Cheap China P6xxx probes ... good .. bad ?

[calin]

I just scored  recently a Tek 2465 300Mhz on eBay .. and of course has no probes. I am not extremely picky as I will be using the scope for the home/garage lab so I really don't fell like spending big money on probes.   Heck I paid 150$ for the scope with delivery and all.

I wonder if anyone has some experience with  cheap probes from China .. like these for example:

http://www.ebay.com/itm/1PC-150-200-250-300-350-400-Or-500-MHz-Oscillo-Scope-Clip-Probe-Kit-X10-X1-600V-/360940774562?pt=US_Cell_Phone_PDA_Cables_Adapters&var=&hash=item5409bf24a2

@ 15$ a piece for 350Mhz probes ?!!!  [size=78%] good .. bad. I remember I saw I thread a while ago which was saying that they are OK  but it was for the lower frequency ones and I cannot find the thread again .... [/size]

[tautech]

For general work they are fine.
Also their 600V rating is good for piece of mind.
I use them for all my "hack" work and save my best for when it matters.
For the price you won't be disappointed.

[old gregg]

I've four of them since last year and no problems, they're fine for small electronic I guess (all the china low brand scope are delivered with them I think).

[amyk]

Some of them are surprisingly good: https://www.eevblog.com/forum/reviews/cheapest-100mhz-oscilloscope-probes-hands-on-review/
...and some of them are (not?) surprisingly bad: https://www.eevblog.com/forum/testgear/pos-ebay-'scope-probes/

[saturation]

There's are several reviews in the forum archives, good generally < 300MHz, the higher the frequency the more 'iffy' it becomes.  >= 300 MHz, I have doubts about the cheapo ones because at that bandwidth, passive probes typically have 2 compensation adjustments but more importantly, due to loading issues, nearly all have fixed attenuation at 10:1.  for a 300 MHz scope, better to get a 500 MHz probe or it will roll off at the bandwidth as your scope and confuse readings.  IIRC, are ~ no passive probes above 500 MHz.

Two quality low cost options, the Texas brand is consistently good, if you can find it.  Its also sold by Pico Scope for about $80.

http://accessories.picotech.com/passive-oscilloscope-probes.html#TA049

The made in USA Probemaster is great all around 500 MHz probe, a good substitute for OEM.

http://www.probemaster.com/product_info.php?cPath=1_10&products_id=82

That said, maybe there is something new?  But you'd have to be the one to test it for us for cheapos probes > 300 MHz 

[David Hess]

I am dubious about those particular ones being good above 100 MHz but I have a set of Texas TX5125R 250 MHz probes which work well and they are available on Ebay for about $40 each.

Testing a probe is relatively simple if you have a reference flat top pulse generator available to measure the transient response which on the faster probes is adjustable.  This is separate from the probe compensation.

Besides Texas and Probe Master, I would consider TESTEC:

http://www.testec.de/p_tastkoepfe.0.html?&L=1

[calin]

He he .. the ones I was looking @ seems to be the same with the crappy ones ... That means I need something else.


Quote from: amyk on Today at 05:47:46 AM

Some of them are surprisingly good:

https://www.eevblog.com/forum/reviews/cheapest-100mhz-oscilloscope-probes-hands-on-review/
...ant d some of them are (not?) surprisingly bad: https://www.eevblog.com/forum/testgear/pos-ebay-'scope-probes/

[marshallh]

Those are not bad for 100mhz, only downside is they commonly lack a ground spring, and also the tips are not spring loaded and are quite dull/blunt compared to a good probe. So the usable bandwidth you could get with the supplied pieces is maybe 50mhz.

The 200mhz ones aren't terrible but aren't great either. Usually they are 1:100 (not x10) and so yet more noise.

Past that you really don't want to be wasting your time with these. Using passives in general above these speeds comes with all sorts of problems and its better just to make your own resistive probe, which is great for digital

[miguelvp]

Morton controls has UNI-T probes on clearance
http://www.mortoncontrols.com/index.php/clearance.html?limit=all

$32 for a set (2) of 300MHz
$11 for a set of 100MHz
$10 for a set of 60MHz

$19 for a single 1:100 100Mhz

Not sure how good they are and I don't need probes but the 300 ones look nice and they can switch from 1:10 to 1:1
Also I don't own a 1:100 and I don't do high voltage anything so I'm not sure about the HV probe if it's safe or not.

