|SoulFetish||6/12/2017 5:57 PM|
|Look who's all grown up! Finally able to pull the trigger and get an oscilloscope|
I just found a great deal on a Rigol DS1102E 100MHz Digital scope and bought it. Should be here by Wednesday and I can't friggin' wait!
These have been really well reviewed by owners and at a price of $190 (lightly used) w/$10 shipping and a warranty, I thought it was a lot of value.
This is long overdue, and it just so happens that I really need one right now for a project.
I don't think it comes with any probes, so what should I be looking for in that regard?
|nosaj||6/12/2017 7:47 PM|
I bought 1x-10x 100mhz probes for my 20mhz scope. They've been just fine. Just make sure your probes voltage rating is good and know what the input voltage max on the scope is.
|g1||6/12/2017 8:25 PM|
|Enzo||6/12/2017 9:56 PM|
|Right now you just need to learn to use the scope, and for that matter when to stop scoping every darn thing in sight. I have used the basic cheap probes on the market for years, and they have worked fine for me. I am sure the $150 probes work well also, but $30-40 has worked in my case.|
We almost always use probes on X10 mode. I have bought probe sets with dedicated X1 and X10 probes, and wind up using the X10 most of the time. But the X1/X10 switch on the probe is useful. I run X10 mostly, but now and then I am searching a low level signal or maybe a noise signal, and X1 is useful for that. SO get yourself a probe with the switch.
I used to do more business with MCM, and bought probes there. I have a local electronics parts store, and I have bought them there.
|TimmyP1955||6/13/2017 6:04 PM|
|Put a piece of tape over the probe's 1x/10x switch, so you cannot accidentally switch it to 1x and blow the input of your scope.|
|nosaj||6/13/2017 6:11 PM|
|Randall||6/13/2017 7:45 PM|
|The Dude||6/13/2017 8:15 PM|
|What brand and model scope is it?|
|drewl||6/13/2017 8:33 PM|
I have at least three around here somewhere, and a ton of other test equipment.
Fortunately I used to work on test equipment back in the '80's.
Let me tell you about TUBE oscilloscopes!
Got a bunch of RCA 6550's that were in the Tektronnix scopes, as well as little spools of silver solder!
We used to joke that techs in the old days must have been huge hulking guys to lug around 80lb "portable" oscilloscopes.
Love them switchable x1/x10 probes.
We used to get free samples from a local mfgr.
|g1||6/13/2017 9:48 PM|
|Mick Bailey||6/14/2017 12:42 AM|
|What overload protection is on those scopes - would it need an additional input protection circuit? An accidental slip from scoping an AC grid signal on a 6L6 socket could give you maybe 460v on the input. Tube equipment has a much greater voltage range than probably any other gear you're likely to work on. For me, perhaps I'd be looking to build a little limiter/protection box if I were to move away from my Tektronix scope.|
|drewl||6/14/2017 3:01 PM|
|For our spectrum analyzers at work we made up probes with a cap on them to keep dc out.|
They can only handle a few volts dc.
You could use something similar for scoping high voltage, with like a 1kv cap.
|nsubulysses||6/14/2017 3:19 PM|
|scopes are fun. I have a bunch of 50s-80s tektronix scopes that are usually found on craigslist or ebay for free-$100.|
I have one new scope, Rigol DS1054Z . It is pretty inexpensive but cool and does A LOT. I use it as my reference for my old scopes to check their cal, and usually they are amazingly either in cal or not far off. I use the rigol as my main scope because it's fast and easy (lots of digital measurements on the screen rather than count the graticules and get out the calculator) and has 4 channels.
Those rigol probes have a real cheap-ass feel compared to the old tektronix ones but a good scope none the less, and maybe not a fair comparison at all anyway
RIGOL RP2200 Passive Oscilloscope Probe Kit (Qty 2) all Accessories, Brand New!
make em an offer they can't refuse
|Chuck H||6/15/2017 11:16 AM|
|Enzo||6/15/2017 12:07 PM|
|I see it over and over. Like when someone finally gets and ESR meter. All of a sudden they measure ESR on all the caps they see, and ESR becomes the most important thing since air to breath. With scopes, guys find that no matter what they are looking at, if they turn up the vertical far enough they eventually see some sort of noise waveform, or the local AM radio station, or SOMEthing. I made up the term "trace chasing" for the phenomenon. You chase after a trace long enough, you'll find one.|
|Chuck H||6/15/2017 6:06 PM|
I did have an odd thing happen once where micro scanning the waveform helped. Sometimes with tone stacks the HP cap will create a distortion artifact when there is a lot of LF being "blocked" (if that's even the right way to think of it?). I had an amp that would crackle just audibly on some clean tones and I traced it to the treble cap. Replacing the cap didn't help. So I took a good close look at the wave form and saw the artifact. I struggled for hours trying to mitigate it in one way or another before I opened up another amp and probed it for a reality check. It turns out that this is normal, but worse on some amps and more or less audible in different overall designs. In this case the artifact was greater than usual and the design really allowed it to be heard. It was a silver face Champ. I fixed it by reducing gain to the tone stack a little, bumping the gain in the following stage and I can't remember what all else. But it was the scope that helped me find it and the scope that allowed me to see it was "normal"-ish and it was the scope that allowed me to monitor progress in the circuit modifications. I did a lot of mods to that one and the owner calls it his little *umble
|TimmyP1955||6/15/2017 6:40 PM|
|SoulFetish||6/19/2017 12:46 PM|
If it beeps, bloops, blinks, or buzzes, it's getting scoped. I'm gonna scope like LT scopes. Hell, I'm gonna' Scope like The State of Tennessee vs. John Thomas for violating the Butler Act.... in 1925.
