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Starter Oscilloscope for amp building & repair

Tony Bones

Member
Messages
1,214
The delay with digital scopes is sometimes due to their having a large buffer that needs to get filled before the display is updated. On newer scopes (or older really expensive ones) this buffer holds more than a screen full of data. I have a cheap Rigol with 24Mpts of buffer. (!!) Depending on how it's setup it might take several seconds to fill the buffer. But the screen is only 800 points wide, so only the first 0.03% of the buffer gets displayed. It's great for capturing really long waveforms and then analyzing them later, but it seems like the scope locks up for a while. On the other hand, by adjusting the sample rate and reducing the buffer length I can get it to refresh in almost real time. Or, it has a fast mode, which is virtually as fast to refresh as an analog scope.

I don't know how long the buffer is in the Hantek, but it's sure to be much more than one screen full. Look for an option to limit the size; make it as small as it will go for speed, and increase the sample rate. If, some day, you want to record a long signal you can always readjust it for that application.

Read the manual! :p
 

AudioHacker

Member
Messages
254
Keep us posted, I'm in the market myself and the price is right on the one you purchased.
Just posted
The delay with digital scopes is sometimes due to their having a large buffer that needs to get filled before the display is updated. On newer scopes (or older really expensive ones) this buffer holds more than a screen full of data. I have a cheap Rigol with 24Mpts of buffer. (!!) Depending on how it's setup it might take several seconds to fill the buffer. But the screen is only 800 points wide, so only the first 0.03% of the buffer gets displayed. It's great for capturing really long waveforms and then analyzing them later, but it seems like the scope locks up for a while. On the other hand, by adjusting the sample rate and reducing the buffer length I can get it to refresh in almost real time. Or, it has a fast mode, which is virtually as fast to refresh as an analog scope.

I don't know how long the buffer is in the Hantek, but it's sure to be much more than one screen full. Look for an option to limit the size; make it as small as it will go for speed, and increase the sample rate. If, some day, you want to record a long signal you can always readjust it for that application.

Read the manual! :p
Cool, that makes sense. I’ll try adjusting the settings some and see if it gets “quicker”. I’m still getting familiar with all of the options on this scope (and scopes in general), so I expect some learning curve :)
 

xtian

Gold Supporting Member
Messages
2,322
If you think about how much harder it is for the scope to render a guitar signal than a constant 1KHz signal generator, this makes sense. The guitar signal has many more peaks, valleys, & variations than the constant signal. The harder the scope is working, the slower the display is. I’m not sure if this is due to lack of CPU power, GPU power, slow ADC, or a combination of all three.
I don't agree that this is the case, at least with my DSO5072P. I see the same lag in displaying waveforms, whether they're simple or complex. As a simple test, just observe a sine wave, and disconnect the probe from the signal, reconnect, disconnect...all while watching the scope. It takes some fraction of a second for the wave to appear on and disappear from the screen.
 

AudioHacker

Member
Messages
254
I don't agree that this is the case, at least with my DSO5072P. I see the same lag in displaying waveforms, whether they're simple or complex. As a simple test, just observe a sine wave, and disconnect the probe from the signal, reconnect, disconnect...all while watching the scope. It takes some fraction of a second for the wave to appear on and disappear from the screen.
I was referring more to when it “chokes” in the middle of the waveform (not disconnecting/reconnecting the source). I think “Tony Bones” is on the money with his “buffer” explanation. His post was in this same thread.
 

Heavymetal66

Member
Messages
17
I was referring more to when it “chokes” in the middle of the waveform (not disconnecting/reconnecting the source). I think “Tony Bones” is on the money with his “buffer” explanation. His post was in this same thread.
I know this is an older thread and apologies for the necro-post, but I’m looking to get this exact scope (DSO 5102P) and I’m wondering how you like it after using it for a while now? Unfortunately there isn’t a lot of information out there regarding DSO’s for amp repair.

I’m just getting into amp repair as a hobby so it’s not like I’ll be using this on a daily basis. A lot of people still seem to recommend older CRT scopes but I prefer the smaller size of DSO’s as I have limited bench space. Thanks.
 

xtian

Gold Supporting Member
Messages
2,322
The probes are the standard, inexpensive stuff you can get on eBay, and seem fine to me. Switchable 1x/10x, removable tip spring clip, removable ground clip, adjustable capacitance trim pot, rated 600v. No complaints.
 

JPH118

Member
Messages
2,763
How do you, @Tony Bones, @eolon, @Kyle B, @JPH118 feel about the probes included with the Hantek? Should a buyer look to spring for better probes, and if so which ones should we look at?
Literally just using mine a moment ago... they’re fine, I use an extra clip for ground, since the one on the probe is so short, but that’s not really a problem. Several years now and they’ve worked fine.

FYI, I have the Siglent, not the Hantek... basically the same, but the Auto function on the Siglent was worth it for me. Saves a lot of futzing around for quick readings (futz is a technical term here).
 