[calin]

Thanks miguel .. that is indeed good deal . I got 4 of them .. @ that price you can't really go very wrong .. Worst case they become spares for my other two 100Mhz scopes. Will see ... I will try to test them .. now I have a good reason to build one of these Jim Williams pulsers ...

[mtdoc]

Morton controls has UNI-T probes on clearance
http://www.mortoncontrols.com/index.php/clearance.html?limit=all

Impressive discounts on some cheap Uni T DMMs as well.

Safety issues aside, for a cheap true RMS meter it's hard to beat a UT 61D for $25.

[miguelvp]

Thanks miguel .. that is indeed good deal . I got 4 of them .. @ that price you can't really go very wrong .. Worst case they become spares for my other two 100Mhz scopes. Will see ... I will try to test them .. now I have a good reason to build one of these Jim Williams pulsers ...

you got 4 pairs or 2 pairs for 4 total?

I'm assuming you got the 100MHz ones, let me know what you think. I'm thinking in getting one pair of the 300MHz ones but quality should be about the same.

[calin]

I got 2 pairs of 300Mhz ones (P060 or something like that) - which makes 4 probes in total - already received them.  First impression is good, nice strain relief , definitely they are and feel nicer than the ones I have for my other scopes.  They come with the little adjustemet screwdriver and some colored tags - no spring tip GND connectors or anything else. I checked them with my 100Mhz scopes , all 4 work a treat and they do seem to actually pick up less noise than the other ones I have .  Seem .. I did not measured. 

Today I am receiving the 300Mhz scope also so I can check them a tad better and see if they really go to 300+ Mhz.  Now where the heck do I find a 300Mhz sig gen for this one off thing? ... The JW pulser is so so to test probe bandwidth.

[David Hess]

The Jim Willams pulse generator is great for testing probes if it produces a flat reference pulse (coaxial charge line) with little or at least known aberrations.  Short of that you need something like a PG506 with its fast rise/fall outputs which are designed specifically for this type of test although they are marginally slow for a 300 MHz probe.

[miguelvp]

I got 2 pairs of 300Mhz ones (P060 or something like that) - which makes 4 probes in total - already received them.  First impression is good, nice strain relief , definitely they are and feel nicer than the ones I have for my other scopes.  They come with the little adjustemet screwdriver and some colored tags - no spring tip GND connectors or anything else. I checked them with my 100Mhz scopes , all 4 work a treat and they do seem to actually pick up less noise than the other ones I have .  Seem .. I did not measured. 

Today I am receiving the 300Mhz scope also so I can check them a tad better and see if they really go to 300+ Mhz.  Now where the heck do I find a 300Mhz sig gen for this one off thing? ... The JW pulser is so so to test probe bandwidth.

Get a cheap FPGA BeMicro CV $50 MSRP but i've seen them selling for $40 via findchip.com and octopart.com. The manual mentions you can run the included memory at 333MHz since it has a speed rate of 8 (which only has a meaning for Altera)

Anyhow, you could flip a GPIO pin at 300MHz with the built in PLLs without a problem. Maybe some cheaper CPLD or older cheaper kit is cheaper but for just a square wave. Or just a PLL and a crystal might do.

I've read methods that you can measure the frequency of your scope without the need of a signal that fast, just don't recall right now how.

Anyway, I'm glad you are happy, today is payday so I think I'll get a pair as well

[David Hess]

Anyhow, you could flip a GPIO pin at 300MHz with the built in PLLs without a problem. Maybe some cheaper CPLD or older cheaper kit is cheaper but for just a square wave. Or just a PLL and a crystal might do.

The problem is getting a clean but fast transition edge to drive a 50 ohm transmission line.  Digital logic has other considerations and one of them is using as slow an edge as possible for a given toggle frequency to prevent excessive ground and Vcc bounce.  ECL or CML has the same requirement but because it is current switched, it suffers less from it and can support faster edges.

A 1 nanosecond transition time for instance would be too slow to accurately test a 350 MHz probe.

[calin]

I got the Tek 2465 in mail ... turn it on .. ws displaying TEST 01 FAIL 10 .. NVRAM cal corrupted or whatever.  I did a DC autobalance and the message went away, everything looks OK but on CH1 and CH2 I have an about 15-20% lower voltage than normal (10V show about 8.2V). I kind of expected the thing to be off as the seller said "it probably needs calibration" .. CH3 and CH4  is bang on; also timebase and trigger are good. Just need to get the voltage on CH1 and CH2 right.