|SoulFetish||6/19/2017 1:51 PM|
|do you guys use active differential probes to measure high p-p voltages (ie. plate)? Or, passive 100x probes?|
|nickb||6/19/2017 4:13 PM|
|SoulFetish||6/19/2017 5:29 PM|
|Chuck H||6/19/2017 7:53 PM|
|I only have a 10x/1x switch probe. My scope has a max 400 input voltage. I haven't had a problem. I don't scope the power tube plates much though. Usually if I'm already out that far on the signal chain I'm scoping the output jack. |
What is the input voltage of your scope?
|SoulFetish||6/19/2017 10:15 PM|
|Chuck H||6/19/2017 10:25 PM|
And you almost certainly won't. It's a hard mistake to make when the CHASSIS IS RIGHT THERE!!! Unless you're measuring a swing voltage across two points. But that's usually pretty specific.
10X means you can have peaks to 4000V on your scope using a 10X probe. I think you'll be OK if you're paying attention. Though I admit that I've had a couple of close calls with "my" scope by NOT paying attention.
|Justin Thomas||6/19/2017 11:14 PM|
|Probes were cheap enough; I got a x1/x10 AND a x10. And I may be willing to make up whatever little safety gadgets I have to to spare my scope. When I get one! Eventually... I try not to look at these kinds of things as disposable, even if I <DO> get a great deal. That $10 multimeter is worth playing safe with; you'll be that much more conscientious later on with the good stuff. And who knows when the next great deal will come along? Besides, less spent on blown-up equipment = more spent on amp parts!|
|nickb||6/20/2017 1:12 AM|
My scope has a limit of 150V so it's really not the best solution for probing anywhere where you need AC coupling and where there is more than 150V DC. When the scope is switched to AC the DC input voltage appears across that cap. It's quite common to hear people use a capacitor on the end of the probe to look at AC signals in the presence of high DC and I do this often myself, but there is a short period of time when you first probe during which that scope input cap charges and nearly high DC voltage appears across the scope input cap. Keep the cap small say 1,000pF for a x10 10Mohm probe. The best solution is really an external attenuator with switchable AC coupling and a limiter to prevent scope damage - Juan has a posted a suitable design on these pages before.
|Enzo||6/20/2017 5:51 AM|
|ANyone really concerned could make a tiny voltage divider with a couple resistors and clip the probe to it, then use an additional probe to the circuit.|
|SoulFetish||6/20/2017 8:47 AM|
|Fahey (or anyone), if your out there, do you have alink to the probe topic that Nick was refering to?|
|Tom Phillips||6/20/2017 8:57 AM|
|http://music-electronics-forum.com/t31492/ and http://music-electronics-forum.com/t37999/ |
Still looking for the discussion that includes Juan's attenuator that will substitute for a good HV probe.
Edit: Juan's post is in the discussion at Test bench amp setup advice - Music Electronics Forum
|nickb||6/20/2017 10:55 AM|
Oh..., the 1pf is just a guess. It's there to maintain the HF response and can usually be left out. The actual value depends on the zeners and chosen to get a flat top on a square wave. Resistors do have a voltage limitation so a string of six is used to get to 3kV
|SoulFetish||6/20/2017 11:31 AM|
Should I include a capacitive divider for the attenuator? I guess you have the 10X probe function as well. May be overkill.
