Purpose of fuse in televlision

[micky]

I took apart the television I've posted about and there is a fuse on the power supply board and it's blown. It was blown (and the home circuit breaker was tripped at the same time it iseems) when a helpful neighbor plugged the 110v tv straight into 220.

What is the purpose of the fuse: To keep a short circuit in the power supply (or other part of the tv) from pulling too much current, melting the wire's insulation, and starting a fire?

Or the opposite, to protect the TV from surges.

It will be hard to find another fuse. It's a small size ceramic fuse. I can post the size after I f ind a lamp and a magnifying glass, but it's probably 2 or 3 amps, right? (Are all ceramic fuses slo-blo?)

If the purpose of the fuse is only to protect the tv, I'm willing to take the risk, wrap the fuse in tinfoil and put it back together.

If it's to avoid a fire, then this is a 110v tv in a 220 volt world, supplied by a step-down transformer of limited amperage. 500 watts. (It gives the same wattage for both directions.) Surely even a cold short in the tv when the maxiumum supplied power is I guess about 5 amps would not be anywhere near enough to start a fire.

Right?

The other possibility is to wrap the fuse in foil, decide if it works or not, and leave here (where it is too cold for me and too rainy) and come back after I buy the right fuse in a city. What are the odds it will fail in the next 3 week? That requires putting the tv back togehter an extra time, but that's not so bad.

We are 50 miles from nowhere down a rainy winding road.

[micky]

It seems to be 8 amps. I didn't think they used them that big, but otoh it's 40amp led screen tv.

We are 50 miles from nowhere down a rainy winding road.

Tomorrow we can make some phone calls trying to find a place closer than

60 miles, but you know as well as I that even if the ad says Electronicsm they probably won't have it, and real reapir stores are few and far between. And I don't want to spend tomorrow night here. I want to fix this and be done.

[trader_4]

A 40 amp TV?

Probably can find it or one close to it that will work on Ebay, but that won't be by tomorrow.

I would think the fuse helps both ways, without the fuse the UL and any other certification is out the window.

You could certainly bypass the fuse to test and see if it works or not before all the worries about the fuse. If it doesn't work, that's pretty much the end right there.

[danny burstein]

In [e-mail] micky [e-mail] writes: [snip]

About 3 decades (obligatory where does the time go?) ago my large (for the time) Sony tv just died. I took it apart and yes, there was a fuse in the power supply that had blown.

It was a simple automotive type ACG glass fuse, so the next time I was near a car supply place I picked up a set of them.

I figured there was enough of a chance this was a "once off" fuse failure that (aside from my time...) it was worth spending $2.50 or so to check it out.

(Alas, that second fuse blew, too).

Anyway, that might be an option for you. Depending on how the wiring posts are, you might be able to hook up a similar automotive fuse holder and, well, fuse... and see what happens. Probably $10 or so of parts nowadays.

[Dean Hoffman]

What's ahead of the tv in the wiring? Could you put the same amperage fuse the tv has somewhere upstream in the circuit?

[Mike Coon]

You cannot mean 40 amps, surely? Even at only 110 volts that is still quite a powerful heater! 40 inches, perhaps?

[Clifford Heath]

To stop your house burning down.

It won't be hard to find another fuse, but you might have to pay for postage.

The fuse will usually blow after something else in the TV has failed. If you bridge the fuse, it will fail harder.

The transformer has limited amperage because if you overload it, it will burn out or catch fire.

Get a proper fuse. Buy two, because the first one will probably blow due to the fault that blew the first one. Use the second after you've fixed that fault.

CH

[Clare Snyder]

We KNOW what the "initial fault" was - overvoltage. IF the fuse blew fast enough it may have prevented a seconsry fault. a

7 or 8 amp standard automotive fuse in an inline holder temporarilly connected to the old fuse holder should tell you if the TV itself is unharmed. Or get a set of "test leads" with 'gator clips on each end and jumper the fuse in that way.

[micky]

This seems very important. If there is one that's shorted, it will just blow the fuse over and over, and if I've bypassed the fuse....would that allow enough current to start a fire?

The board has a fee parts that might be a MOV. They are labeled CY101..., TH101..., UA101 and CP101. There is only one of the last two. Are any of these usual abbreviation for a MOV? I've been looking online for a list of abbreviations that includes these, no luck so far, quicker to ask you, Bob (and others).

Retirednoguilt was kind enough to post Power supply on ebay shows a fuse in the photo :

that looks just like her power supply. --- Surprising since I had found this video of someone repairing the PS on supposedly the same model and the boards look entirely diffferen -- [Insert url here]

I'm the second or third person she's had look at it. It's too big and heavy to take to a shop, so if I bypass the fuse and fail to note a shorted MOV and it gets worse, I think she will just take her loss and buy one.

References to previous thread. The TV has HDMI input (3 interfaces!), but when she lived in Baltimore she was streaming from Amazon, and I think that was her current plan. Although I don't understand how. The manual says "INPUT ? Repeatedly press to change the source you are viewing (ANT/CABLE, VIDEO 1, VIDEO 2, ColorStream HD1, ColorStream HD2, HDMI 1, HDMI 2, HDMI 3, PC)."

Colorstream is their name for separate red, blue, whatever color input. Component! That's it. She can't use that.

Video1 AND 2 are composite, she can't use that.

