Is it just me, or are a lot of folk on here of late turning into right old pussies who are starting to shun blokely reasons for buying new kit, or spending inordinate amounts of time making something which would be much easier & cheaper to buy? C'mon lads, the worlds going mad if people can't rely on us lot to justify unjustifiable things. Up yer game.
Nah, I openly admit I'm a tight fisted git when it comes to buying something new! When I recently bought my new mig, I had to lay down immediately after placing the order, and had to have therapy for three weeks
your better than me i just cant spend on new when there 2nd hand stuff around apart from when new is needed
Is it a Clarke machine? Check the current Clarke posts (as I'm about to reply to one...) A common Blue Clarke should be 18 volts to 28 volts, OCV. If it isn't a Clarke, then it's still too small a voltage range, IME.
Suffering from an open-circuit diode in the rectifier? It is possible, but not likely in this case. If a diode was open-circuit then the rectifier would be providing just half-wave rectified AC, with a gap for half of every cycle of the 50Hz AC. I am not sure what a digital voltmeter would indicate, but I am guessing it would be around half of the normal RMS voltage. The "low" reading of 18 volts that you see is about the right voltage for the 20 Amp setting of a hobby-grade welder, so I do not think a diode has gone open-circuit. The problem is with the "high" power range of just 22 volts. That is not enough to source 135 Amps of welding current. It is also not enough of an increase to be Step 4 of a 4-step welder that starts at 18 volts. If power setting 1 is 18v, and step 4 is 22v, what voltage are the intermediate two steps? Assuming these voltages are open-circuit, I would suggest testing with a small load consisting of 2 x 12v 60 Watt car headlamp bulbs in series ( drawing about 5 Amps ), then re-check the voltage steps across this load. [ Does your machine have four or only two "effective" diodes in the rectifier, i.e. does the transformer have a normal secondary with two thick wire connections, or are there three wires? The latter would indicate a centre-tapped secondary ( e.g. 20 - 0 - 20v ), which only needs 2 active diodes to get full-wave rectification.] I suspect the fault is not the rectifier, it is on the primary side. The most common issue would be loose connections or burnt contacts on the power range switches.
Eddie can the reverse happen? In paper my welder has 16v(20 amps) to 22v (140 amps). In my case the lower setting is 18,5v and the higher 21,5 or 22v in the last of the four stages
By "the reverse", do you mean that a diode is short-circuit as opposed to open-circuit? Normally the effect of that is too much current draw on the primary side, and mains fuse or breaker trips. To find why your power ranges are not correct: test the DC output voltage at all 4 steps, test with a slight load as suggested above, check the secondary AC voltages before the rectifier, verify that the maximum wire speed is adequate ( around 8 to 10 metres per minute ), post pictures of weld beads at all 4 settings on 1mm to 3mm thick steel.
what did i mean is why does my welder only give 18,5v to 21,5v range in all 4 stages when in paper it should have 16v to 22v.
It's worth cleaning the contacts of the two rocker voltage switches to ensure a good connection without high resistance.
