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Old 07-20-2010, 12:22 AM
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Hobweld Hobweld is offline
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Default Capacitor Mod on Astro pocket turbo 130

Ok, all you electrical gurus. I am in need of some help deciphering the schematic and I am stuck on a question.

I will be adding a 100000 uF Capacitor 50 V to this welder.
I have pretty much figured out the connections for it and the bleed resistor.

I am having a problem with the additional bridge rectifier connections. The pcb and drive motor in this unit get voltage from the gun when the trigger
is pulled.
Now how to wire in the second rectifier to isolate the pcb and drive motor and not fry them when I pull the trigger. The person who sent me this diagram added a euro torch to his and it has a two wire lead from the gun where mine is a single lead. He also added a 120 gas solenoid, since the old torch had a mechanical valve in the handle.
I don't want to replace the torch if I don't need to. Any Ideas?

Ken
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Old 07-20-2010, 12:26 AM
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Here are a few pictures of what his looks like all done up.
Ken
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Old 07-20-2010, 01:50 AM
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Quote:
Originally Posted by Hobweld View Post
Ok, all you electrical gurus. I am in need of some help deciphering the schematic and I am stuck on a question.

I will be adding a 100000 uF Capacitor 50 V to this welder.
I have pretty much figured out the connections for it and the bleed resistor.
Ok.

Quote:
I am having a problem with the additional bridge rectifier connections. The pcb and drive motor in this unit get voltage from the gun when the trigger
is pulled.
The trigger is just a push button. the welding voltage also supply's the power to the board.

Quote:
Now how to wire in the second rectifier to isolate the pcb and drive motor and not fry them when I pull the trigger.
The original was not isolated, what makes you think it needs to be isolated?
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Old 07-20-2010, 02:17 AM
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By adding the capacitor,the drive motor runs extremely fast, and the speed adjustment has no effect. The cap affects the speed controller. Adding in the second rectifier acts as a isolator and problem was solved.

They also added another 100uf 35V capacitor to the wire feed motor to help smooth the wire feed a bit.

Ken
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Old 07-20-2010, 02:46 AM
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It's getting late so I cant go into details.

You could probably add a relay.
have your gun trigger the coil and the normally open contacts of the relay connected to the two trigger wires on the new drawing. may have to add a resistor to a 24 volt relay.
adding the larger cap probably brought the voltage up around 35 volts.

As for the new motor capacitor, looks like they have its polarity marked wrong and it should be more like 50 volts or more
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Old 07-20-2010, 08:53 AM
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Quote:
Originally Posted by GWIZ View Post
It's getting late so I cant go into details.

You could probably add a relay.
have your gun trigger the coil and the normally open contacts of the relay connected to the two trigger wires on the new drawing.
That is the problem. I'm trying to get by without buying a new gun. My gun only has one wire.

"Actually the motor negative is going to the negative on the bridge, but the way the original diagram is drawn, appears to connect to the positive, maybe I should have redrawn it to show it passing past the positive connection. I didn't draw the original diagram, it was a download from manufacturers website" His words.

Ken
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Old 07-20-2010, 10:27 AM
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I'm tied up this morning to make you a drawing, maybe around 1pm.
you should be able to add a relay and use the gun you have.
you would remove the two wires A3 and A1 (old drawing) ,and use them to power the relay.

Use the two relay contacts to trigger the two wires (gun) as on the new drawing.
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Old 07-20-2010, 10:53 AM
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Default Here Ya Go

Here ya go, Hobby! It's very straightforward. You're just duplicating the rectifier and filter of the first gun. Make sure to heat sink and cool the rectifier module with a fan. I've often thought I'd like to do the same to my MM180 so I could have my spoolgun always attached but I'm too lazy to plumb the gas fittings!

If I ever do it, I will bolt a metal box to the top of the welder and run the DC, Gas and control voltage to it. That way I won't mar the beautiful miller front panel and I could always restore the welder to original condition.

DrBob
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Old 07-20-2010, 11:04 AM
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Ken,
I don't understand the Original post.

What are you trying to accomplish ? do you want to smooth
out the welding voltage somewhat ? are you trying to make
a "stiffer" supply so that the short arc current goes up ?

Or/and fixing this "single wire gun switch" problem ?
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Old 07-20-2010, 12:43 PM
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Quote:
Originally Posted by DrBob View Post
Here ya go, Hobby! It's very straightforward. You're just duplicating the rectifier and filter of the first gun. Make sure to heat sink and cool the rectifier module with a fan. I've often thought I'd like to do the same to my MM180 so I could have my spoolgun always attached but I'm too lazy to plumb the gas fittings!

If I ever do it, I will bolt a metal box to the top of the welder and run the DC, Gas and control voltage to it. That way I won't mar the beautiful miller front panel and I could always restore the welder to original condition.

DrBob
DrBob
I will be adding the large cap and bleed resistor at the original rectifier,sooo basically for the small bridge rectifier I am adding I could just pull AC of of the input to the main rectifier, and then attach as you said? Correct?
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