Sharp LC-40LE810UN question

[tibimakai]

Re: Sharp LC-40LE810UN question

OK I will take some more measurements tomorrow.
I had a scope for a while, but I don't know how to use it.
On those two capacitor I measure 29.xV, but I haven't measured with the 18V applied.
The 18V can I leave it on, or just a touch and let it go?

[tom66]

Re: Sharp LC-40LE810UN question

It's not hard to use a scope, didn't you get a Rigol or something? It can be essential for debugging problems.

[tibimakai]

Re: Sharp LC-40LE810UN question

Yes I have a Rigol. I could use it if you help me with it.

[tom66]

Re: Sharp LC-40LE810UN question

Sure, no problem.

Hook up scope to SECONDARY (low voltage) side of transformer tap (any tap will do.)

Ground the ground clip on a ground point (such as the plating around a screw hole.)

Set scope to 5V/div, 100ms/div, auto trigger. Observe any waveform you see, use the save image feature of the scope if it helps. Change taps and see if the waveform changes. It should look a bit like a square wave.

[budm]

Re: Sharp LC-40LE810UN question

"On those two capacitor I measure 29.xV, but I haven't measured with the 18V applied."
Now that does not make sense at all, those two caps in the standby power supply secondary side are rated at 2200uF 16v. Caps would have blown up by now with 29V applied, and beside that, if you have voltage on those two caps, the circuits must be working.
I asked about the reading on post 43.

[tibimakai]

Re: Sharp LC-40LE810UN question

Thanks Tom, I will do that when I get home.
Bud you are right, something it's fishy here, I will double check it again, but I'm almost sure that I have that voltage there. I have answered to your question in #45.
I have reviewed the pictures and I realized that those caps are on the secondary side and I may(most likely) have used the primary ground when I have measured them.

[tibimakai]

Re: Sharp LC-40LE810UN question

Sorry Tom, I don't even know how to set the voltage. I have 0 knowledge about scopes.
Bud, the 18V applied at the high voltage ground and the pin#7 at the IC does not make a change at the two 2200uf capacitors. By the way they are at 0V at both times.

[tibimakai]

Re: Sharp LC-40LE810UN question

Finally I have found the settings for the scope, I will try to measure it.

EDit: No signal at any of the secondary taps.

[tom66]

Re: Sharp LC-40LE810UN question

On all taps?

[tibimakai]

Re: Sharp LC-40LE810UN question

Yes, if I measured correctly.

[tom66]

Re: Sharp LC-40LE810UN question

OK, just to be sure, you had it connected to Ch1, with the scope set to Ch1 switched on, and zeroed ground (press the vertical position dial to zero to get zero ground.)

If you touch the probe with your finger (with ground loose) you should see a wave at approximately 50 Hz appear, it should look like a sine wave.

[tibimakai]

Re: Sharp LC-40LE810UN question

I will have to do it again tomorrow, it's to late now.
You think that at least some of the taps should show something?
Don't forget that I don't have stand by voltage.

[tom66]

Re: Sharp LC-40LE810UN question

I'm trying to figure out if the controller is switching but something's short. If there is something short, you will still get a small output waveform.

[budm]

Re: Sharp LC-40LE810UN question

I would expect to see at least one pulse either at the secondary winding or for the aux winding for running the IC. The detector cannot shutdown that fast. He just have to set the trigger right to catch the pulse.

[tibimakai]

Re: Sharp LC-40LE810UN question

So I have to hold the probe there and then turn it on? Haven't done it that way.
How to use the trigger?

[tom66]

Re: Sharp LC-40LE810UN question

Read, and understand this. http://www.doctronics.co.uk/scope.htm It will teach you a lot.

It is for an analog CRT scope, but it's very similar for digital ones.

[tibimakai]

Re: Sharp LC-40LE810UN question

I can't see any signal, most likely I don't know how to use it.
It has to be on AC coupling or DC?
I went down to 200mV and the "sinus" it was way to small to notice anything.
I don't have Auto Trigger.

[tom66]

Re: Sharp LC-40LE810UN question

Press "AUTO", it's cheating but it should help you get a basic view.

[tibimakai]

Re: Sharp LC-40LE810UN question

Here is a picture with the Rigol that I have(picture is from the web). I have upgraded it to 100Mhz. It doesn't mean anything if I can't use it

[tom66]

Re: Sharp LC-40LE810UN question

I have a Rigol DS1102E, the 100MHz version, which costs only a little bit more than the 50MHz.

Why did you buy a scope if you don't know how to use one? It's only good if you know what you are looking for...