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Need oscilloscope advice
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Jeremy112




Joined: 28 Sep 2006
Posts: 2645
Location: Fond du Lac, WI


PostLink    Posted: Thu Oct 12, 2017 6:33 pm    Post subject: Need oscilloscope advice Reply with quote


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Wondering what bandwidth I would need out of an oscilloscope for video, and audio usage. What's ideal bandwidth for both? I have never owned a scope, so I have no idea what I should be looking for.

I need one mainly for audio, but I want it capable of being used for video as well.

Help me out test instrument guru's Smile

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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24296
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Thu Oct 12, 2017 6:40 pm    Post subject: Reply with quote

Depends on what you want to do. For servicing, I've been using my trusty Leader 35Mhz scope that I bought back in 1985 or so. Since audio has a frequency response of 20Khz, you'll be fine. For video troubleshooting, you really don't need anything else.

Now, if you're doing mods, and need to check video frequency response, then a 200Mhz scope is what you need.

I have a couple of spare scopes, one I think it s 30Mhz, the other a 40. I don't have probes for them, but I'd sell the scope(s) for under typical ebay pricing, and probes are cheap on eBay.
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cmjohnson




Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Thu Oct 12, 2017 8:29 pm    Post subject: Reply with quote

Ah, one of my fields in which I have some experience!

If the question is oscilloscopes, the best answer is "Tektronix".

I am not alone in considering the 24xx series scopes, which have digital controls but analog signal paths,
to be the finest scopes ever made. If you can get a good one that has been gone through, recapped, rebuilt, and refurbished,
there is not a finer scope to be had anywhere and they STILL go for less than many brand new digital scopes that aren't anywhere
near as good.

But they really need to be rebuilt scopes as the capacitors in the power supplies, if original, are dead of old age.

You may opt instead for a newer digital oscilloscope, and in that case because of performance limitations I would not recommend
buying a model that is more than 10 years old. Early DSOs just weren't that great for use on dynamic analog signals unless they
were hideously expensive when they were new.

Let's regroup and as the important question: What's your budget? I'll be glad to make recommendations for specific models within your budget.

Don't be afraid to invest in GOOD probes. A mediocre scope with good probes is better than a great scope with cheap probes.
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gjaky




Joined: 05 Jun 2010
Posts: 2789
Location: Budapest, Hungary


PostLink    Posted: Thu Oct 12, 2017 8:46 pm    Post subject: Reply with quote

Yeah, for audio use in fact you can't find an oscilloscope these days which is "too slow", but there is a difference in Volts sensitivity, some scope have 10mV/div sensitivity while others may have 5mV/div or even 2mV/div, if you are into RIAA correctors and such, then a 2mV/div oscilloscope may be handy.

For video: A Motorola application note dealing with high speed CRT amplifiers suggested to use 300MHz oscilloscope at least when measuring a 100MHz bandwidth circuit, but here circuit probing is also very critical as simple 10:1 probes (no matter what bandwidth is writen on ot) may cause too much load on RF circuits (because their DC resistance may be 10MOhms but their dynamic impedance is dominated by the probe's input capacitance that is in the range of 10-20pF, now 10pF at 100MHz appears to be 159 Ohm "resistance"). Otherwise probing at low impedance (50 Ohm) or using a special high-impedance FET probe, so if you are serious you should consider these to the budget as well.

The Tektronix 2465 (and its variants) is considered to be the best all-around analogue oscilloscope, and even the base model (the 2465) can meet all above mentioned parameters.

With digital oscilloscopes you can get a lot of fancy features like automatic measurements, waveform capturing etc, but the high bandwidth there can be pricy, in any case don't look at digital scopes those have lower than 500Ms/s sampling (or not even indicated).

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projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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jbltecnicspro




Joined: 23 Apr 2016
Posts: 512



PostLink    Posted: Thu Oct 12, 2017 10:32 pm    Post subject: Reply with quote

Curt Palme wrote:
Depends on what you want to do. For servicing, I've been using my trusty Leader 35Mhz scope that I bought back in 1985 or so. Since audio has a frequency response of 20Khz, you'll be fine. For video troubleshooting, you really don't need anything else.

Now, if you're doing mods, and need to check video frequency response, then a 200Mhz scope is what you need.

I have a couple of spare scopes, one I think it s 30Mhz, the other a 40. I don't have probes for them, but I'd sell the scope(s) for under typical ebay pricing, and probes are cheap on eBay.


Not to hijack the thread (really - I'm not trying to!) but if I have a CRT monitor that has some overshooting, would your standard 35Mhz Leader be able to detect it? I'm not talking about video mods but just troubleshooting some visual distortion.
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
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Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Fri Oct 13, 2017 12:28 am    Post subject: Reply with quote

Sure, most likely a bad cap. Post a screen shot. I'll diagnose without a scope. Smile
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jbltecnicspro




Joined: 23 Apr 2016
Posts: 512



PostLink    Posted: Fri Oct 13, 2017 1:30 am    Post subject: Reply with quote

Ha thanks - I'll try and get one. It's intermittent, which is why it drives me nuts. Here one minute, gone the next.
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gjaky




Joined: 05 Jun 2010
Posts: 2789
Location: Budapest, Hungary


PostLink    Posted: Fri Oct 13, 2017 5:39 am    Post subject: Reply with quote

jbltecnicspro wrote:
Ha thanks - I'll try and get one. It's intermittent, which is why it drives me nuts. Here one minute, gone the next.

