A teardown of the HP 8620C and HP 86245A by Kerry Wong:
I just picked up an HP 8620C sweep oscillator with an HP 86245A 5.9 GHz to 12.4 GHz RF plugin on eBay. This time around though, the unit does not work. While it was advertised as a working unit I could not get it powered on and there was no sign of life whatsoever. So before I start troubleshooting and repairing the unit, I thought I would do a quick teardown to see what’s inside and if I could spot anything obvious that was out of the ordinary.
I recently bought an HP 8671A microwave frequency synthesizer on eBay. This synthesizer can generate signals from 2GHz to 6.2GHz with an unleveled output of more than 8dBm. It is a nice complement to my HP 8642B signal generator and Wavetek 907 signal generator. Using these generators, I can now generate signals of pretty much any frequencies under the 12GHz range. A video of this teardown is linked towards the end of this post.
Kerry Wong writes, “In my previous video featured on EEVBlog I did a teardown of an HP 493A microwave amplifier along with the traveling wave tube inside. I actually had done a teardown of an identical unit a while ago but this time I managed to take a peek at the traveling wave tube inside.”
As I mentioned in one of my posts a few years back, a color analyzer from the 80’s can be a treasure trove for the hobbyists. And at the very least, it is a cheap way to get yourself a photomultiplier along with the supporting circuitry to do experiments with. For instance, you can utilize the fast response time of a PMT to do accurate speed of light measurement in a lab setting like I showed in this experiment back in 2015.
I just bought another one off eBay, and this time it is a Beseler PM1A color analyzer. By the look of it, it is probably a cheaper version of the Beseler PM2L I did a teardown and reverse engineering with before.
Upon removing the glass bulb enclosure, I was a bit surprised to see that only two power LEDs were used in this Cree bulb. Typically, you would see many more lower wattage LEDs put together to achieve higher wattage ratings. The two power LEDs are wired in series. Each power LED likely consists of eight to ten LED dies inside as the forward voltage drop of these two LEDs is measured at around 70V in operation, with each dropping around 35V. There is also a reverse polarity protection diode integrated into each of these power LEDs.
Recently I obtained a Sense Energy monitor via US from Margaret of BitKnitting. She is doing a very interesting neighbourhood energy efficiency project. As usual I could not contain my curiosity and opened it up to have a look. I will start off with an analogy – the closest bit of open-source kit that I have to do half the amount of analog functions as the Sense is the PRUDAQ on the BeagleBone wifi
This is a highly specialized instrument, all it does is measuring low ohm range resistance (from 200mΩ to 2000Ω in five ranges) and nothing else. The meter came with a rugged case which is handy for field use, although its portability is hampered by the requirement of a wall outlet.
Since this meter is designed for low resistance measurement, it came with a set of 4 wire Kelvin clips. The stock leads are not my favorite though, as the design uses rubber rings to hold the two clip pieces together. One issue of this (instead of proper spring tensioned clips) is that the tension is quite weak and it is difficult to make secure contact with small dimension leads. Also, the rubber ring is likely to lose tension and fail over repeated use.
The ATVR-1000D utilizes a motor to drive the wiper of a autotransformer (Variac), the servo motor can be driven in either direction depending on the output from the OpAmp (LM324) based comparator. Comparing to a voltage regulator that uses relays for tap-switching, this type of servo-driven voltage regulator has several advantages. It offers continuous voltage adjustments as opposed to the limited discrete steps offered by relay-switching regulators. Also the output waveform is continuous.