|nickb||6/20/2017 11:47 AM|
|SoulFetish||6/20/2017 12:29 PM|
Works with the reactance. Im sorry. The example was clear, my mind was not
|Chuck H||6/20/2017 11:24 PM|
|FWIW Enzo's capacitor in series with the scope' thing is great for monitoring PI AC circumstances. PI measurements are sometimes problematic because of the high input impedance. A series cap solves for this WRT AC measurements.|
|nickb||6/21/2017 12:37 AM|
|SoulFetish||6/24/2017 4:19 AM|
|Nick, should I use a short lenght of RG58 (or some other 50 ohm cable) to couple the attenuator to the scope?|
|nickb||6/24/2017 5:58 AM|
|SoulFetish||6/24/2017 6:28 AM|
|Yeah, the probe I have now isnt rated for the high voltage side of this circuit. Im going to need something suitable.|
|nickb||6/24/2017 6:41 AM|
Afterthought: Whatever you use keep it a short as possible. A foot of twisted HV pair might be good. The objectives are insulation and low capacitance. If you can build the megohm resistors right at the tip that would be ideal - just like a real probe. Then longer screened cable would be fine as it's capacitance appears across the output where the impedance is lower and that is a good thing. You seem to have excellent build & mechanical skills (jealous) so I'm sure you'll come up with something
|Tom Phillips||6/24/2017 8:48 AM|
|nickb||6/24/2017 10:57 AM|
|Tom Phillips||6/24/2017 11:04 AM|
|Chuck H||6/24/2017 1:09 PM|
|For a 3KV rating you'll need to put a bunch of resistors in series anyway. This almost calls for it's own housing. Something like a Bic pen case with a probe at the tip end then a shielded cable coming out of the other. Now the cable only needs to handle 300V for a 3KV input at the Bic probe tip. Then some way to couple that cable to the 1X probe.|
|SoulFetish||6/24/2017 2:01 PM|
|Tom Phillips||6/24/2017 2:33 PM|
|Tektronix Probe 2883619. P6007, BNC, 6, 100X~ 2.2pf. 10M? | eBay ) |
The P6007 is the model I posted about in the thread at http://music-electronics-forum.com/t31492/. It's design is such that it attenuates both the AC and the DC voltage. Therefore, the P6007 does not exhibit the problem that allows the capacitor inside the scope to charge to the full un-attenuated DC voltage being probed. The MEF thread I referenced already explains this and contains the Tek Probe circuit so I won't repeat the info here. The designs and performance of commercial 100X probes vary. One needs to check the specifications and read the operating manuals to determine if the probe will work for your application.
|nickb||6/25/2017 12:51 AM|
The answer is much the same but without the HV restriction and capacitance is less critical.
|SoulFetish||7/5/2017 8:31 PM|
Sometimes I have to remind myself that it just makes sense to spend the money and buy something, vs making it or finding a way around it.
I don't know what the hell my problem is; I spent over an hour and a half researching solvent dyes for polyvinyl chloride because I have a surplus of white 18AWG UL1015 wire and didn't want to buy more to have different colors. Actually, I do no what my problem is. I'm the perfect storm of cheap, broke, and hubristic. I finally snapped out of it and said to myself "Dude, just pay the $6 a piece for a couple of 25' rolls and pull your head out of your ass".
|Chuck H||7/5/2017 8:55 PM|
|FWIW I spend the extra buck a roll on "irradiated" PVC now. It's far tougher and shrinks about 20% of what standard PVC does under the iron. So worth it. It's certainly cheap enough and the results after soldering and construction are better. Heads up though... DO check for voltage rating on the jacket. When you start looking at irradiated PVC you get into the realm of real pro's that know how to spec. So none of the dunderhead work is done for you. The rating on the material might be strictly AC. I had this problem once and had to shotgun change an order to get lead wire appropriate for the DC voltages we use. The vendor got a little grumpy about it and I had to point out that they hadn't specified AC or DC on the voltage rating!!! Sorry I can't remember where I bought it. It was a few years ago and I've barely cracked into the 600 yard rolls But irradiated IS what you want. Offered for our consideration. And irradiated PVC highly recommended by this guy.|
|Justin Thomas||7/5/2017 9:42 PM|
|I remember my first roll of Teflon wire from Belden. I panicked when I saw the 300V rating AFTER I had punched out the center label and couldn't read it entirely. I called the store I bought it at and they said, "that's when you are using it submerged in gasoline; it's 600V." Huh, never woulda thunk it...|
Wow, what a relief... I think.
|Chuck H||7/5/2017 10:13 PM|
|Yeah.?. All kinds of oddness WRT voltage ratings. Why in the hell would they expect anyone to read a spec. and just KNOW "when submerged in gasoline"??? That's just the sort of thing that comes up when you order wire IME. You do learn what to look for, but that doesn't mean it's always represented in completed statements Like we all have extra dough for finding out what we ordered isn't quite right!?! Lazy product descriptions bother the $h!t out of me.|
|SoulFetish||7/5/2017 10:14 PM|
|The Dude||7/5/2017 10:20 PM|
|SoulFetish||7/5/2017 10:27 PM|
|SoulFetish||7/5/2017 10:38 PM|
|on a side note, you guys ever read something wrong the first time and whenever you see it again after that you keep pronouncing it wrong in you head even though you know better? |
The first time I came across the term "irradiated PVC" wire, I read it "irradated". Like, irradating was a mysterious new technique for processing PVC used by manufacturers.