Help needed

[rotivator]

I have a Powercraft No gas turbofan cooled welder 25-130 amp. I have no wire feed. The machine stopped in the middle of welding. I can just about read a meter so I am having difficulties. I can hear the relay click when I press the trigger. I have voltage on the diode. In desperation, I have changed the relay, the diode, and the thyristor. The fuses are ok and I disconnected the motor and it tests ok. I can't see any breaks in the board. Can anyone suggest what I can do to get this thing working?

 

[eddie49]

Usually the relay on the PCB is powered by a low voltage that is the rectified output of the small transformer on that board, routed to the relay coil via the torch trigger switch. The contacts on the relay feed AC mains to the main welding transformer. The rectified welding power is "tapped-off" to also run the wirefeed motor, via the speed controller components on the board.

In your case, the relay clicks, so that part of the circuit works. Relay contacts can burn, but the new relay should have precluded that. Are you getting the main DC welding voltage output? You should be able to strike an arc with the tip of the MIG wire ( even if it will not feed ). The tip voltage ( negative for a "no gas" welder ) should be about 15 to 30 volts with respect to the workpiece clamp and return lead. This will vary depending on the setting of the power switch(es). Sometimes these switches break or burn internally, so it is worth operating them on & off a few times, and also testing for the arc and the wirefeed fault at all settings of the switches.

 

[Hutcho]

Can you post a pic of the board for us to see

 

[rotivator]

I have not been able to look at the welder due to being in hospital. Would like to get it working again but just don't know what to do next. Is it possible to get the panel repaired?

 

[Hutcho]

More than likely that big relay that’s at fault jqx one

 

[eddie49]

As Hutcho said, the JQX-29 relays are known to be weak and they often fail - but replacements are hard to find.
This relay switches the AC mains Live feed through to the primary of the main welding transformer. You could determine whether yours is actually faulty by bypassing it:

Connect two short pieces of mains-capable insulated wire to the right-most two push-on spade tags on the printed circuit board ( CN3 and CN4 in your second photo ). You could use piggy-back spade tag connectors, with the existing wires still in place, or solder the two wires onto the tracks underneath. In this case, in your first photo, these would be the left-most upper two solder pads.
Join the other ends of these two wires to a mains-rated On/Off switch ( e.g. a 1-gang 1-way rocker lightswitch ).
** This switch and the wires will be at 230v mains potential !!
Plug in and power up the welder. Operate the extra switch. The main welding transformer should power up.
Then press the MIG torch trigger switch. The smaller relay should click, the wirefeed should start, and you should be able to weld. If this bypass test is successful, it means the JQX relay is defective and needs to be replaced.

 

[a111r]

You could also stick a voltmeter over the DC side of the relay and check for 12 or 24 vdc.
If present, measure the resistance of the coil (should be something like 200 Ohms) to see if it's burned out.
If the coil is OK but no DC voltage is present, trace backward, via the regulating diode, to the potted transformer, which are another weak link on the small boards.

 

[rotivator]

Where can I get a JQX-29F-A relay, that will just replace the one on the board?

 

[eddie49]

This Polish website offers two alternative replacements for the hard-to-find JQX-29F-A relay:
zamiennik przekaźnika JQX-29
The "Finder" relay for £11 requires small modifications, the cheaper one at £5.50 comes on an adapter board and solders right in.

As suggested in post #6, have you confirmed that the JQX relay is defective?

 

[rotivator]

Do I have to take it off the board to test it?

 

[Hutcho]

Can you here it click or even feel it click - follow what eddie has said to test it -

 

[eddie49]

The test procedure in post #6 will allow you to decide if the welder itself works, by replacing the relay with a manual switch. If the welder then works, you can be fairly sure that the relay is faulty.
To confirm this, you can take the relay off the board ( use a solder sucker or wick, or heat the joints alternately whilst levering the relay off ), and then test the relay itself. Put an Ohmmeter across the flat blade pins that are the two contacts, and apply 12 volts DC from a battery across the two round pins that connect to the operating coil. You should hear and feel the relay armature move inside, and the Ohmmeter should indicate that the contacts have closed by reading about zero Ohms.

 

[rotivator]

JQX is U/S. Any suggestions were to order? Have clicked on the polish site but can't see any way of ordering

 

[eddie49]

The website says they take orders by phone, post, or email. I will send them an email asking if they ship to UK, and if so, at what cost and how to pay. ( I speak Polish.)

 

[rotivator]

Thanks

 

[eddie49]

The Polish website

zamiennik przekaŸnika JQX-29

replied that they will ship to UK, at a cost of 35 Zloty ( £6.54 ), and they accept payment via PayPal. The relay with the daughter-board adapter is £5.61.

 

[rotivator]

Thanks for that. The link that you gave me only gives pictures no way of putting in an order. Is there an email or order form I can use?

 

[eddie49]

They take orders by phone, post, or email ( To: biuro@migomatserwis.pl ).
I can help with writing an email to them in Polish. PM sent.

 

[rotivator]

Thanks for all the info. Just getting used to finding my way around computer. Have now found your email with all the info regarding orders. Many many thanks

 

[Reedweaver]

I am ordering the cheaper relay, do you want me to get two and send on to you rotivator?