So I may be able to test the probes on the CH3 or 4 .. but I guess tey will have to wait till I calibrate the scope.


BTW .. damn Tek did a nice job with these scopes. I really like it

[David Hess]

Unfortunately calibration on those oscilloscopes is an involved process.  You might want to check here and on the TekScopes@yahoogroups.com email list to see if someone is near you who can help you out and has the calibration equipment.

[miguelvp]

Sorry about the bad news, but at least you got two good channels and I bet you'll get it all calibrated

Here is the operator manual
http://bama.edebris.com/manuals/tek/2465/

and the service manual in here
http://bama.edebris.com/manuals/tek/2465service/

Page 120 has the adjustment procedures.

BTW I went ahead and ordered a set of the 300MHz probes. I don't need them right now but to replace my Rigol's probes it will cost me $70 for one, so I might as well have 2 spares for half the cost

Good luck with your calibration and congrats!

[mtdoc]

I purchased a set of the 300 MHz probes as well- too good a deal to pass up.  Checking them out tonight their build quality does look good and they appear to function well - at least with lower frequency test signals.   I do not have a function generator that goes above 50 Mhz.  I have the parts to build a Jim Williams pulse gen - just haven't gotten around to doing it...

One thing though - while checking the Uni-T probes and comparing them to the Rigol RP3300A probes that came with my DS2072 - I discovered that one of the Rigol probes compensation was off and could not be brought right. In fact the compensation pot did not seem to be functioning correctly- as turning it had little effect.  Looks like I need to send it back to Rigol.  I'm assuming the warranty on their probes is the same as for the scope - 3 years.  I'll be calling them tomorrow.  At least now I have spares...

[calin]

BTW I found a place from where you can get some of the manuals for tek scopes with OCR run over them so you can navigate easier - here http://scopetechniques.com/

[calin]

Here is an update on the status ... Since I had the scope open I decided to measure the power line because I was getting TEST 05 FAIL 40 .. something negative to negative per service manual. Anyways I started checking the power supply and, no surprise at all the -8V rail was more like -6.  A tad of check ... ripple all over. Of course two 100uF caps were "cooked" so replace .. now all supplies are in spec.  (BTW firs usage of my DER 5000 - good tool it already paid for itself) After fix TEST 05 no more fail and I am not getting it anymore .. been abt a hlf day of on - off as I had time to work on the scope.

I also adjusted the screen ... nice sharp traces. I replaced the fan with a silent one. As a prize after the "-8V fix" the amplitude on CH1 and CH2 came to just a smidgen out of spec  .. I guess I might have to do a full calibration. So far I calibrated just the DAC ... point on 2.50004. But I guess my "calibration" saga stops here s I don't have the tools required to go further. If only I can find someone around Phoenix to loan me a calibrator like a PG506 ... fat chance

So far the UNI-T probes work a treat, plenty of room to compensate them so they seem to be working a treat with the 2465. 

[miguelvp]

I should get mine tomorrow, the difference between regular USPS  and 2day USPS was less than a quarter

[calin]

I forgot to mention .. but this may be a surprise to younger players ... The UNI-T probes do not have the "readout pin" so when In 10x mode the scope will not have the "correct" display. This is valid of course if you have issues multiplying with 10


For those interested how to hack and add a readout pin to any probe is darn simple. The pin is nothing else than a voltage divider between the BNC body (the ring around the barrel) and GND (bnc barrel) .. all you need is to put the right resistance between these two points. I found a thread that has really good info what values you need ... So hack away.


http://www.electronics-related.com/sci.electronics.design/thread/116046/readout-pin-on-oscilloscope-probes.php

[miguelvp]

I forgot to mention .. but this may be a surprise to younger players ... The UNI-T probes do not have the "readout pin" so when In 10x mode the scope will not have the "correct" display. This is valid of course if you have issues multiplying with 10


For those interested how to hack and add a readout pin to any probe is darn simple. The pin is nothing else than a voltage divider between the BNC body (the ring around the barrel) and GND (bnc barrel) .. all you need is to put the right resistance between these two points. I found a thread that has really good info what values you need ... So hack away.


http://www.electronics-related.com/sci.electronics.design/thread/116046/readout-pin-on-oscilloscope-probes.php

You probably want to share that link in this thread that just started today
https://www.eevblog.com/forum/testgear/automatic-probe-attenuation-setting-just-a-resistor-(tektronix-tds320)/

My Rigol doesn't have probe id so they will suit me fine since I have to select it manually