SH CRO vs DSO (again)

[Ian.M]

A 465B in good working order is a pretty nice analog scope.   2 channels + Ext trig view (for which you *WILL* need either an external attenuator or a switchable x1/x10 probe).  As I said earlier, that's good enough if you get into digital stuff, e.g Arduinos and slower MCUs.  For valve gear, its all down to how good your probes are.   Cheap and nasty probes may not have a suitable voltage rating for working on high powered stuff.  Also, its max input range is 50V/div , which, with 8 divs vertically is +/-200V, so if you are monitoring an output valve plate and you accidentally switch to x1, its probably game over.
 
I would suggest a new pair of budget x1/x10 switchible probes, and a used named brand fixed x10 probe with a higher voltage rating.  Up to 600V, fixed probes are fairly easy to find.  1000V probes are more expensive and *much* rarer - you'll probably pay as much as you did for the scope for such a probe new.  For a class B valve output stage you need a probe with a voltage rating of 2.5 times the HT voltage to allow for the CT primary to swing above the HT rail by as far as its other end is being driven down + an adequate safety margin.

[OriginalMuscian]

Ian:

If I understand you post, then a 600v probe will safely handle a HT voltage of about 240v. To go higher, I would need a 1000v probe.

I found some fixed x10 Hameg probes that are listed as:

Maximum AC Input Voltage: 40 V RMS
Working Voltage: 600 VDC including AC

The max AC Input Voltage rating is confusing to me. What does it mean?

Thanks!

[Ian.M]

Hmm....  Its confusing me too!   Got a link and a specific probe model number?

[dom0]

They just don't give the maximum AC at 50 Hz or so but at a few MHz, or even rated frequency. All passive probes derate maximum level by frequency. No exceptions.

[OriginalMuscian]

I ended up buying two cheap 1x/10x probes and a 100x. The Hameg probes were interesting but confusing. Here's the link to the auction:

http://www.ebay.com/itm/Two-100MHz-X10-Oscilloscope-Probes-/151913803442?hash=item235ec4aeb2:g:rh8AAOSwYHxWJDj~

[Ian.M]

The issue for those Hameg x10 probes the auction identified as "ETS1011" is:
What frequency do you have to start derating them above, and what's the derating curve?

Googling that part number, with x10 probe only finds that auction.   Without a datasheet,.I certainly wouldn't trust them above a couple of hundred volts so you probably did well to avoid them.

[janoc]

As I said earlier, that's good enough if you get into digital stuff, e.g Arduinos and slower MCUs. 

For that the new Rigol would have been a lot better - single shot capture, built-in serial decoding and 4 channel logic analyzer are a huge boon compared to counting and decoding bits manually on an ancient analog scope.

Nothing against the Tek, but unless it was less than $100-$150 delivered, it is not a good value today.

[Ian.M]

Yes. Using a 100MHz 2 channel analog scope with trigger view and delay timebase for digital work is a 'hair shirt' experience, but good for the soul.  If you only have a 50MHz  scope with a plain timebase and no trigger view, its like combining an augury with ritual self-flagellation.

[MrSlack]

I used a broken Philips PM3217 and home made probes that cost me nothing that the triggering was knackered on for about 10 years. Finally gave up in 2009. You can still get a lot of mileage out of junk, especially if it has a delay function

[tggzzz]

Yes. Using a 100MHz 2 channel analog scope with trigger view and delay timebase for digital work is a 'hair shirt' experience, but good for the soul.  If you only have a 50MHz  scope with a plain timebase and no trigger view, its like combining an augury with ritual self-flagellation.

Depends on what you are doing.

If you are troubleshooting signal integrity then 100MHz (preferably higher) is mandatory, and if the signal is repetitive then you probably don't need a storage function.

If you are troubleshooting mechatronics type signals and the signal can be made repetitive, then 20MHz is probably sufficient.

If you want protocol decodes at any speeds, then use a logic analyser or printf at either or both ends Get the signal integrity right, then don't use a separate tool that might interprets analogue signal differently to the real receiver.

[OriginalMuscian]

Nothing against the Tek, but unless it was less than $100-$150 delivered, it is not a good value today.

It was $157 delivered (no probes included) and is purported to work well. I will be using it (infrequently) to fix and maintain audio tube gear. My guitar amps are older than the scope, so there's some weird nostalgic value going on here for me. If I manage to come to my senses a few years from now, I'll donate the museum piece and get a DSO.

On another note, having shopped on eBay recently, the number of broken "Buy it Now" scopes listed > $150 shipped is seriously appalling.

[OriginalMuscian]

I received the scope today via UPS. US mail tracking shows both sets of probes were delivered on Saturday. However, I didn't get the probes. Either the busy mailman put them in the wrong box, or I was hit by Christmas-time rural mailbox thieves. I suspect the latter, so I ordered new probes and will keep a closer eye on my mailbox this time around.

The scope was packed surrounded by newspaper. For an item this heavy and fragile, I personally would only use large bubble wrap. Sure enough, I removed the scope from the box and found one of the rear feet had been broken off during shipment and was laying in the bottom of the box. 

I plugged the scope in and turned it on, and a horrible noise emanated from the fan area. It sounded like either the fan was rubbing or the bearings were going out. Fortunately, it turned out to be the fan rubbing on the grill (probably from the rough trip across the US). So I fixed it and then hooked wires between the BNC connectors and a signal generator in order to test the function of the scope. Nearest I can tell, all buttons, knobs, sweeps, lights, switches, delays, etc. appear to be working fine, and the scope is in very nice condition.

The only thing that appears odd or off about the scope is the test loop on the front of the scope only measures 157mv (it's rated at 300mv) with my Fluke DVM (verified with my cheap DVM). I notice my HP scope also measures a low calibration output voltage. Is this common with older scopes. Is it a sign that the scope is out of calibration?