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tonsound

Member
Messages
75
Siglent SDS1102CML, has th same functions as hantec but also a usefull auto trigger button. Application for fft is to slow, but test with a 1khz sin wave to amp, output measured at 8 ohm resistor is fine. see here (here the rigol in comparison, but same quality as siglent)
 
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Heavymetal66

Member
Messages
17
The probes are the standard, inexpensive stuff you can get on eBay, and seem fine to me. Switchable 1x/10x, removable tip spring clip, removable ground clip, adjustable capacitance trim pot, rated 600v. No complaints.
What is the actual input voltage on this scope as I’m not clear looking at the specs. If it’s 300v at 10x, does that mean it has a max input of 30v at 1x? Do I then need a 100x probe if I’m going to signal trace at the plates or screen grid? BTW, I’m looking at the DSO4102C which from what I understand is the same as the 5102P, but includes a waveform generator. Same specs as below:

CAT I and CAT II: 300VRMS (10×), Installation Category;
CAT III: 150VRMS (1×);
Installation Category II: derate at 20dB/decade above 100kHz to 13V peak AC at 3MHz* and above. For non-sinusoidal waveforms, peak value must be less than 450V. Excursion above 300V should be of less than 100ms duration. RMS signal level including all DC components removed through AC coupling must be limited to 300V. If these values are exceeded, damage to the oscilloscope may occur.
 

HotBluePlates

Member
Messages
9,891
What is the actual input voltage on this scope as I’m not clear looking at the specs. If it’s 300v at 10x, does that mean it has a max input of 30v at 1x? ...
Right. But you'll need to think about the difference between RMS, Peak and Average voltages.

1603050400443.jpeg
300v RMS * √2 = 424 volts peak. So don't try to measure more than ~420v d.c., or any combination of d.c. + a.c. voltage that puts more than 420v between the probe's common & tip. There may be an A.C. Coupling Mode on this scope (or not), which would block the d.c. voltage and measure only the a.c. voltage (which will be less than 400v everywhere except output tube plates).

There are high voltage probes available that divide-down the voltage. But they'll cost you ($120-500 each is the typical range, which more expensive probes for some special uses). $113 for a 2kv 100:1 probe, and $333 for a 10kv 1000:1 probe.
 

Heavymetal66

Member
Messages
17
Right. But you'll need to think about the difference between RMS, Peak and Average voltages.

300v RMS * √2 = 424 volts peak. So don't try to measure more than ~420v d.c., or any combination of d.c. + a.c. voltage that puts more than 420v between the probe's common & tip. There may be an A.C. Coupling Mode on this scope (or not), which would block the d.c. voltage and measure only the a.c. voltage (which will be less than 400v everywhere except output tube plates).

There are high voltage probes available that divide-down the voltage. But they'll cost you ($120-500 each is the typical range, which more expensive probes for some special uses). $113 for a 2kv 100:1 probe, and $333 for a 10kv 1000:1 probe.
Thank you for the explanation. This scope has AC coupling per the spec sheet:

Inputs CouplingAC, DC, GND

So if I’m running in AC coupling mode and using the 10x/600v probe, I could safely signal trace a 1KHz signal at the plate on my amp (plates are running at 398 vdc)?

I haven’t used an oscilloscope since college which was about 30 years ago, so I clearly have some reading to do. But I appreciate your help as I wanted to better understand this before I bought the scope.
 

HotBluePlates

Member
Messages
9,891
CAT I and CAT II: 300VRMS (10×), Installation Category;
CAT III: 150VRMS (1×)
... Excursion above 300V should be of less than 100ms duration. ...
So if I’m running in AC coupling mode and using the 10x/600v probe, I could safely signal trace a 1KHz signal at the plate on my amp (plates are running at 398 vdc)?
I read the specs in your initial post to mean when using a 10x probe the voltage can be as high as 300v (and 300v - 420v can only be for <100msec, which equates to ≥10Hz).

So no low-frequency or d.c. above 300v, and even then only with the 10x probe.

What does that mean? You can probably check a.c. output voltage of preamp tube plates and maybe the phase inverter, but don't poke an output tube plate. Or else, spring the few-hundred-$$$ extra to by a higher-voltage 100x or 1000x probe.

So the 10x probe can handle 600v, but the scope input cannot handle 600v/10 = 60v (only 30v RMS or ~42-45v peak).



If you hadn't noticed, safe use of test gear means you should have some idea of what to expect in a circuit, before you go poking it.
 

Heavymetal66

Member
Messages
17
I read the specs in your initial post to mean when using a 10x probe the voltage can be as high as 300v (and 300v - 420v can only be for <100msec, which equates to ≥10Hz).

So no low-frequency or d.c. above 300v, and even then only with the 10x probe.

What does that mean? You can probably check a.c. output voltage of preamp tube plates and maybe the phase inverter, but don't poke an output tube plate. Or else, spring the few-hundred-$$$ extra to by a higher-voltage 100x or 1000x probe.

So the 10x probe can handle 600v, but the scope input cannot handle 600v/10 = 60v (only 30v RMS or ~42-45v peak).



If you hadn't noticed, safe use of test gear means you should have some idea of what to expect in a circuit, before you go poking it.
Correct, I understand the voltage rating on the probe is separate from the scope, and the max I can probe with the scope is 300v RMS - not that I would go that high. I briefly confused the measure of my DMM and after reading your reply remembered the DMM is an RMS voltage. It’s making sense now.

I’ll be reading up on his stuff before I start using the scope. Thanks again.
 




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