What frequency limit I should plan for when choosing oscilloscope for TV repair?

[lookimback]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

Did you open it up to verify if the LINE, Neutral, and safety GND are wired properly?
Verify if the the Neutral goes straight through from the AC plug to the outlet Neutral, and the fuse in on the line side not on Neutral.

I haven't opened it yet, but I did use my meter to probe the AC plug and the outlet. I get no continuity from AC plug neutral to outlet neutral, no continuity from AC plug Line to outlet Line, and I do get continuity from AC plug ground to outlet Ground.

[lookimback]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

Yup, they got the fuse on the neutral side. I'll change it.

[budm]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

The wiring should be the same as the one in the link (The main fuse should be right at the incoming AC LINE instead of at the output).

'I get no continuity from AC plug neutral to outlet neutral, no continuity from AC plug Line to outlet Line,' That does not sound right.

Never mind, you have the isolation type.

[lookimback]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

Mine is isolated.

[budm]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

Mine is isolated.

It's good that it is isolated as verified.

[tom66]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

Variac outputs are not regulated. The voltage scale depends on the input voltage

[stj]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

stick a pair of these on it.
http://www.ebay.com/itm/331346760410

[lookimback]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

Variac outputs are not regulated. The voltage scale depends on the input voltage

Ok, that makes sense. Thanks.

stick a pair of these on it.
http://www.ebay.com/itm/331346760410

I've been looking for something like that but the problem is the voltage range. I need something with 0 to at least 150 VAC range. I'm interested in something which also has an ammeter in it.

Something like one of these would be very useful if the voltage range could be modified somehow.
http://www.ebay.com/itm/100A-AC-Digi...0AAOSwd0BVqvY4

http://www.ebay.com/itm/AC-Digital-A...wAAOSwrklVbDSX

[stj]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

you can probably modify the ones i linked.
the problem is any meter is going to be powered by the line your sensing.
so at some point there wont be enough voltage to drive the meter.
unless you mod it for a seperate power source.

the one i linked is going to be fine on your input though.

[lookimback]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

So, if I modified it for a separate voltage source to drive the meter, it would probably work for lower voltages?

[stj]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

it's listing a 1v sensitivity,
so i would say if it had seperate power you could probably go 1-500v!

so where to get the power - more importantly how.
i dont like the idea of just grabbing the mains - it kind of defeats the isolation.
maybe a small isolating mains transformer.

you really need to get one and draw up a schematic of the power part of it to see the best method.
-------
btw, it's probably going to need the supply voltage to be higher than or equal to the input it's metering

[vinceroger69]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

stick a pair of these on it.
http://www.ebay.com/itm/331346760410

Does it go to 600v the title says it does but when you read the specs it says 60-300v ?

[stj]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

who knows.
i'v seen the 0-30v model being tested, the range seemed related to the power driving the led segments.

it's using a resistor and capacitor to drop the incoming voltage.
maybe if you mess with them you can lower the range to 30-150v for example.

[lookimback]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

it's listing a 1v sensitivity,
so i would say if it had seperate power you could probably go 1-500v!

so where to get the power - more importantly how.
i dont like the idea of just grabbing the mains - it kind of defeats the isolation.
maybe a small isolating mains transformer.

you really need to get one and draw up a schematic of the power part of it to see the best method.
-------
btw, it's probably going to need the supply voltage to be higher than or equal to the input it's metering

I definitely wouldn't use the mains for power because I expected it would defeat the isolation. It seems there would have to be a tap on the secondary I could use.

[stj]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

http://www.jammarcade.net/cheap-voltage-display/
review of the one for 0-30v

[lookimback]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

What's wrong with this picture?

[budm]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

You should draw out the connection before fixing it. May be they have the fuse on the output winding like the one used in STACO.

[Agent24]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

Nothing is wrong, the behavior of the device is consistent with the word "China" on it.

Or maybe the lamp is before the fuse, showing you when the device is plugged in and has power at any time. That could be kinda useful actually, in an over-paranoid way.

[lookimback]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

You should draw out the connection before fixing it. May be they have the fuse on the output winding like the one used in STACO.

It's actually connected in series between the switch and the transformer. I was mistaken earlier when I said it was on the neutral line. With no current flowing, there is very little resistance on the winding, so that made me think the fuse was on the neutral.

Nothing is wrong, the behavior of the device is consistent with the word "China" on it.

Or maybe the lamp is before the fuse, showing you when the device is plugged in and has power at any time. That could be kinda useful actually, in an over-paranoid way.

I needed a good laugh, and that did it. I could see that being useful as an indicator, as long as the switch doesn't eventually blow up like the one in my coffee maker did.

I'm thinking about replacing the fuse with a panel mount circuit breaker too.

[stj]

Re: What frequency limit I should plan for when choosing oscilloscope for TV repair?

that's actually smart because it stops people changing the fuse with the power on by mistake.