26 December 1997

ITS VERSATILE AND SOLID, BUT YOU NEED TO KNOW YOUR STUFF

Flag-waving time, as

Andrew Pearce reports on a

high quality British-built

275A MIG set. At £1285

retail, is it a good farm

workshop buy?

IF you want a big single phase MIG, theres a limit on how big it can be. Only so much current can be drawn from one mains phase, and after the sets transformer has done its work, only so much welding current will be on tap.

The most common switchover point in makers ranges is around 250A, though a few – British firm Butters among them – go a little higher. Its equipment sits alongside the likes of Murex in quality, with the Merlyn range spanning 200A-350A. At £1285 less torch, the 275A unit tested here is not cheap, though the spec is good – maximum current delivery is 15A-20A more than most, its duty cycle (see later) is high and build quality looks excellent. So is this particular Butters worth its salt? To find out, weve used one on general workshop duties for more than a year.

Facts and figures

Weighing in at a substantial 90kg, the Merlyn 275 is one solid piece of kit. Outer panelling is 1.6mm steel sheet, fastened by machine screws rather than cheap ncheerful self-tappers. Two over-centre latches hold a drive cover which lifts completely away for good access (Fig 3). Inside, a chunky German-made Aimer wire feed unit with lift-release pressure control accepts rollers for 0.6-1.2mm wire; an unusually wide range (Fig 4). Both 5kg and 15kg spools can be used, though theres no spacer supplied to accommodate the smaller ones.

Nearside panelling unscrews to reveal the electrical works (Fig 2). Transformer windings are copper for a potentially long service life and good duty cycle. The rectifier pack has very generous heat sink plates and two fans draw cooling air from rear vents. Wiring is neatly loomed, and – a confidence-booster, this – most of the main components carry a signed inspection tag. Its a unit that has definitely been built, rather than thrown together.

A useful 24 voltage settings (more than most competitors) come from coarse and fine selectors on the sloping front panel (Fig 6) . Also up here is a group of knobs dealing with wire feed speed, burn-back time, spot weld duration and interval. Likewise theres a socket for controlling a spool-on gun, which would be a must if you work a lot with aluminium. But at £1250, youll need to.

Duty cycle (35%) is quoted only at maximum current. So in a 10min period, the set will work flat out for 3.5min before switching itself off to cool. Even compared to other quality tackle thats good, representing a lot of non-stop work.

In line with most single-phase sets the Merlyn 275 has no current or voltage readouts. And it has no facility to deliver unenergised wire (useful for checking feed or when changing spools), but it does come with a resettable overload switch under the wire drive cover.

Practicalities

As the set can draw heavy current from the mains, it needs a proper switched supply with 32A connectors (Fig 7). Mains cable length is not over-generous at 3.0m, implying the need for more when working around machinery; using the set with a 10m extension produces no noticeable performance drop.

Turn on and the set runs with impressive hush. On pulling the torch trigger, the sets current-delivering contactor operates with an encouraging thud. Changing wire spools is straightforward as theres enough space in the compartment to manhandle a fresh one into place, and the wire drives pinch roller flicks open without fiddle.

Working with wire diameters from 0.8mm to 1.2mm and 20% CO2 shield gas on mild steel, its easy to find good dip transfer welding conditions and then move about in them. Two things let this happen: Plenty of voltage adjustment steps and progressive wire feed control. Spatter-free transfer is simple to achieve, and the set lets your ears know when youre moving into unwanted globular transfer. Given a clean contact tip and a decent spool of wire, the arc is stable and wire feed rock-steady. Pinch roller pressure is a doddle to set, and feed is positive enough to deal with gentle wire kinking.

Stable spray transfer is readily on tap with 0.8mm wire, just achievable with 1.0mm wire and not available with 1.2mm.

One timer allows stitch or spot weld duration to be set, a second varies the interval between stitches. Duration control is usefully wide in both cases. Although the facility probably wont see much use in general repair work, it comes in handy when fabricating. Similarly, the sets variable burn-back control is worthwhile at high feed speeds to limit residual wire stick-out, and at other times to keep an envelope of shield gas around a weld finish.

Troubles and summing-up

On delivery, zero burnback couldnt be achieved. This was sorted out by taking off the main cover and gently twiddling the circuit boards controlling potentiometer. Otherwise, the Merlyn has not put a foot wrong in 12 months of use by several operators. If it does, theres a warranty to fall back on which covers the rectifier pack for five years and other major parts for three years.

Criticisms are few. The wire feed speed control could be less sensitive, as a small change can have a very significant effect at the arc. Moving the on/off switch so its illumination is easier to see would help, and the mains supply lead could be longer. Finally, a decent torch should be included in the price; as it is, youll need to find around £80 for a Binzel-pattern item.

So, is the Merlyn 275 a good farm workshop buy? Definitely, thanks to its solid build, ability to deliver high current from a single-phase supply and to handle a wide range of wire sizes.

Theres only one caution – simply because the Merlyn 275 has such a wide range of possibilities, the operator needs some small idea of whats going on to get the best from it.

WIZARD STATISTICS

Model: Butters Merlyn 275.

Power supply: 240V, 30A mimimum

Voltage settings: 24.

Voltage range: 17V-28V.

Duty cycle: 35% at 275A.

Wire diameters: 0.6mm, 0.8mm, 1.0mm, 1.2mm.

Spool sizes: 5kg, 15kg.

Weight: 90kg.

Warranty: 5 year limited.

Retail price (less torch): £1285.

Supplier: Butters Ltd (01299-250546).

1: Butters Merlyn 275: high single-phase output, and its a British machine.

3: Two over-centre catches hold the spool compartment cover.

6: Front panel offers 24 welding voltages on two selectors (bottom right), plus rotary controls for wire speed, spot/stitch duration and interval, and burnback. Socket (centre) allows remote gun operation. Torch (centre left) is not supplied with set.

2: Copper-wound main transformer (bottom) gives potentially long life and good duty cycle. Twin fans (centre right) run quietly. Wiring is generally neat and tidy. Its a unit thats definitely been built, not thrown together.

5: Gas cylinder restraint is by conventional chain and hook.

4: Pinch roller pressure/release comes from one toggle. Wire feed is rock-steady across the whole speed range.

7: No 13A plugs, please – sets potential current draw requires 32A mains connectors.