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Your right GWIZ, I didn't have the leads in the right place for the Q2 test.
Redoing the test from start, I got these results:
Block 1: Q1 test - meter on diode setting- .346
- light did not come on
Q2 test - meter on diode setting- .OL
- light did come on
Block 2: Q1 test -meter on diode setting- .OL
- light did not come on
Q2 test - meter on diode setting- .OL
- light did not come on

Polarity checked both 9V and 3V battery leads. They are okay. Bulb lights if leads are connected. Switching the meter leads around on the diode tests made no difference. Phil
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  #29  
Old 09-07-2008, 03:24 AM
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GWIZ GWIZ is offline
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Quote:
Originally Posted by bunkclimber View Post
VW,when I work on an amplifier thats been fried,my school of thought has always been to replace ALL the pre-driver,bias and driver transistors in a failed amplifer.Your welder is similar.

<snip>

best of luck with your repair..run the $$ numbers on all of it before you buy any parts..there's probably a reason this unit was sitting in the shop and WASN'T repaired..
What bunkclimeber is saying, also check or replace all the components that feed the signal to the IGBT's.
That would get too involved without a good schematic.

That's the shot gun approach and on your driver board would require replacing about 10 capacitors, 6 to 8 transistors, 11 integrated chips.
Unless you have experience with removing 16 pin IC's that's not going to happen.

bunkclimeber is comparing a stereo amplifier and he's correct. in an amplifier the failure of the power transistor usually feeds back into the other circuits and fries the drivers.

Fortunately your welder appears to use 8 transformers for the IGBT's and more then likely isolate any feed back into the driver board should a IGBT fail saving the driver board. I hope.
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  #30  
Old 09-07-2008, 03:32 AM
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GWIZ GWIZ is offline
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Quote:
Originally Posted by VW cat View Post
Redoing the test from start, I got these results:
Block 1: Q1 test - meter on diode setting- .346
- light did not come on
Q2 test - meter on diode setting- .OL
- light did come on
Block 2: Q1 test -meter on diode setting- .OL
- light did not come on
Q2 test - meter on diode setting- .OL
- light did not come on
Those two are also bad, That's what I suspected from day one.
I was hoping that only the two were bad because two were only removed.

That pretty much proves, if one IGBT fails they all fry. or if one signal from the driver board to one IGBT fails all the IGBT blocks fry.
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