220v to 120v Over voltage protection

[abhi1981]

Hello,
I have a small 220v to 110v converter (approx 50watt). I modified it to give an output of 120v by adding more turns in the secondary.
I want to add an over voltage protection to the output, so that it blows a fuse or something, when the voltage is above 120v .
Any suggestions?
 

[TheMG]

The question is why? It's a transformer, the only reason the voltage would go up is if the input voltage also goes up, which isn't normally a concern. Very unlikely a device rated for 120V nominal would sustain any damage with anything below about 140V, at least in the short term.

If you really do want over voltage protection, the simplest would be to purchase an over-voltage protection relay. They are usually adjustable to some degree so you can set the threshold at which the load will be disconnected.

[coromonadalix]

and  was it not working at 110v before     i have some of theses converters,  i even power 240v stuff at 220v ??   even a 20vac of difference, when stepped down is almost nothing as a difference ??

[Martin72]

I was irritating about the word "converter", when it´s simply a transformer...

[DavidAlfa]

Maybe use a latching relay instead blowing a fuse?
So it self-disconnects permanently until the power is removed.

[fzabkar]

The question is why? It's a transformer, the only reason the voltage would go up is if the input voltage also goes up, which isn't normally a concern.

The situation in India isn't normal.

[james_s]

I was irritating about the word "converter", when it´s simply a transformer...

A normal person has no idea what a transformer is. "Converter" is the correct word for these consumer devices for stepping the voltage up or down when travelling to foreign countries. What is inside them is irrelevant to the consumer, they convert the voltage.

[GigaJoe]

on 240V side, I would add noise filter,  gas discharge tube, and TVS,  req. nominal of course
for overvoltage protection , it would be schematic that drop down 240 to more reasonable ,  compare and trigger relay to disconnect

similar fitters in use for protection high $$$ equipment , for example i have couple one that was to use protect high performance printers around 150K each. (printer , i mean)

[abhi1981]

The converter is for a Yamaha CDC-635 CD player with a sluggish tray.   The player's rated at 120v.
The converter which I have is a 110v one (120v ones are not available), but it outputs 100v when the mains voltage is around 210v. When the voltage is around 230-240v, then it outputs 110v.
What I have observed that at high voltage the tray opens quite normally, and its really sluggish at low voltage ( I have to pull the tray out).
So, that's why I modified the transformer to output 120v. It's now giving an output of 115-120v
But, I'm not very confident about my handiwork  .
Although the converter  is working, but I wanted some protection just to be on the safe side.
The tray is opening now, but its still quite slow. I even changed the motor from a donor CDC-585, but that didn't help.
The rails and gear are all well lubricated with white Teflon grease.

[abhi1981]

The question is why? It's a transformer, the only reason the voltage would go up is if the input voltage also goes up, which isn't normally a concern.

The situation in India isn't normal.

But this is quite normal in India 

[james_s]

The converter is for a Yamaha CDC-635 CD player with a sluggish tray.   The player's rated at 120v.
The converter which I have is a 110v one (120v ones are not available), but it outputs 100v when the mains voltage is around 210v. When the voltage is around 230-240v, then it outputs 110v.
What I have observed that at high voltage the tray opens quite normally, and its really sluggish at low voltage ( I have to pull the tray out).
So, that's why I modified the transformer to output 120v. It's now giving an output of 115-120v
But, I'm not very confident about my handiwork  .
Although the converter  is working, but I wanted some protection just to be on the safe side.
The tray is opening now, but its still quite slow. I even changed the motor from a donor CDC-585, but that didn't help.
The rails and gear are all well lubricated with white Teflon grease.

That's strange, I would expect the power supply in the unit to be regulated, is an unregulated supply used for the tray motor? Have you checked the voltages inside the unit? If your line voltage varies a lot they make voltage stabilizers that have a tapped autotransformer and a circuit to automatically change taps as needed.

[abhi1981]

The tray motor gets its power from a motor controller TA7291P, which is controlled by another IC.
I didn't check them. Maybe they are defective, but as long as I don't have a replacement at hand, there is no point testing them. They are not available locally, and nobody will ship to India from abroad. The Aliexpress ban has made things worse.
The tray is kind of working now, so I didn't dig deep into it.

[IanB]

The situation in India isn't normal.

Looks like the internals of any typical computer program    The difference is, the internals of a computer program are not on display to the general viewer.

[james_s]

The tray motor gets its power from a motor controller TA7291P, which is controlled by another IC.
I didn't check them. Maybe they are defective, but as long as I don't have a replacement at hand, there is no point testing them. They are not available locally, and nobody will ship to India from abroad. The Aliexpress ban has made things worse.
The tray is kind of working now, so I didn't dig deep into it.

Where does the power from those ICs come from? Have you checked the electrolytic capacitors in the power supply section?

[Martin72]

The Service Manual for this player is avaible for free on electrotanya:

https://elektrotanya.com/yamaha_cdc-635_cdc-95_cdc-96.pdf/download.html

This player was with several mains inputs avaible, most universal the "R" version from 110V to 240V switchable.

[abhi1981]

I have the service manual.
My player does not have the multi input option for mains.
I checked the two large capacitors, they were okay. Being Rubycons, they should be okay I assume that the others may be okay too.

The converter hack seems to working. The tray is working now.
It seems to be more of a mechanical issue. Even with the belt removed, the tray movement is not free.
It requires considerable effort to move, even after lubrication.
Maybe its a design flaw. They should have used a bigger motor for that kind of load.
One thing I noticed, that if I use a thicker rubber belt, then the motor doesn't move at all, whereas it works fine with a thinner belt.