PC IN ? For use when connecting a personal computer. When she lived in Baltimore her PC was in another room and I don't think there was a wire connecting them. I've written her son to try to find out what she is talking about.

[micky]

So 8 is not unusual. Good. I thought it would be 2 or 3 but it seemed to say 8 on it.

I bring jumper wires with me when I travel. For a second I thought I had fuses in my trunk, until I remembered the car is in the USA and this is a rental. I could borrow a fuse from the car , but then I'd have to find a replacement for that. Not that much easier.

BTW it appears that the guy she knew, who iiuc mostly fixes washers and dryers, opened it up and looked and was mistaken he said, as reported, everything was good. Of course ceramic fuses usually don't show when they are blown.

[Jeff Layman]

(what url did you forget to insert?!)

Did you not read the warning above the fuse on that PCB? "CAUTION: For continued protection against risk of fire replace only with same type and rating of fuse". I don't think it could be any clearer.

Out of interest, is it usual in the US to spec a 240V fuse for use with a 120V supply?

[micky]

Ok, guys, I jumpered the fuse holder with a store-bought 10" jumper wire and got a big spark (even before I tried to turn the tv on. I guess I should have anticipated that.)

I thought that was bad until I thought, Well, it uses almost 8 amps and maybe the alligator clips didn't make a good connection.

So used all three jumper wires and this time no spark, just smoke. :-)

From one of the diodes, based on the brown spot next to it and the swollen diode.

Plus the alligator clips at one end of two of the jumper wires fell off!

So now it's on to a new board.

The board is discontinued of course, but there are lots for sale at various places, all about 40 dollars. Whether they are new, "reconditioned" or used, it's okay by me.

The part number is Toshiba PK101V0830I

But what would be great is to find the 220v version of this. So how would I find what the part number is for the 220 volt version of this.

I wrote Toshiba to ask what the partnumber would be for 220v, but I think I wrote Toshiba USA. I can call Toshiba in the US Monday at

8AM. Will they know or should I call some European repairman? I haven't found a tech support page for anywhere in Europe yet. It looks like I have but then the page is about all of Toshiba, not just tvs, not just consumer goods,

Would Toshiba use the same tv model# 40RV525U for its 220volt model? I doubt it, and I can't guess what it would be.

What should I do next? (Helpful answers only, please.)

[Dean Hoffman]

Has the TV been used on the same circuit in the past with no problem? It's not a voltage issue if yes.

[trader_4]

What's the cost of a used 240V European TV at the local thrift store, European Craigslist, Ebay, etc?

[Ralph Mowery]

In the US fuses for the plug in devices like lamps and TV sets are usually rated for 250 volts. It is fine to use a fuse rated for 250 volts on the 120 volt devices. Most of the house wiring is for 120 volts for the common plug in wall sockets.

There are some fuses rated for around 25 volts (forget the exect voltage) that are made to use in the older cars that operate on 12 volts and maybe 24 volts DC.

The reason for a voltage rating on a fuse is that if a higher voltage is used it may arc over and not actually cout off the power. A fuse rated for 10 amps will open at around 10 amps no matter what the voltage is as long as it is low enough not to arc over.

[micky]

Who knows! With all the radiation I've gotten ever since I used that off-brand fuse, I can't tell my right hand from my right hand.

No. Warnings are for grown-ups.

Most fuses go up to 250, don't they?

[micky]

No, she just moved here from America. And the neighbor before she knew it plugged it into the wall with just a plug adapter. Maybe he thought tvs were like computers and usb chargers.

[Dean Hoffman]

Amazon has travel converters for around $40.

[micky]

I was going to find the url before posting. Failing that I tried just now.

Someone messed with my Firefox and made Bing the default search engine!! I sure didn't do that.

So I thought if I went back to google I'd find it. It was the second or third hit when I first looked, searching on the TV model number. Now I can't find it at all. I thought it int eresting becaue the board didn't look at all like the one in the ebay ad, and maybe someone wrote him or he noticed he had the wrong model number and he changed it, so I can't find it. Who knows? It was the wrong video anyhow.

[micky]

That's a good idea, at least in general, but the closest thrift store to her seems to be about an hour away.

3 hours away, I walked by one and went in and it was all clothes.

I wrote Toshiba so instead of calling them on Monday, I'll wait until Tuesday or Wednesday to call. Maybe they'll write befoee then. I'd give 2 to 1 odds they won't know the part number off the 220v board.

The rush is over becauase it didnt' get fixed today and I'm leaving tomorrow (I had hoped to leave today) . She has a friend in of all places the same city, Baltimore, where the board that RetiredAndNotComplaiingabouit was for sale from, who is coming to viist her in about 3 weeks. So there is plenty of time to buy it (He has 7 of them**) and she can bring it, and I'll come here for a day and put it in. She alr eady has a transformer she's not using, I forget whh.

I assume is no chance the 220volts damaged the main board or the little boards that controls are attached to. If it did, it's a waste of 40 dollars.

When she was in Baltimor e she streamed from Amazon, didn't require any other hardware. I don't know how that could be -- it's a good tv but not a smart tv and doesn't have wifi. It has computer input but it looked complicated. if a cable was involved, she probably brought it.

-- so I wrote her son. Otherwise she can pay for cable.

**How does someone end up with 7 of something like this?