Miller Syncrowave 250DX welder Amperage problem

This machine is a 2004 model used for tig with a water cooled torch and foot pedal remote control. The problem started when the remote
cable was damaged causing the machine to give an error code 12. The foot pedal cable was repaired and the machine now starts up normally. Now I can strike an arc but cannot get the machine to go over 56 amps. The foot pedal appears to control the amperage but maxes out at 56, even with the front panel amperage control set to max. The amperage indicator reads up to 310 amps when idling but while welding, never goes over 56. To try and isolate the problem, I switched to panel control of amperage and in this condition full amperage is delivered. Since we have other machines in the shop, I swapped in another pedal resulting in the same problem. (And the first pedal works fine on the other machine.) My guess is only two things remain, either the wiring from the plug to the mother board or the motherboard itself. I am hoping someone can suggest other tests or possibilities Thanks! Eug
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Two suggestions:
1. Re-post this on the sci.engr.joining.welding NG.
2. If you don't have the manuals - especially the wiring diagrams - for this unit, go to the Miller website and download them..
Of course, you COULD just place a call to your Miller Dealer/Distributor and see what they have to say...
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I think that this is a simple problem.
Get a manual for the RFCS-14 pedal.
Find out which three contacts are for the potentiometer common, ground, and wiper. Measure resistance between two ends, and then between one and wiper as you engage the pedal.
The latter should change from zero to the first value.
if it does not, you probably found your problem.
i

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Ignoramus14593 wrote:

He swapped in a known good pedal and the problem didn't go away, so it's not the pedal or pedal cable. Sounds like something is blown in the box itself.

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Have you tried "Reset to Factory Settings" yet? From: http://www.millerwelds.com/om/o363w_mil.pdf
"To reset all welding power source functions to original factory settings, turn power off. Push and hold the Process, Amperage, Output, and Start controls and turn On power. Hold switch pads for approximately 7 seconds (or until software version number _ _ _ _ _ _-_clears meters)."
--Winston
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Eug wrote:

The main box sends a current through the pot in the foot control, and senses the voltage on the slider. There is most likely a resistor on a board in the main box in series with the pot in the foot control, and the shorted cable has burned up that resistor. Open the machine and examine the boards for a burned part. You may need to trace the wires from the foot control plug back to find the burned part. (It is possible that the component's value has changed, but the part is not totally charred to a crisp.) If you can find a burned component, check one of the other machines to be able to read the part value, and replace. With just a little luck, you should be able to fix this for under $1.
Jon
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This machine is a 2004 model used for tig with a water cooled torch and foot pedal remote control. The problem started when the remote cable was damaged causing the machine to give an error code 12. The foot pedal cable was repaired and the machine now starts up normally. Now I can strike an arc but cannot get the machine to go over 56 amps. The foot pedal appears to control the amperage but maxes out at 56, even with the front panel amperage control set to max. The amperage indicator reads up to 310 amps when idling but while welding, never goes over 56. To try and isolate the problem, I switched to panel control of amperage and in this condition full amperage is delivered. Since we have other machines in the shop, I swapped in another pedal resulting in the same problem. (And the first pedal works fine on the other machine.) My guess is only two things remain, either the wiring from the plug to the mother board or the motherboard itself. I am hoping someone can suggest other tests or possibilities Thanks! Eug
Hi Eug Since you have more than one Sinchrowave and would like to fix the welder without involving a welder repair shop, you may consider swapping out the PC1 board, It controls both the on-off and the amperage . I also assume you have attempted to control the amperage with the front panel setting. The amperage control for my Synchrowave 250 is a 1000 ohm pot.
Jerry
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I whish to thank everyone who answered, I was going to post this to a welding forum but their registration process has malfunctioned. In the interest of brevity, I left out many of the steps I have taken in troubleshooting this problem. Here are short answers to issues raised. I have all manuals and schematics. We have six machines in the shop from old dial arc 250s to 3 generations of Syncrowave 250s. Cant run to dealer every time someone rolls over a cable. The foot pedal was eliminated. I have reset to factory defaults.
Since my first posting, I have checked the wiring from the front panel plug to the circuit board and found no problems. Next Ill remove pc1 board and check for damage as suggested by Jon Elson. Again, I want to thank everyone who replied Eug
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Eug wrote:

There is no registration process...

is a usenet group just like this one and very helpful, and spam/OT free

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Eug wrote:

(...) Hi Eug,
I would like to know if there is an issue with the 10 VDC *going to* the 'Remote 14 Receptacle' or *coming back into* the 'Remote 14 Receptacle'. Please see diagram 3-8 the top of page 14.
http://www.millerwelds.com/om/o363w_mil.pdf
Can you temporarily clip a DC voltmeter on the circuit board: 1) First, between return (Same as Pin D) and 'Output to remote control' (Same as Pin C) 2) Second, between return (Same as Pin D) and '0 to +10 volts dc input command signal from remote control.' (Same as Pin E)
In 'Remote' mode you should see a constant 10 V on the first meter position and on the second meter position you should see a voltage that varies from nearly 0 V to 10 V as you press on the remote amperage control pedal.
It sounds as if you get not much more than 1.81 V *to* the pedal if the problem is on the 'left' side of the pedal (signal going into the pedal) *as Jon Elson said.*
Alternatively you should look on the 'right' side of the pedal (signal processed by the circuit board) if you see that the pedal gets its 10 V reference and outputs 0-10 V as outlined above.
Divide By Two, and Conquer! (Phil Gold, 1982)
--Winston
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wrote:

Did you make sure the replacement cable was the right one, and wired correctly? You've swapped the pedals, but not the cables - try swapping the new cable to the other machine and see if the problem follows.
If you have then I have to agree with others, it might have fried something on the mainboard inside the welder.
A short on a pedal shouldn't be able to blow up expensive bits inside, but while chasing the dollar to the bottom companies can't afford to build machines like that. If you build a 100% bomb proof machine that keeps working no matter what - but it costs twice as much as the competition, it's a hard sell to get people to pay a lot more. A few will, but in mass production you need many...
--<< Bruce >>--
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