Need more Information on Set of Oscilloscope Probes (PB39) - Page 1
Forum section: electronics / testgear

author: exit_failure
author_rank: Regular Contributor
timestamp: January 06, 2022, 06:19:57 pm
content: I got a hold of two pairs of 10x "PB39" oscilloscope probes included with a bunch of other stuff. Unfortunately, I can’t find any information on them. I also do not recognize the manufacturer’s logo. Each of them has adjustment screws at the BNC-connector. One with a yellow and one with a black plastic surround inside the hole. Them seem to be well made. I've attached a couple of photos of the probes.Does anybody have any technical data on these probes or at least recognize the logo on them? Are they anything special?

author: bdunham7
author_rank: Super Contributor
timestamp: January 06, 2022, 06:52:48 pm
content: The logo is of Gould Electronics. A search for "Gould PB39" doesn't yield much except for someone selling a Gould oscilloscope with 4 PB39 probes. He claims to have the manual for the probes (you could ask if the listing I scraped up isn't ancient) and that they are x10, 100MHz, 600Vpk. So probably a solid basic probe but nothing extraordinary.https://astromart.com/classifieds/astronot-garage-sale/astronot-non-astronomy-items/show/gould-1624-20mssec-digital-storage-oscilloscope

author: exit_failure
author_rank: Regular Contributor
timestamp: January 06, 2022, 07:17:49 pm
content: Thank you.Unfortunately, the listing is from 2014 and marked as sold but the information you dug up is already plenty. The listing calls them "differential probes" but they are just normal passive probes, if I'm not completely mistaken.The only thing I couldn't find out was, what the second adjust is most likely for. Any ideas?

author: exit_failure
author_rank: Regular Contributor
timestamp: January 08, 2022, 12:26:31 pm
content: I thought about it again:Since the probes are advertised as "differential" probes, the second adjustment most likely is a variable resistor for exact input attenuation matching. They most likely were used with differential amplifiers and the like. Which makes sense since they are physicality attached pairwise with a plastic sleeve around the cables.

author: alm
author_rank: Super Contributor
timestamp: January 08, 2022, 01:20:01 pm
content: I'm guessing they will indeed be similar to the TektronixP6055orP6135/P6135A. Maybe those manuals will be of any help? Of course it won't help you with any technical data like bandwidth or input capacitance compensation range. For the latter you can just try compensating them to your scope, and if you can get a nice square wave from the probe compensation output, than clearly your scope is within the compensation range.For testing bandwidth you'd have to search for ways people use to test scope bandwidth. If you have access to a say 100 MHz sine wave signal, and you have a scope and other probes that have a bandwidth well beyond that, you could compare the two probes and estimate the bandwidth of the Gould probes. If the attenuation is the same or less, the bandwidth is clearly more than 100 MHz. If the attenuation of the amplitude is about -3 dB, the Gould probe might be roughly 100 Mhz, etc. An alternative would be a very fast rising / falling edge, likethis]https://www.eevblog.com/forum/testgear/fast-rise-time-2ns-or-1ns-signal-generator/]thisorthis. In this case it would be about testing probe bandwidth, not scope. The latter is quite overkill.As for input capacitance, you could either use an LCR meter that can measure that low, or you could measure the crystal frequency, add a probe with a known input capacitance and observe the frequency shift, then replace it with the unknown probe and get a qualitative measure if the input capacitance is higher or lower. You could add more "known capacitance" probes to try to equal the unknown probe. Note that probe input capacitance is specified when attached to a 1 MOhm scope input.