   noob oscilloscope question
  hi   this is off topic BUT I do some lcd monitor repairs, mostly back light problems and power supplies ect. I have been doin mostly bad caps, fuses ect.and now I want to get a little deeper into the repair of them and want to buy the cheapest scope I might need for this work.  I dont plan to use it for anything else so if you could help me with the probable bandwidth I might encounter I would app it a lot.  These are 15inch to 26 inch lcd monitors and some lcd tv,s too.   thanks tom   hi again    I just added this part. I won,t be getting into the video part of the repairs but more into the power and back lighting portions because of parts and time. I,m pretty much going for the easier fixes that are more obvious.I don,t plan to get into the video output portions of the units.  Sorry I didn't say this at the start.[Edited by - oldoldoldman on May 30, 2009 8:07:11 PM]
  Don't know the specifics of vga/hdmi but I'd guess that a 60-100MHz scope might work for most repairs. Probably want to up the scope bandwidth as you get to bigger resolutions and standards such as hdmi. Keep in mind that for signals over 100MHz, an active probe is pretty much required and those are expensive. Also, if you get an (X)MHz scope, does not mean that you'll be able to see an (X)MHz square wave, you have to keep in mind all the extra harmonics of signals and that will push the required o-scope bandwidth up.   ;Quote:Original post by oldoldoldmanhi   this is off topic BUT I do some lcd monitor repairs, mostly back light problems and power supplies ect. I have been doin mostly bad caps, fuses ect.and now I want to get a little deeper into the repair of them and want to buy the cheapest scope I might need for this work.  I dont plan to use it for anything else so if you could help me with the probable bandwidth I might encounter I would app it a lot.  These are 15inch to 26 inch lcd monitors and some lcd tv,s too.   thanks tomI'm curious, what kind of repairs are you doing that would require a scope?The tasks you described can be handled with a good multimeter or two.I can't imagine anyone doing more in-depth repairs unless you are an EE with some detailed knowledge of the hardware.  In that situation, you would already know what kind of scope you should buy.   ;  I use scopes as cracked out volt meters. A 4 channel scope is invaluable for debugging a serial comunication bus. So i'd recommend at least a 4 channel, and preferably one that has a webserver so you can log in from your computer and download/view information. Good for posting on forums with questions about what you see. Or asking the manufacturer.   ;  Since I'm in my 60s and don't have any training you have a good point.   I have been fixing monitors by comparing them with each other, that is one that is working with one that is exactly the same but is not working and slowly running down the bad parts that way.  I found out that I SEE a lot more with a good multi meter (FLUKE) than with a cheap one.  I keep finding new parts that I want to see into what they do and think I can learn to use a scope on my own time with time.   What do you think?   ;Quote:Original post by bzroomI use scopes as cracked out volt meters. A 4 channel scope is invaluable for debugging a serial comunication bus. So i'd recommend at least a 4 channel, and preferably one that has a webserver so you can log in from your computer and download/view information. Good for posting on forums with questions about what you see. Or asking the manufacturer.Sounds like a waste of o-scope resources if you ask me...If your debugging only concerns digital data ie you only care about 1s and 0s, then you should instead use a logic analyzer, you can get like 32+ channels and it should have a PC interface. Shoot, you can probably find a few diy logic analyzer projects online that can sample at a few megahertz.O-scopes are for the analog waveforms. In the digital world, that means that o-scopes look at the rise and fall times, whether there is ringing, etc. A 4-channel o-scope will obviously cost more than a 2-channel and most times you can get away with only 2 channels. By the way, I REALLY DONT recommend getting a one channel scope.Quote:Original post by oldoldoldmanSince I'm in my 60s and don't have any training you have a good point. I have been fixing monitors by comparing them with each other, that is one that is working with one that is exactly the same but is not working and slowly running down the bad parts that way. I found out that I SEE a lot more with a good multi meter (FLUKE) than with a cheap one. I keep finding new parts that I want to see into what they do and think I can learn to use a scope on my own time with time. What do you think?If you really want to learn to use a scope, buy a few opamps (741, NE5532, etc) and build a few analog circuits that work in the audio range. This should get you acquainted with the oscilloscope and what various knobs and buttons do. The last thing you want to do is fry a channel on your scope or the device under test because you connected something wrong (eg high voltage signal for backlight) on accident; I killed an RC car electronic speed controller that way.;Quote:Original post by oldoldoldmanSince I'm in my 60s and don't have any training you have a good point.   I have been fixing monitors by comparing them with each other, that is one that is working with one that is exactly the same but is not working and slowly running down the bad parts that way.  I found out that I SEE a lot more with a good multi meter (FLUKE) than with a cheap one.  I keep finding new parts that I want to see into what they do and think I can learn to use a scope on my own time with time.   What do you think?You can try to find somewhere "second hand" like Texronix TDS1002 (60mHz,2 channels,it can measure voltage,frequency and many other things),or even older.The price of such thing may be less than 400$. USB-oscilloscopes for PC without display has the same price,but they are not so suitable for everyday work.Of couse you can save a money,but will lose a time,just decide what's  more important for you.Actually nothing can replace oscilloscope-this is a vision,the higher in the antique top-list of senses[smile][Edited by - Krokhin on May 31, 2009 3:24:16 AM]