Thanks for your input!

[alsetalokin4017]

The probe calibrator will put out a square wave, and the voltage spec for it is the peak voltage. DMMs do an excellent job of _averaging_ the voltage of square wave signals, as your testing seems to demonstrate.

Congratulations on your new-old scope!

[Brumby]

The only thing that appears odd or off about the scope is the test loop on the front of the scope only measures 157mv (it's rated at 300mv) with my Fluke DVM (verified with my cheap DVM).

Put the signal onto one of the inputs of your scope and you should see a 300mV peak to peak square wave.


Edit: Snap!

[tautech]

The only thing that appears odd or off about the scope is the test loop on the front of the scope only measures 157mv (it's rated at 300mv) with my Fluke DVM (verified with my cheap DVM). I notice my HP scope also measures a low calibration output voltage. Is this common with older scopes. Is it a sign that the scope is out of calibration?

No.

Many old scopes the Cal output is adjustable, check the SM.
Feed the Cal output into your HP to check it's REAL characteristics meet spec.

[OriginalMuscian]

I measured the peak to peak voltage, and it came out to exactly 300mv. So I hooked up a signal from an old HP 200CD Audio Signal Generator, and the scope sign wave closely matches the amplitude on the 200CD dial.



This scope is really super fun. I've already managed to fix a problem with a 1972 Fender Twin Reverb guitar amplifier that's been sitting in the corner for three years. Next, I'm going to measure the output of my 5500W generator in order to determine if the wave shape suits running household electronic equipment during a power outage.

OK, I know I'm grasping at straws here compared to you guys, but none-the-less, I'm really excited to have the scope.

Thanks for all of your help!

[Brumby]

Having an oscilloscope is really exciting.  You can SEE things that you never knew were there.

I remember when I picked up my first (and only) oscilloscope - a brand new Hitachi V-152B - from Dick Smith.  A big day indeed.

[tggzzz]

Next, I'm going to measure the output of my 5500W generator in order to determine if the wave shape suits running household electronic equipment during a power outage.

Unless you know what you are doing, you stand a good chance of destroying the scope, the scope probes, or yourself.

You would be wise to read, learn and inwardly digest the safety references in the "Praxis" subsection of https://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

[Ian.M]

+1.  I wouldn't even attempt that without a CAT III differential probe rated 600V RMS or better.   It would be possible with a x100 probe with an adequate voltage rating, but if the generator neutral is grounded in the wrong place or you make any mistake, you will have a very bad day, or worse.

[OriginalMuscian]

Thanks for the warning.  I'll have to figure out the grounding issue, as I notice my generator has a couple of different ways it can be grounded.

My probes were delivered to the wrong address, and somebody finally returned them to my mail box. So I have probes now! Here's my high voltage probe:

http://www.ebay.com/itm/121756895609

And here's a picture of my new scope hooked up to my 1x probes:

[oldway]

To measure the waveform of your generator, use a transformer with insulated low voltage secundary (12V for example)...this is far more secure and there is no problem of grounding anymore.

[Ian.M]

That's a no-name, probably Chinese probe.  Before trusting it for high voltage work, inspect it carefully, load the scope end with a BNC chassis socket with  1Meg || 30pF across it (*NOT* a scope or other delicate , ground the shell and do a thorough high voltage insulation test, with the test voltage applied to the probe tip, paying particular attention to testing for flashover everywhere around the probe body from the Earth lead back to the cable.

It should read as 100Meg leakage resistance, and as long as it remains in good condition and is retested regularly, I'd trust it up to the insulation test voltage, but not for CAT II or higher work.  i.e. nothing on the mains side of any equipment fuse.

OTOH if it can be traced to a western manufacturer, you can probably trust its ratings.   Remember, improving paper 'specifications' doesn't cost anything in China unless it directly harms a party official or their family, or they get caught out and loose a big sale.

[tautech]

That's a no-name, probably Chinese probe...... 

Hardly.

It's from the YPiIONEER range of which the P6000 range is the most common.
Specs:
http://www.ypioneer.com/htmlmodel/cpxx/12564336.html

[Ian.M]

Well I hope I can be pardoned for making that mistake as I found what appeared to be the same probe listed under three different brand names, shipping from China., and you've just added a fourth.    That makes it very hard to tell if its a genuine OEM item produced for any of the brand names, from a ghost shift run or is from 'gongkai' design sharing. 

What should OriginalMuscian check to be sure he hasn't got a cheap and possibly dangerous knock-off?

[tautech]

Well I hope I can be pardoned for making that mistake as I found what appeared to be the same probe listed under three different brand names, shipping from China., and you've just added a fourth.    That makes it very hard to tell if its a genuine OEM item produced for any of the brand names, from a ghost shift run or is from 'gongkai' design sharing. 

What should OriginalMuscian check to be sure he hasn't got a cheap and possibly dangerous knock-off?

Pardoned, of course, you were not aware of YPIONEER, most aren't.
It is not a widely known name, however the many million P6100 probes they have made are.
I can assure you the brand name is OEM and re-branded or sold as the OEM probe for many Asian equipment suppliers. I'll add that as most resellers of any product attempt to keep their suppliers secret, it is not at all surprising to find the same product available from several sources.


The probes in question are another thing, they are not your "run of the mill" units, 100:1, 2kV probes rarely are.
That the manufacturer lists extensive specs should offer some confidence.

Copies of their probes might be another thing    as most probes from many equipment supplies never state the original probe manufacturer, so yes how would one know?
As with much Asian supply one can only search out those suppliers with good ratings.

FYI
I have sold dozens of YPIONEER P6100 probes without problem.
It's a brand I'm confident with.