Then it will be a bad solder joint, you'd need a magnifier glass instead of an oscilloscope Razz

_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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jbltecnicspro




Joined: 23 Apr 2016
Posts: 512



PostLink    Posted: Fri Oct 13, 2017 11:42 pm    Post subject: Reply with quote

Thanks for the responses guys. Jeremy - sorry! Wasn't trying to hijack! Smile Looks like you got your answer though.
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24296
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Sun Oct 15, 2017 2:26 am    Post subject: Reply with quote

The scope I have is actually a 60Mhz, a Hitachi, and in good shape. This one (not my ad)

http://www.ebay.com/itm/Hitachi-60MHz-Oscilloscope-V-650F-/182826534331?epid=1103534342&hash=item2a914f85bb:g:ZR8AAOSwFzRZ4Agp

$50 USD plus shipping from 98230
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jbltecnicspro




Joined: 23 Apr 2016
Posts: 512



PostLink    Posted: Tue Oct 17, 2017 1:50 am    Post subject: Reply with quote

Here's a closeup of a solder joint for a capacitor:

https://imgur.com/a/KWSfy

Is this a cracked solder joint? There are quite a few joints on the board that are like this. Would this be causing my problem?
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24296
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Tue Oct 17, 2017 3:05 am    Post subject: Reply with quote

Most likely not.
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cmjohnson




Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Tue Oct 17, 2017 3:46 am    Post subject: Reply with quote

No, that's just solder that has shrunk as it cools. It often leaves a mark like that.

A ring crack is just that, a ring-shaped crack and it'll appear black inside the crack.
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jbltecnicspro




Joined: 23 Apr 2016
Posts: 512



PostLink    Posted: Tue Oct 17, 2017 11:16 am    Post subject: Reply with quote

Okay - thanks guys. I guess what I can do is just put it back together and see if I can grab a screenshot of it acting up. Another thing I just thought about - it has ferrite cores around the cable that goes from the video board to the neck board. Wondering if that may have something to do with it.

Curt you said it's likely a bad capacitor. Should I just look around to see if there are any telltale signs of one? Or would it be better to put the monitor back together and try to capture the signal ringing I'm seeing?
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gjaky




Joined: 05 Jun 2010
Posts: 2789
Location: Budapest, Hungary


PostLink    Posted: Tue Oct 17, 2017 11:33 am    Post subject: Reply with quote

jbltecnicspro wrote:
Okay - thanks guys. I guess what I can do is just put it back together and see if I can grab a screenshot of it acting up. Another thing I just thought about - it has ferrite cores around the cable that goes from the video board to the neck board. Wondering if that may have something to do with it.

Curt you said it's likely a bad capacitor. Should I just look around to see if there are any telltale signs of one? Or would it be better to put the monitor back together and try to capture the signal ringing I'm seeing?


BTW what is the model number of that monitor?

_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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Curt Palme
CRT Tech



Joined: 08 Mar 2006
Posts: 24296
Location: Langley, BC

TV/Projector: All of them!


PostLink    Posted: Tue Oct 17, 2017 1:47 pm    Post subject: Reply with quote

Give us a screen shot. No sense in shotgunning capacitors if they don't need replacing.
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Jeremy112




Joined: 28 Sep 2006
Posts: 2645
Location: Fond du Lac, WI


PostLink    Posted: Tue Oct 17, 2017 4:47 pm    Post subject: Reply with quote

Awesome, I knew I picked the right place to ask this question! Cool

I also want portability, I don't work in one spot like a typical bench setup, so portability would help. I've been eyeing up the Fluke Scopemeter 199B (or 199C possibly). This meter seems to meet the criteria you guys have mentioned here for the most part.

Would this be a good digital scope though? I'm not looking for 10000% precision, but something fairly accurate would be nice.

This is for the 199c, main (only) difference between the B and C is black & white LCD vs color LCD. http://www.fluke.com/fluke/r0en/solutions/portable-oscilloscopes/fluke-199c-color-scopemeter

I wouldn't be buying it new, it would be used, but I've been eyeing this thing up for some time now, hence why I figured you geniuses would be great people to ask Mr. Green

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gjaky




Joined: 05 Jun 2010
Posts: 2789
Location: Budapest, Hungary


PostLink    Posted: Tue Oct 17, 2017 7:02 pm    Post subject: Reply with quote

if digital, go with the colour LCD!
They are OK scopes, but I prefer "normal" scopes Smile You can consider any modern digital scopes as very portable, with scopemeter you get the battery operation and harsh environment robustness built in the price.

_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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jbltecnicspro




Joined: 23 Apr 2016
Posts: 512



PostLink    Posted: Tue Oct 17, 2017 10:09 pm    Post subject: Reply with quote

Curt Palme wrote:
Give us a screen shot. No sense in shotgunning capacitors if they don't need replacing.


Okay, hopefully I can produce it tonight.

gjaky - it's a GDM-F520. Sony's tightest production monitor at 0.22mm pitch. Common wisdom on the internet suggests the signal ringing is endemic to the model.


Last edited by jbltecnicspro on Wed Oct 18, 2017 8:53 pm; edited 2 times in total
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AnalogRocks
Forum Moderator



Joined: 08 Mar 2006
Posts: 26690
Location: Toronto, Ontario, Canada

TV/Projector: Sony 1252Q, AMPRO 4000G


PostLink    Posted: Wed Oct 18, 2017 4:10 am    Post subject: Reply with quote

jbltecnicspro wrote:
Curt Palme wrote:
Give us a screen shot. No sense in shotgunning capacitors if they don't need replacing.


Okay, hopefully I can produce it tonight.

gjaky - it's a GDM-F520. Sony's tightest production monitor at 0.22mm pitch. Common wisdom on the internet suggests the signal ringing is endemic to the model.


I have 4 of these, I seem to remember some ringing on mine too.

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