Oscilloscope and DMM Suggestions !

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Re: Oscilloscope and DMM Suggestions !

Postby JMPGuitars » Fri 08/10/18 9:30 am

geoff 1965 wrote:
Fri 08/10/18 8:41 am
cool guys!
regarding signal generators,what specs do you need for amp work? i.e. Khz, volts, waveform etc
I ordered the Tenma 72-505 for $34 which should be good enough for most basic stuff testing tube amps. Think of it this way: what wave form and frequencies does a guitar produce? You'd be looking for sine waves in mV, start at 150mV 1KHz.

I might buy a fancier generator for things like a Pulse function, which can be helpful for guitar amps. You can google the Hz for any note on a guitar if you needed to. Then you can pulse the frequency to simulate hitting the note if individual notes are causing issues.

I also setup a true isolated transformer and a GFCI outlet for safety.
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Re: Oscilloscope and DMM Suggestions !

Postby JMPGuitars » Fri 08/10/18 2:42 pm

I'm bored waiting for UPS to drop off my function generator, and a couple other fun things, and I found (of course) there's function generators, tone generators, spectrum analyzers, etc... all available as android apps. I tried out a couple of the function generators (the totally free one actually works really well). It has most of the functions we would need including bursts. The only limitations are the phone itself, and how you connect to it. I was using a poor quality old cable, so the waves were noisy (equally noisy on any app I tried on two phones).

EDIT: ...and for $2.49 there's one for Windows in the Microsoft Store. I tried it out and used it to test one of my amp heads. I actually ran my amp through an attenuator, and then used the line out (not speaker out) to run direct to the oscilloscope and it seemed to work fine for testing. I could see the distortion characteristics of the wave when cranked, etc...
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Re: Oscilloscope and DMM Suggestions !

Postby JMPGuitars » Mon 08/13/18 10:13 pm

I finally got the Tenma signal generator today. It produces very clean wave forms connected directly to the scope. I tried both sine and square (that's all it does) and swept across, and it worked very well. For $34 it's a great buy. I'll connect to the software signal generator if I ever need pulse function. It's really tempting to purchase a more expensive generator, but I can't think of any reason.

UPDATE: I've been going through an old amp build and cleaning things up and changing/updating parts of the circuit using the combination of the Tenma/Rigol. They're definitely great together.

I made it a little further in the Rigol manual, and there's a "Frequency Counter Measure" function where the scope will display the frequency on the specified channel. I ran the Tenma through my amp and the Rigol on the amp output (via the attenuator line out), and tested the frequencies on the Tenma, and it was accurate. The rest of the manual is so boring it was a welcome break. ;)
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Re: Oscilloscope and DMM Suggestions !

Postby JMPGuitars » Fri 08/17/18 10:03 am

jobewan wrote:
Tue 07/31/18 8:10 pm
Hey StudioCat - just saw this. For what it is worth, I bought the Rigol DS1054Z - maybe the most ubiquitous scope on earth. Ads everywhere. But after digging through the piles of hype, I found it was the best deal. They are basically giving away all of the upgrades that people were hacking. I guess they figured it was easier to simply give it away and make it a feature. So that gets you a 100 Mhz scope with 4 channels and 24 Gigs of RAM. It is a pretty well made scope - watch the Aussie guy at EEV Blog - he does a pretty thorough teardown of it.
Did you confirm that your upgrades included the 100 Mhz bandwidth? I got all the "official" upgrades, but that list doesn't include the 100 Mhz. I found this out talking to the VP of the company I bought it from. The bandwidth upgrade apparently isn't supported. I'm assuming this is because it would render a few of their products instantly obsolete (including more expensive scopes).

The hack still should work, and even though it potentially voids the warranty, supposedly they still stand behind the products. I have mixed feelings about this, but I also don't think I care since we're not really going anywhere near that...and we can always apply the hack in the future (outside of the warranty period) if we ever needed to.

Thanks,
Josh
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Re: Oscilloscope and DMM Suggestions !

Postby jobewan » Fri 08/17/18 12:15 pm

Hey Josh,

I was too impatient - I made the assumption that the upgrade codes would do the speed upgrade, so I ran the hack. Didnt want to wait for the vendor to get me the codes. They came a day later... The hack absolutely unlocked the 50 to 100 Mhz software upgrade. In fact, when I run the output of the scopes stats now it no longer calls the scope a DS1054Z. The model of the scope is now DS1104Z.

