Probe Master Differential Probes: Anyone used these?

[kg4arn]

Does anyone have experience with and/or care to comment upon the Probe Master Differential Oscilloscope probes?

http://www.probemaster.com/product_info.php?cPath=21&products_id=65
http://www.probemaster.com/product_info.php?cPath=21&products_id=64
http://www.probemaster.com/index.php?cPath=21&osCsid=37934d7cfc17dbca8445ad6c962da61c

I have had generally good experience with their Passive Oscope probes.
Trying to decide on spending the extra money for Agilent or not.
Use is hobby not commercial.

[mahwe]

locks like testec could help you to search
the question is who produce it
http://www.reichelt.de/Tastkoepfe-und-Zubehoer/TT-SI-9010/3/index.html?;ACTION=3;LA=2;ARTICLE=132888;GROUPID=4043;artnr=TT-SI+9010

[andyb]

As far as I can tell, Lecroy uses them as the OEM for their hv diff probes. I have one sitting on my bench, I'm in the middle of a repair / reverse engineer. I'm headed out of town for the weekend, but maybe I can put up a photo of its guts. It is pretty well made, tons of shielding, good separation. Unfortunately all the chips are obfuscated.. but otherwise, not too bad - plus I got it in non-working condition for $20...

[andyb]

Teardown / repair here

http://bardagjy.com/?p=1664

[Mechatrommer]

Teardown / repair here
http://bardagjy.com/?p=1664

good job thanks. but can you post the back side of the pcb? or if it isnt too much and easily dismantled, the back side of the second layer pcbs, there are two on each side with many smd resistors on it. i believe its equally important to know even if there is no component there.

[kg4arn]

Many thanks andyb

[nctnico]

I recently bought this one from Ebay:
http://www.ebay.com/itm/180839240171

Works just fine. The same seller also has 50MHz version. I like the fact it has a mains adapter. I hate equipment running on batteries. They're always empty when its most inconvenient.

[andyb]

Attached image of the back side. Nothing really to see there.

Nothing on the back side of the "stacked" boards. Underneath the "stacked" boards are capacitors to compensate the input divider. Many caps in series, probably to increase their voltage rating. I tried to remove those boards, but didn't want to damage it.

[Mechatrommer]

Attached image of the back side. Nothing really to see there.
Nothing on the back side of the "stacked" boards. Underneath the "stacked" boards are capacitors to compensate the input divider. Many caps in series, probably to increase their voltage rating. I tried to remove those boards, but didn't want to damage it.

there is! the ground plane! the other components are bonus this strengthen my belief that ground plane under signal path (input stage voltage divider) is not necessary, and infact will screw something if provided (from my little experience at least). the reason i can think of why they stacked the input stage is maybe due to (1) to isolate input stage from nearby coupling (gnd plane and other components) from HV or CMRR degradation effect or either (2) to save space, but i doubt it since there will be extra manufacturing process for that trivial reason. you dont need to damage your stuff to impress others, your explanation on whats under the stacked board is more than appreciated, thanks. 10x for that.
edit: as someone mentioned. recalibrating this stuff is very sensitive and fiddly, so i guess you need to be careful poking with that naked pcb. YMMV.

[andyb]

Hrm, I'm not sure if there's a ground plane underneath the input resistor divider boards - I don't think so, this needs to be safe - but I'll check the next time I have it open.

The selective removal of ground plane on the bottom side of the (presumably) amplifiers is to minimize stray capacitance. This is a pretty common practice for high performance opamps, and mentioned explicitly in a few data sheets.

[Mechatrommer]

thats what i meant, ground plane under the input stage (under tha stacked pcb)

[underwurlde]

Old post I know but....

I have some of those testTec probes... expensive to say the least so, being bored one day & having a penchant for reverse engineering electronics, I thought I'd have a crack.

As mentioned, all the IC's have their markings scatched off, not making this easy but here goes:

PSU: switched mode based around an NE555 timer.

Diff amp:
14 pin device is... NOT as I initially thought it must be an opamp of some sort but a 5x NPN transistor pack, LM3046
So Diff amp is based around a simple transistor based diff amp arrangement with an added 2N2222 (NPN) and 2N3906 (PNP) etc for constant current using the power LED for vRef

A dual NChl monolithic JFET device provides the link from probes to differential input of transistor stage. *edit* this is an SST441 device. *edit*

The output stage is (I think) a 741 opamp.

Andy

I have a number of these TesTec probles, some that use thp parts and others that use smt.