SIP Autoplus 120 - repair options - weak spark?

[Nicolasticity]

I have an old (1970's) Autoplus 120 machine which about 3 years ago stopped working.

Fault is that the spark from the wire to the metal is like the brown spark from a tired lawnmower ignition system. Feed is still good (better than a replacement Migmate 105 Turbo) but no heat!

Kept the machine as I thought it could be repaired and you guys have fixed my Spotmatic so;

Is it repairable - should I bother?

What should I check?

 

[R Kraft]

May have burnt out the diodes in it, or have a bad connection.
A bad switch may also be a possible thing to check.
Robert

 

[Nicolasticity]

Machine looks fair inside - nothing burnt out. Dated 23 March 1985 so I didnt get it in the 70's.


Pics attached,

Any advice on checking the diode pack - the silverplates in the picture on right - I know diodes pass current in one polarity only so guess I can check with an avo with cables removed.

Switch wire feed seem OK its just the juice in the spark that seems to be at fault.

thanks for help.

 

[dai]

prod the small wires coming of the diodes with a screwdriver to see if they are still attached

mine had come loose but looked ok

 

[R Kraft]

You might try testing the DC voltage across the capacitor, the yellow can thing bottom center.
Just press the torch button and see if you get around 30v DC.
Robert

 

[Nicolasticity]

Many thanks- I have got to round to working on the machine. Rectifier first pic has about 220 ohms one way and nothing when polarity is reversed, same is true for both banks.?

Capacitor pic 2 measures open circuit with a digital multimeter but does that mean its faulty?

What to we think?

 

[shenion]

That looks ok.

Check voltages next. Also measure resistance between the two wires going to the transformer.

Beyond that, will need to measure voltages.

 

[GeorgeB]

Capacitor pic 2 measures open circuit with a digital multimeter but does that mean its faulty?

What values does the capacitor have printed on the side, like uF and volts?

If it's a smoothing capacitor for the main welding output, SIP don't even use a capacitor in most of their welders these days. It's a luxury most manufacturers no longer afford. So if it were me, I'd take it out of the circuit for testing purposes.

What you should have, and be able to measure with your meter, is 230VAC going into the main (largest) transformer (primary) and about 18-22 volts AC (very approx) coming out the other side (secondary), depending on the setting of any power control knob This AC output then goes into the rectifier (diodes) where it's converted to DC. I suggest you check all of that.

If 230VAC is not reaching the transformer in the first place, perhaps the main relay is faulty.

 

[shenion]

Expect 36-50V AC on the two transformer leads going to the rectifiers.

 

[Nicolasticity]

What values does the capacitor have printed on the side, like uF and volts?

If it's a smoothing capacitor for the main welding output, SIP don't even use a capacitor in most of their welders these days. It's a luxury most manufacturers no longer afford. So if it were me, I'd take it out of the circuit for testing purposes.

What you should have, and be able to measure with your meter, is 230VAC going into the main (largest) transformer (primary) and about 18-22 volts AC (very approx) coming out the other side (secondary), depending on the setting of any power control knob This AC output then goes into the rectifier (diodes) where it's converted to DC. I suggest you check all of that.

If 230VAC is not reaching the transformer in the first place, perhaps the main relay is faulty.

It says;

33000 uF, 63 Vcc, -40 + 85' C GPF, eff 14 Aa 100hZ 85 'C, then I guess a part number 932 333 063, make s Micro.

 

[Nicolasticity]

Many thanks - I get 32V c across the capacitor, and 170V ac to 210V ac from the PCB board to the transformers. So the machine should work?

Still getting a weak spark to the earth cable

 

[shenion]

What voltage do you get between the two red leads going to the rectifier?

 

[Nicolasticity]

What voltage do you get between the two red leads going to the rectifier?

11.6 V AC on in to 56 V AC at max on the dial. Should the answer be 0?

 

[shenion]

56V seems about right. What is the 11.6v reading?

Edit: Still sounds like a loose connection somewhere. Supposedly where the torch connects to the machine is one common problem.

 

[R Kraft]

It seems to be, that a load test of some sort is needed.
Robert

 

[Nicolasticity]

1.6V ac reading is with the dial (current on min)

What is a load test - can I do it?

 

[shenion]

11.6 is is way to low.

Does it work on the max setting?

 

[Nicolasticity]

No at max spark is weak and orange

 

[R Kraft]

A load test is when you hook something that requires a decent amount of power to the output of a power supply.
A large light or a heater element, just something to pull the voltage down and draw some current while you check the voltages.

 

[shenion]

I have used an old 120V heater as a test load. Then measure the voltage drops.