oscilloscope probes

[aliasdck]

I have some cheap (~$20) generic 100Mhz oscilloscope probes. I am currently looking for a used 200Mhz scope but Im wondering what type of probes I should consider getting for it. The probes I've found so far are all very expensive (over $100 each). Anyone have any recommendations on which probes I should get? I'd rather not spend too much money if I don't have too.

I plan to use the oscilloscope to help me diagnose problems in plasma tv's... service manual recommends 200Mhz scope.

[cadiman]

I have a hitachi 100mhz and use the probes that came with it. When you pick up a scope it will normally have probes with it. You will need to calabrate them. I have been using mine on plasmas and I have been able to dial in and set waveforms by the book.
I have not used my scope for diag on a tv yet. I only used it for set-up and set-down on the y sus boards.
I have a scope for automotive use that is pc based with lots of waveform storage and good for record keeping, but has voltage limits (I use an inductive pick up or transducer (picks up vibration). Something to look into. Wizard would know more. I have never read very high waveform frequencies on my scope,(on plasma) but I am new to plasmas.
I have mostly used scopes to look for signals to trace through a board then looked at the waveform for distortion. You have a good question here and I look forward to all the answers! Thanks, Cadiman

[aliasdck]

Currently I need a scope capable of looking at setup and setdn waveforms as you mentioned. I'm glad to hear 100Mhz is plenty for this application though ill likely still try to find a 200mhz.

I've been searching ebay for used scopes. Most of what I've come across in my price range do not include probes. I'm thinking about getting a tektronix 475 but haven't made up my mind yet.

[cadiman]

I do agree I wish I had the 200, but I mostly do audio work and automotive as well. I purchased my hitachi new for around 2000 bucks and didn`t even price out the 200.
They should be cheap now and I am not sure 100mhz is plenty I haven`t worked on every unit out there. I know you don`t measure 100psi with a 100psi guage you use a 200psi guage. I am sure the same goes for a waveform. I know by setting the timebase I have plenty of chase speed to catch a plasma signal....for now


I would try to find something local. Only use ebay for a price guide. I wouldn`t want to ship somthing like that.

Cadiman

[intp1000]

IMHO 200MHz is enough, maybe even a little more than enough.
When I worked for the military industrial complex we had a rule of thumb that any test equipment we built; I was an electrical design engineer, had to have 10X the resolution of the measurment tolerance. So, 200MHz may be about 10X the requirement. Now, in normal shops equipment which is 3 to 5X the requirement is OK. You're not trying to characterize circuits, just looking for a close match. Therefore, while 100 MHz probes may distort the waveform a little trying to buy 500MHz probes (you are going to use them on a 200MHz scope ) may be overkill. I've bought 500MHz probes on epay for 48 $US. Just have to wait and not be anxious about a time frame. While a 100MHz BW probe is not the best match for a 200 MHz BW scope they will work with up to 30 MHz with only small degregration in waveform display (unless you're looking a 1ns rise time square waves). But then, you're not so don't worry. Just use them knowing that sometimes really fast rise time measurement won't quite make it.
Have fun.

[aliasdck]

Thank you for your advice.

I just acquired a tektronix 475 a couple of days ago. I'm not going to bother trying to find better probes as it sounds like my current probes will be sufficient.

Let the testing begin...