Ok so I’ve worked out the live and neutral - it’s just the relay - have two wires coming from the pcb which I take will go to the relay white and a blue - and then two other ones - one from the max switch and another from the neutral side , Iam thinking white on the max switch is live ? But which way round would the white and blue go on the pcb
The relay coil will run on 12v ( maybe 24v ? ), coming from the PCB when the torch trigger is pressed. These small relays are normally single pole, so will switch either the Live or the Neutral to the transformer ( via the MIN/MAX and 1/2 power range switches. There will not be both Live and Neutral going to the relay.
The small transformer on the PCB will output 12v ( or maybe 24v ) AC. There will be a rectifier - could be just one diode, or a small black plastic bridge rectifier, circular or rectangular, marked with two squiggles for AC and plus & minus symbols. This DC voltage will be controlled by the torch trigger switch. The relay contacts, normally open, will switch the AC mains to the main transformer. As mentioned, this will be either the Live or the Neutral feed. The relay coil will be the other two wires, which may be the white and blue that you are asking about. Since it is just the relay coil - an electromagnet - it does not matter which way round these are connected.
Hi Eddie , thanks for the reply , yes this one is the one without the relay on the board , Having to work backwards with this one as it came in pieces , and the board Is in a bad way as I think they have tried to repair in the past , so if I can get wired up correct way I can then see what’s wrong , pretty sure the way they had the relay was with a neutral and live - will get some pics up - yes I seen that diagram but my schematic reading is very limited at the moment as Iam still learning - I appreciate your help , thankyou
So I might have the live and neutral the wrong way on my colours as this white wire with the blue is coming of the neutral side - then max med low switches have a live feed - is this correct
The diagram that you have marked up in red and blue is correct.
Basically you want mains - live and neutral - to go to the PCB, but only so that it can connect to the primary of the small 12v transformer.
In addition, mains - either live or neutral - has to go to one end of the primary of the main transformer. It goes there via parts of the push-button welding power range switches.
The remaining leg of the mains ( which will be either live or neutral depending on which was already used in the above connection ) will effectively go to the other end of the primary of the main transformer, but via the normally-open contacts of the relay, and also another part of the push-button range switch.
Note:
- those push-buttons often fail, they can sometimes be "fixed" by spraying with switch cleaner whilst repeatedly pressing buttons
- never push the buttons whilst actually welding
- the switches connect to tapping wires from the transformer. The switch selections that connect to the most distant "ends" of the primary ( i.e. the most number of winding turns ) will provide the lowest welding power range.
Hiya bud - thanks again - well I have now got the board in but nothing happening unless I hold the contact down on the relay - I have power going in the transformer and have about 16v coming out - now if I follow that down to that rectifier - then I have about 12v at the rectifier ac then nothing dc - so I take it that has pooped its self - yes switches were sticky so cleaned them up with switch cleaner .
Shaun, it's good that the small transformer is OK; the primaries on them burn out very often. If the secondary is 16v AC, then that is what you should also see at the input to the circular bridge rectifier, on the two pins marked with ~ . You may have to unsolder the rectifier, so that it is out-of-circuit, to confirm what is going on. Usually that small transformer and the rectifier only provide 12v for the relay, controlled via the torch trigger. Power for the wirefeed motor comes from the main welding transformer, via the speed control circuit - which is also on the PCB.
A new rectifier: https://www.ebay.co.uk/itm/W10-Low-Profile-Bridge-Rectifier-Diodes-1-5A-1000V/200738010010
Update - put the rectifier in and now we have the relay clicking and trying to work the motor although it’s hit and miss unless you hold the contacts down on the relay - so will get a new relay and see how it goes - thankyou for your help so far