Test-Gear

The HP/Agilent 6632B is a remarkable power supply. There are some similarities with the mobile communication DC source 66309D I “repaired” recently: The 6632B is optimized for a fast transient response and it has a low current range too. But the circuit and its properties differ significantly. One important aspect: Where the 66309D only has a downprogrammer that doesn’t track the current setpoint, the 6632B goes all-in: It’s a two-quadrant power supply - able to source and sink current over the full operating range from 0-20V at 0-5A in CV and CC mode. ...

A few days ago I got my hands on a faulty Agilent 66309D Mobile Communication DC Source. To be honest, I don’t think I need it, but it was pretty cheap and I was looking for something to either repair or potentially salvage the case of. The Mobile Communication DC Source is a specialized power supply. It not only has an improved transient response, but also a few other features not found on standard power supplies (e. g. E363x, E364x). The list for the Agilent 66309D includes (not necessarily exhaustive): ...

Currently, the unit’s setpoint accuracy isn’t all that great (readback resolution is limited as well, but shows the offset): Regardless of the range it has an offset of about +20 mA. Sure, for a unit capable of 60 A that seems reasonable, and well within its specs of ±0.1% ±75 mA. But since I’ll use it in the low range (6A) most of the time and likely often even well below 1A that doesn’t seem too great, does it? ...

I recently got my hands on a HP 6060B System DC Electronic Load (later also sold as Agilent 6060B). My unit has option 020 installed: Comically large binding posts also on the front panel. This option certainly is not unheard of, but not too common either. Retrofitting is possible, but can be quite some work. Huge binding post also on the front panel thanks to option 020 ...

Many older HP/Agilent instrument share a similar feet design. There are at least two different types though: One with a metal part to prop up the instrument and one without it that can be used on all four corners. The feet can be detached from the instrument, e. g. for use in 19" racks. This also means they got thrown away too often, so that many used instruments come without them. For some time they were available on ebay at a reasonable price. ...

Almost two years ago I bought a Brymen BM789 Multimeter. And there is a lot to like about it. It has great specs, is feature-packed, feels high-quality and yet it’s well priced. But there are also some mostly minor aspects I don’t like: The segments of the display on my unit vary in contrast slightly but noticably - especially with backlight - like the zebra strip wouldn’t provide the best connection. It’s not that. You might be able to see it on the cover picture. With the backlight enabled and depending on the viewing angle, the contrast isn’t too great either, a characteristic it shares with many other multimeters (Hello Fluke 170 series) Brymen had to ship multiple versions of the firmware to fix some issues, some of which might have to do with part tolerances and therefore aren’t relevant for all units. The current version is 78911, mine was one of the earlier units and shipped with version 78905 - supposedly the first mass-deployed firmware. I didn’t notice any issues on my unit and many of the problems are likely solved by now. To change the fuses you have to open the meter (like with many, but not all other meters) My personal opinion: The Fluke 170 series is easier to work on. But it doesn’t have nearly as many features either ( and therefore components and boards) My main issue though and this is not limited to Brymen (hello Hameg, Rohde & Schwarz, Keysight): I couldn’t find any calibration/adjustment procedure. In my case I’m interested in calibrating and adjusting the low DC and AC voltage ranges. Given an adjustable and reasonably low noise source and a decent (calibrated) 6.5-digit multimeter this is something even more serious hobbyists could do reasonably well. It’s possible to figure out how it’s done, but why did I have to? Didn’t I buy the meter? ...

The other day I noticed an issue with one of my Agilent 34401A’s: I measured a constant DC voltage and after a few minutes the measured value would start dropping and become unstable. Then I got curious and checked the two-wire resistance mode. Same story, maybe worse. A word of caution: High voltages found inside the DMM can cause damage, severe injury or death. If you are not authorized or qualified to work on such devices, don’t do it. I don’t take any responsibility for actions you take or the results of these actions. You do everything at your own risk. ...

For engineers analog oscilloscopes are a bit like vinyls and tube amplifiers: Most don’t use them anymore, but if they see one, they think: Nice! And are happy that they don’t have to deal with them on a daily basis ;) However, I bought a Tektronix 465B with a faulty second channel, just to repair it. For this one, I made a quick YouTube video. ❗ Caution High voltages found inside of analog oscilloscope can cause damage, severe injury or death. If you are not authorized or qualified to work on such devices, don’t do it. I don’t take any responsibility for actions you take or the results of these actions. You do everything at your own risk. ...

I briefly mentioned the Siemens B2086 Decade Resistor in the previous post. In this post I want to provide additional information on this interesting “vintage” unit, which seems to be geared towards AC application, not just DC. I couldn’t find a date code on it. However, back in the day they published proper manuals including part lists and schematics (yes!). Those are from 1975 to 1981, so it could very well be 30+ years old. ...

With the availability of affordable precision resistors it has become fairly easy to build a diy “resistance standard” that is more than good enough for (most) hobby use cases, e. g. checking DMMs and comparing them with each other. So a while ago I built a simple enclosure for such a precision resistor with 4-Wire (4W) measurement terminals. 2-Wire (2W) measurements are important to me as well, because most handheld DMM don’t feature a 4W measurement. That being said, both their resolution and accuracy are pretty limited, so that I wouldn’t consider the 2W measurement all that critical. ...