[JQ_Quint]

Ok so I've already posted this in the chinese router forum page with no response as yet so thought i'd ask for help here too:



After tripping over the mains 240v cable on my JCUT 6090b (cnc chinese router) and hearing it spark at the kettle socket end (machine end) it now keeps blowing fuses...

Initially was in the 5v-12v transformer (see image 1) at the 3amp glass fuse, but since changing the mains 5amp wall fuse to 3amp thats the one that keeps blowing now on every fire up (soldered a new glass 3amp into the transformer) .

The kettle socket end did come loose hence the initial spark but is fully inserted now.

Also whats odd is at the point of power up its the mains 240v live into the transformer that flashed when i power up (which then blows the mains fuse)

If I disconnect the 240v live into the transformer the machine powers up (vfd and drives are all energised and stay energised).

Any help appreciated - i am an engineer but not an electrical engineer

Blowing Fuses After a Power Outage-image-1-jpg
Attachment 408102



Circled point "A" is where i now get a flash at power up. Disconnecting the live and neutral here prevents the fuse blow (so drives see power ok)
, but obviously no power now to spindle control board and smooth stepper

My circuit - although as per with these chinese machines its not 100% accurate, for example
Attachment 408104



thanks for reading..

[john-100]

two things I would do

first check the wire circled in the photo has bootlace ferrule fitted correctly
you may find the ferrule is gripping the insulation and not making a good connection to the copper wire

remove the 3A mains fuse you replaced the 5A fuse with and replace it with another 5A fuse

transient voltages produced by a poor mains connection can result in damage to switch mode power supplies
like the one in your photo

even if you get the 5V power supply going now I would replace it for long term reliability

John

[JQ_Quint]

HI John,

Thanks for replying..

I'm back n the workshop tomorrow so I'll check the connection circled, it definitely sparks there, but its been on and off a few times so im sure its tight but i'll check anyway.

With regards to replacing the mains plug 3a back to the original 5a, I gues the only pain with this is that im then blowing the glass fuse in the transformer which is soldered in so a pain to replace.. But again i'll try too when i check the wiring..

Jamie

[JQ_Quint]

two things I would do

even if you get the 5V power supply going now I would replace it for long term reliability

John

Would this be suitable John:
https://www.ebay.co.uk/itm/DC-3-3V-5...r=451076083336
(The 5v 3a 15w version)


Difference being mine is 25w, but this one from makershut is only 15w ??? Will this give me problems?

Also another query- my psu is labelled as having 12v output also? I'm going to trace the wires tomoz but im sure they only go to smooth stepper & spindle control board and as such are only 5v, so Im confused why its labelled as 12v also with seemingly no 12v outputs ??

Attachment 408156

[john-100]

your photo does indicate its a dual output power supply - 5V @3A & 12V @1A

after a quick search some thing like this looks like could replace it

https://www.ebay.co.uk/itm/30W-Dual-...4g2W:rk:4:pf:0

I guess the 12V output could be to power a 12V fan ?

John

PS
on second thoughts

if the spindle control board is something like CNC4PC's C11

the power supplies 12V output could be powering the PWM to analogue 0-10V converter

[JQ_Quint]

your photo does indicate its a dual output power supply - 5V @3A & 12V @1A

after a quick search some thing like this looks like could replace it

https://www.ebay.co.uk/itm/30W-Dual-...4g2W:rk:4:pf:0

I guess the 12V output could be to power a 12V fan ?

John

PS
on second thoughts

if the spindle control board is something like CNC4PC's C11

the power supplies 12V output could be powering the PWM to analogue 0-10V converter

Hey John,

So just tested the power supply with an independent 240v power supply as to separate possible issues that could be causing the problem before the PSU AND it still blows ….

Looking closely at the PSU there is a capacitor and resister that have been arking so i'm hoping that's the cause.

So I need a new PSU, oh and your 100% right just traced a 12v lead to the CNC4 spindle control board, like I said in my initial post that circuit diagram has missing elements which in this case is a 12v feed from the psu to the control board (which confused me)…

So with regards to the link you sent me, yes that's great but its in Hong Kong, which is stating an end of Jan delivery so I'll look see if I can find a uk supplier (unless your aware of one) , failing that I'll order that one.

Thanks for your help John... I'll keep you posted.

[john-100]

now you know what's faulty it is a step forward

as ebay searches for UK only " Dual output 5V 12V Switching power supply " find nothing

you could search for two single output supplies - one 5V and one 12V

possibly starting with

https://www.ebay.co.uk/itm/DC-3-3V-5...AAVg:rk:2:pf:0

John

[Toinvd]

You might find a suitable power supply from a old 3.5" hard disk. 12Volt on yellow, and 5 volt on the red wire Black is ground ( 0 volt )

[john-100]

hard drive power supplies like this -

https://www.ebay.co.uk/itm/HDD-POWER...JClM:rk:2:pf:0

Attachment 408308

will work provided the spindle speed control input is isolated from the mains supply unlike the FC250J board used in my minilathe !

the hard drive power supply 5V & 12V outputs have a common negative connection

the original power supply will have isolated 5V & 12V outputs

John

[JQ_Quint]

hard drive power supplies like this -

https://www.ebay.co.uk/itm/HDD-POWER...JClM:rk:2:pf:0

Attachment 408308

will work provided the spindle speed control input is isolated from the mains supply unlike the FC250J baord used in my minilathe !

the hard drive power supply 5V & 12V outputs have a common negative connection

the original power supply will have isolated 5V & 12V outputs

John

I gone ahead and ordered the one that you suggested from China John, due mid late Jan unfortunately so I'll update once fitted, fingers crossed eh !

[KH0UJ]

A PC Power supply is sufficient enough to power your needs, you can salvage it from old PC units, available voltages are 3.3V ,-5V,-12V(which you dont wanna use) +5V and +12V, just put a jumper on the green wire (PS-ON) on the 24 pin socket to ground, so every time you put power to the 220VAC it automatically powers ON at the secondary voltages that you needed. I bet PC power supplies are quite common in your area but the most thrifty move is when you have it with you just laying around, convert it, take out all the unnecessary wires that you dont wanna use, dont worry about the circuit protection, a generic power supply is a switching power supply, which means it`s an over current protected, over voltage protected, short circuit protected design, it will just shut down whenever it experiences a short on the load either on the output voltages. it will automatically turn back ON if the "short" is taken out, all you need to do is plug / unplug the 220V input to reset it to power it back again.