BluMaster Cemont Dual Mig 150T

[DAVODLBN]

I acquired a Blumast Cemont DualMig 150T Welder; however, it doesn't work. I suspect the problem is the PCB.

I have looked online for a wiring diagram for this welder but haven't found one.

Would someone on this forum have a copy of the wiring diagram or know where I could get one from? The welder seems too good to scrap.

Regards,

David

 

[Hutcho]

I would check this track and see if it has any continuity to the next point - it don’t look good - also tell us what it’s not doing ? Check simple things like the blue transformer - dry joints

 

[Hutcho]

Looking at at it again they is a few tracks that don’t look good

 

[500e]

Long time ago

Cemont 150 AC/DC ArcoTech inverter any good?

i will have a look on wednesday night as i am away at the min. have you tried to contact cemont for the circuit diagrams? what happened to cause that problem? i dont want it to hapen to mine :D

www.mig-welding.co.uk

 

[eddie49]

Hello David, and welcome to the Forum.

In Posts #10 and #11 of this earlier thread:

Maypole Turbo 120 Mig Welder MP 620 (N412337/89)

I have acquired a Maypole turbo 120 MIG welder from my dad. I have only used arc welding but never a MIG welder. I started the MIG welder even though the pressure in the Co2 was showing zero. It arced once and then the wire feed stoped. The cooling fan is working. I cleaned the gun feed nozzle...

www.mig-welding.co.uk

there are photos of the same "TL5" control board.
This thread:

Wire Feed Upgrade

Hi guys, I have a relatively old basic mig (Kestrel Multimig 100 - no I've never heard of it since I bought it either!!). it hasn't had much service although I did use it about 25 years ago to weld up the front of my wife's mini metro quite successfully. Recently I have started to use it again...

www.mig-welding.co.uk

refers to a "Kestrel" welder that also uses that board, and in Post #1 there is a circuit diagram which shows how the board connects to the rest of the machine.

The first thread linked above explains that, as @Hutcho suggested, the most common issue with welders that have this style of control board is failure of the primary of the small blue potted transformer. The primary is 230v, the secondary is typically 12v or 24v and it drives a small relay to power-up the MIG when the torch trigger is pressed. In this case, a TRIAC is used instead of a relay.

 

[DAVODLBN]

Thanks for everyone's quick reply!

I have tested all the tracks on the back of the PCB circuit board, and they all have continuity.

WHAT'S HAPPENING? I turn on the welder. The fan works, but nothing else works. There is power to the PCB circuit board.

I have tested the diodes on the rectifier, and they seem fine.

I have attached an image here. I circled several elements for clarification, especially two black capacitors (???) and one resistor (???). Does anyone know their classification?

How do you test the blue transformer on the PCB circuit board? I have a Fluke 117 multimeter.

I appreciate everyone's help!

Regards,

David

 

[DAVODLBN]

Hi Eddie49,

I tried your recommendation by bypassing of the Triac as you suggested. When I press the trigger, the feed-wire works. Also I get an arc when I place the wire on the earth.

I measured the two widely-spaced pins (primary) with the reading of 3100 ohms. I measured the secondary pins with the reading of 22.4 ohms.

I am assuming that the blue transformer (see image) is faulty.

Where could I purchase this item?

Again, your help has been awesome and much appreciated!

Regards,

David

 

[eddie49]

Hi Eddie49,

I tried your recommendation by bypassing of the Triac as you suggested. When I press the trigger, the feed-wire works. Also I get an arc when I place the wire on the earth.

I measured the two widely-spaced pins (primary) with the reading of 3100 ohms. I measured the secondary pins with the reading of 22.4 ohms.

I am assuming that the blue transformer (see image) is faulty.

It is good news that using a manual On/Off switch to bypass the TRIAC turns the welder on. That means it basically works and it is worth repairing the fault on the PCB.

As mentioned in my Post #29 of the "Maypole Turbo 120 Mig" thread, I was way too low in my guess about the resistance of an intact primary winding on the small potted transformer. It was not 200 Ohms, nor 2,000, but in fact 2,900 Ohms. That was for a 1.5 VA ( Watts ) unit. At 1.2 VA, the blue transformer in your welder is even lower in power, so a primary resistance of 3,100 Ohms is roughly correct. Therefore the blue transformer is probably not faulty. You could confirm this by applying 230v AC mains to the primary and checking for 12v AC out of the secondary.

If it is good, you could re-install it on the board, and we can continue with troubleshooting. In that Post #29 I had found that a short-circuit in the 2N3055 power transistor was to blame. Since your wirefeed works when the TRIAC is bypassed, maybe some other fault is stopping the welder from powering-up. It could be that the TRIAC itself is faulty, or maybe the TLP3063 optocoupler.

 

[DAVODLBN]

Hi Eddie 49,

Thanks again for your help!

I have replaced the 2N3055 power transistor.

I tested the blue transformer. I connected the primary terminals to 240AC (Australia) and the AC voltage of the secondary was 17AC (see image).

I removed the triac and tested it and the DC voltage was 43v (see image).

I removed the MOC3063 and found that the connections were rusted (see image). This optocoupler may be the problem.

Look forward to your input!

Regards,

David

 

[eddie49]

That is good progress, I think we are homing in on the fault....
These small PCB-mounted transformers are very fragile. Their primaries often burn out, but yours is OK, even when running on the high AC mains voltage that you have in Australia!

The MOC3061 ( or TLP3063 ) optocoupler only uses Pins 1 and 2 for the trigger input, and Pins 4 and 6 are the output signal to switch on the TRIAC. You could put together a circuit to test it, but with those broken pins you probably need to get a new one anyway.

According to Post #6 of this thread:

Wire Feed Upgrade

Hi guys, I have a relatively old basic mig (Kestrel Multimig 100 - no I've never heard of it since I bought it either!!). it hasn't had much service although I did use it about 25 years ago to weld up the front of my wife's mini metro quite successfully. Recently I have started to use it again...

www.mig-welding.co.uk

the TRIAC is a BTA26.600B. It is rated at 600 volts and 25 Amps.
Often used as an On/Off switch for an AC supply, a TRIAC is a pair of back-to-back Thyristors or Silicon Controlled Rectifiers ( SCRs ). These act as diodes, but do not conduct in either direction until triggered by a low voltage or pulse applied to the Gate pin - about 3 volts. As such, they cannot easily be tested with the Diode Test function of a digital voltmeter.

According to the Datasheet:

BTA26-600B Datasheet(PDF)

Part #: BTA26-600B. Download. File Size: 137Kbytes. Page: 12 Pages. Description: 25A TRIACS. Manufacturer: STMicroelectronics.

www.alldatasheet.com

with the metal mounting tab at the back, numbered from the left, the pins 1 and 2 are the two Anodes ( like the contacts of a relay ), and pin 3 is the Gate ( like the coil of a relay ).
The circuit here shows how to test a TRIAC:

How to test a triac.

Testing triac using a multimeter. A multimeter can be used to test the health of a triac. First put the multimeter selector switch in a high resistance mode (say 100K), then connect the positive lead of multimeter to the MT1 terminal of triac and negative lead to the MT2 terminal of triac (there...

www.circuitstoday.com

When triggered on, the TRIAC drives a lamp from a 12v battery. Instead of the 270 Ohm resistor, you could use a second battery, 2 x 1.5v cells.

 

[DAVODLBN]

Hi Eddie 49,

I replaced the BTA26-600B triac and the MOC3063 optocoupler and everything works now.

Thanks again for you help! It was much appreciated.

David