BTW - if you check out the Rigol site, all of the features that got unlocked by the hacks are now free and included with the base scope, including the 50 to 100 Mhz jump. I imagine you can get that if you go back to your vendor and complain about it not being included.
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Re: Oscilloscope and DMM Suggestions !

Postby JMPGuitars » Fri 08/17/18 1:40 pm

jobewan wrote:
Fri 08/17/18 12:15 pm
Hey Josh,

I was too impatient - I made the assumption that the upgrade codes would do the speed upgrade, so I ran the hack. Didnt want to wait for the vendor to get me the codes. They came a day later... The hack absolutely unlocked the 50 to 100 Mhz software upgrade. In fact, when I run the output of the scopes stats now it no longer calls the scope a DS1054Z. The model of the scope is now DS1104Z.

BTW - if you check out the Rigol site, all of the features that got unlocked by the hacks are now free and included with the base scope, including the 50 to 100 Mhz jump. I imagine you can get that if you go back to your vendor and complain about it not being included.
Part of the hack changes the model number (that part of the model number is the bandwidth). This is actually part of the issue with the warranty and the easiest way to tell it's been hacked. From what I've read, it can be reversed if you need service.

Do you have a link where it says the 100 Mhz is included? I haven't been able to find that? It is possible the guy was wrong even though he assured me he's an expert. ;)

Thanks,
Josh
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Re: Oscilloscope and DMM Suggestions !

Postby JMPGuitars » Tue 08/21/18 3:22 pm

For anybody considering oscilloscopes, it looks like the Siglent SDS1204X-E and SDS1104X-E are really good options also. The 1104X-E is preferred over the 1054Z by a few people at EEV blog. The FFT function on the Siglents is also supposed to be better than that Rigol model, but I dunno if any of us will really use that or not. YMMV right?

Another good option, if you don't mind connecting to a computer, is the "Analog Discovery 2 Pro Bundle." It's a 14-bit oscilloscope with a built in AWG for only $299 (bundle price). Supposedly the software for it is really good too. You need that bundle that comes with the probe connections. I don't know how great the probes are, but they're probably not bad.

Speaking of probes, I recently got a great deal on ebay for some Pico TA131 250Mhz probes that are great. I got them for $12 each shipped.
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Re: Oscilloscope and DMM Suggestions !

Postby JMPGuitars » Sat 09/01/18 5:25 pm

Wow. I was wondering why nobody was replying to this thread. I didn't realize the forum I moved the topic to was a hidden forum! Not anymore. It's back out, and looks like there might be some decent info hidden in here (almost 66K posts!).

Anyway. I returned the Rigol DS1054Z and bought the Siglent SDS1104X-E instead. So far, I definitely like it more. The Rigol is fine, and definitely good for the price, but the Siglent had some additional features and specs I wanted.

I will say, I'm trying to troubleshoot a parasitic oscillation, and the Siglent seems to pick it up better than the Rigol. Pretty interesting stuff. The Siglent in general is also a lot faster, so if you're impatient, it's a win. ;)
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Re: Oscilloscope and DMM Suggestions !

Postby JMPGuitars » Fri 09/14/18 9:04 pm

Okay, this was driving me nuts. I was troubleshooting an amp to get rid of a specific oscillation. Guess what? It wasn't in the amp. I only figured it out because I was still seeing the oscillation/waveform when I unplugged the amp power cord!

This is a screenshot of what a probe floating (not connected) next to an outlet in my house looked like:
SDS00027.png
After a bunch of plugging/unplugging of devices in my house I found out it was a power supply in a different room in my house causing that issue...in my entire house.

Once that device/power supply was disconnected, my AC looked like this:
SDS00036.png
If it weren't for the oscilloscope and dumb luck I would have never figured that out. I would have been chopsticking that amp forever with no luck. Ridiculous.
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Re: Oscilloscope and DMM Suggestions !

Postby Daviedawg » Sat 09/15/18 2:02 am

It's infuriating when something like that happens. But great you found it.

Dd
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Re: Oscilloscope and DMM Suggestions !

Postby JMPGuitars » Wed 09/19/18 9:34 am

Check out this cute adapter:
_JMP3402.jpg
_JMP3400.jpg
Pretty handy when measuring from a parallel output.
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