Author Topic: Beginner question: Repair damage and convert from 110v to 230v  (Read 718 times)

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Offline as2003

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Beginner question: Repair damage and convert from 110v to 230v
« on: January 06, 2018, 05:14:49 pm »
My wife bought a laminator from Amazon US (rated for 110v only) and when she plugged it in, in Australia, it promptly went pop!



In the picture above, you can see there's a ceramic capacitor that's blown up. I plan to replace that, but I have a few questions:
  • Why is the symbol under the blown capacitor a diode?
  • Why didn't the fuse blow and protect the circuit from damage?



I also noticed that an electrolytic capacitor on the board is damaged. Could that have caused the circuit to fail or was it definitely just the 230v?

Once I've repaired the damage, I want to convert this thing to run on Australian mains voltage.

I guess the best solution is to replace the transformer with something rated for 230v, with a similar output as the original, but let's say this is a post-apocalyptic scenario and I didn't have access to any replacements, could I double the number of input windings? Or halve the number of output windings? Or something in-between?



(More photos)
« Last Edit: January 06, 2018, 05:30:20 pm by as2003 »
 

Offline Inverted18650

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #1 on: January 06, 2018, 05:26:38 pm »
Hey mate,

Someone will probably make things much more clear for you shortly, but the little blue thing is normally an NTC (or MOV). The NtC is kind of a variable resistor that limits the inrush current at power up. As they warm up their resistance changes and they allow more current to flow. Here, the NTC blew and the cap after it popped as well.  If you swap them out, clean the tracks, you will probably be okay edit: as long as you don’t try to use it up at 220 again...
« Last Edit: January 06, 2018, 05:37:41 pm by Inverted18650 »
 
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Offline ataradov

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #2 on: January 06, 2018, 05:33:46 pm »
Cap looks mechanically damaged, possibly from the drop.

There is no easy way to convert without changing the transformer. EDIT: Although it looks like the transformer has 4 pins on the primary side, which may mean that it is switchable with some minor board surgery. But if that laminator includes some sort of heating element, then it is probably powered from mains, which makes things much more complicated.

Can you read the markings on the blown part?
« Last Edit: January 06, 2018, 05:37:16 pm by ataradov »
Alex
 
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Offline Ian.M

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #3 on: January 06, 2018, 05:46:06 pm »
However converting it for 230V operation wont be simple or easy.  Odds are it uses a 120V heating element, run direct from mains via a TRIAC, and both would need to be replaced to convert it.   The transformer powering its temperature controller would also need to be replaced* and most likely the motor as well, as there is a high probability its also mains powered.   The expense to do so will almost certainly exceed the cost of a new 230V laminator.

The alternative of a 230V to 110V transformer is also expensive and probably not economic unless you have a number of 120V appliances that can share the same transformer.

* Although the primary is labelled as 120V on pins 1 and 4, there is no indication that it has two windings in parallel that could be rewired in series for 220V - 230V operation, as that would be indicated by something like:
120V:  (1+2)-(3+4)
220V: 1-4, (link 2-3)

Edit: the board is actually laid out for 220V: 1-4, (link 2-3), so probably they fit a dual 110V (or 115V) primary transformer for the non-US model
« Last Edit: January 07, 2018, 04:59:40 pm by Ian.M »
 
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Offline Inverted18650

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #4 on: January 06, 2018, 05:53:32 pm »
I see four little diodes on the bottom so it looks like they are rectifying the AC after the trans. You may be able to feed a dc voltage directly into that point as well. Looks like 10.5VAC out of the trans..less the diode drop, maybe 8-9VDC Power? This could be very incorrect so wait for the pros to follow up. Check the part number on the SOT 23-3 package and see if it’s a little voltage regulator or a switching tranny...if it’s a 5V regulator, try to feed a 9V battery into the input and see what happens..
« Last Edit: January 06, 2018, 05:56:59 pm by Inverted18650 »
 

Offline Nusa

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #5 on: January 06, 2018, 05:55:28 pm »
My wife bought a laminator from Amazon US (rated for 110v only) and when she plugged it in, in Australia, it promptly went pop!

In the picture above, you can see there's a ceramic capacitor that's blown up. I plan to replace that, but I have a few questions:
  • Why is the symbol under the blown capacitor a diode?
  • Why didn't the fuse blow and protect the circuit from damage?

I also noticed that an electrolytic capacitor on the board is damaged. Could that have caused the circuit to fail or was it definitely just the 230v?

Once I've repaired the damage, I want to convert this thing to run on Australian mains voltage.

I guess the best solution is to replace the transformer with something rated for 230v, with a similar output as the original, but let's say this is a post-apocalyptic scenario and I didn't have access to any replacements, could I double the number of input windings? Or halve the number of output windings? Or something in-between?
I presume a North American plug was on the device? Did the wife use some kind of adapter to plug it in?

1. It's not a symbol for a diode. It's one of the symbols used for a varistor.
2. Fuses blow from high current, not high voltage.

That cap looks like mechanical damage from a screwdriver or something. Rated at 25V, so it's clearly on the DC side of the transformer. Should be replaced if you're repairing the board. No, you can't pin the blame on it for operator error.
 

Online coromonadalix

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #6 on: January 06, 2018, 11:12:55 pm »
In electronics you will learn with smps or standard psu  the fuse will be the last to blows ....   you will have to rebuild the psu,  the main transistor(s), rectifier diodes,  the protectors, maybe pcb traces ...  if your lucky  there wont be too much damage ...

Use an 220-240v to 120v step down transformer to drop the voltage next time. 

Not a thingy winky adapter converter sold on ebay ....  since a transformer is an inductive load, some of the converters dont work very well ...

Or trying to source an 230v to your output voltages for the pcb who respect the wattage printed on the equipment ???  it says 10.5 vac at 120 ma for the output for total of 1 .26 watt,  should not be hard to find, the size seems standard too ...
 

Offline jolshefsky

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #7 on: January 07, 2018, 01:40:14 am »
Odds are it uses a 120V heating element, run direct from mains via a TRIAC, and both would need to be replaced to convert it.

It may not be that hard: one I have works off mains (U.S. version; in U.S.) and I think it has two resistive elements in parallel implying series would be for 220V. Looking at it now, it has four or so with what appears to be center-tapped connections, presumably for the high-low power control. There's also a relay which is probably the heater switch.

Although the primary is labelled as 120V on pins 1 and 4, there is no indication that it has two windings in parallel that could be rewired in series for 220V - 230V operation, as that would be indicated by something like:
120V:  (1+2)-(3+4)
220V: 1-4, (link 2-3)

Maybe ... the transformer says 120V which implies to me it doesn't have the dual-primaries, but you might get lucky. Regardless, that transformer is just for the control electronics and could probably be swapped for a 220V version without much trouble (common form factor) or even for external power from a wall wart supply (if you want to get ugly).
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Offline Nusa

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #8 on: January 07, 2018, 04:40:58 am »
Listen to Ian's response above. It's pretty clear from the pictures that the motor is also mains-powered. You can see the motor relay and connector right next to the mains input in one shot. I'd call that uneconomical to convert. So unless you've got an external 220-110 isolation transformer, there may not be any point to fixing it.
 
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Offline Rasz

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #9 on: January 07, 2018, 05:40:55 am »
directly mains powered components + Amazon basics laminator is $17.88, into the bin it goes.
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Offline as2003

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #10 on: January 07, 2018, 03:26:30 pm »
Thank you all for the replies. I've learned a lot already.

I expected it wouldn't be economical to repair, but I'm planning to use this as a learning experience more than anything else. I was hoping I'd be able to repair the damaged components with parts from my salvage bin, or things from my local maker space, but based on the above, it's clear I need to first try to map the circuit and understand it properly.

Unless I made a mistake, the triac has a VDRM of 800v, so I assume that'll be fine.
 

Offline Ian.M

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #11 on: January 07, 2018, 04:27:08 pm »
Looking at the extra images on Google, there's only one brown (Line) wire going to the board, at one end of the fuse with no branch tracks, so the varistor must be after the fuse.  It looks like its across Line and Neutral, and its purpose would be to shunt spikes that could otherwise damage the TRIAC and control circuit.  At the normal 120V supply voltage it normally would be non-conducting.  It would be specified to conduct at about 200V.  As it normally doesn't conduct you can clip it out, (and keep it - you need the part number), clean the burn marks off the board, and check the fuse - if its O.K, the laminator should then run from 120V, unless the transformer or motor have been damaged by the overvoltage.   If it runs, order a new varistor (post a closeup of the blown one's part number if you have difficulty matching it) and fit it otherwise the laminator will probably die an early death due to mains spikes.  If it doesn't run, its B.E.R.
« Last Edit: January 07, 2018, 04:32:50 pm by Ian.M »
 

Offline Armadillo

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Re: Beginner question: Repair damage and convert from 110v to 230v
« Reply #12 on: January 07, 2018, 04:34:04 pm »
Regarding the fuse, it didn't blow because your wife merely plug it into the power source and did not turn on the switches, so only those components before the OFF switches suffered the damage. I imagine there are 3 switches, one for the heater, one for Power on, one for forward and reverse but there are so many laminators in the market and I could simply be wrong here.

Conversely, the fuse should be the first to blow as it is designed to protect the circuit, not any later.


 


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