Wavetek 907 Signal Generator Teardown

Since I just got myself an HP 5350B microwave counter and I had fixed it up, I thought it would be great if I could get a SHF generator to test out the counter in the microwave range. So when I saw a super cheap Wavetek 907 for sale on eBay, I simply could not pass it up.
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DS3232 Clock Frequency Calibration

DS3232 is an extremely accurate RTC with a guaranteed accuracy of 2.5 ppm (0 °C to 40 °C), which translates into an error of just 80 seconds over the course of a year under the worst case scenario. I had done a few projects using this chip before (you can read about them here).
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HP 5350B OCXO Repair

Last time, I did a teardown of an HP 5350B microwave counter. And as I mentioned in my teardown, the oven-controlled crystal oscillator (OCXO) did not appear to be working as the OVEN indicator would not go off even after hours of use but the counter appeared fully functional otherwise. So I decided to disassemble the crystal oven and see if this problem can be fixed.
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HP 5350B Microwave Counter Teardown

Here is a teardown you do not see very often. I recently bought an HP 5350B 20 GHz microwave counter off eBay. HP 5350B uses harmonic heterodyne down-conversion technique to convert the microwave frequency into the range of its internal low frequency counter. It can measure frequencies from 10 Hz all the way up to 20 GHz via two separate inputs.
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MF 10A Analog Multimeter Teardown

Dave did an analog multimeter teardown in his latest episode. I have a Chinese made MF 10A multimeter bought back in the 90′s and thought I’d do a teardown to take a look at what is inside.
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An Old Tung-Sol Germanium Transistor

I recently bought a few old power transistors from eBay. These are PNP Tung-Sol germanium transistors. According to the date code (6326) these transistors were made back in 1963, long before I was born. The last time I actually used a germanium transistor was more than twenty years ago when I was learning to make transistor radios.
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Keithley 197 Teardown and Repair

A few days ago, I bought a Keithley 197 sold as “unknown working condition” on the cheap. The seller said that some of the keys on the meter were unresponsive. I figured that I’d try fixing it if I could. After all, these 5 ½ meters still fetch well over $100 on eBay and for a fraction of that price, I was willing to give it a shot.
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Server Moved to Linode

I just moved my site from my own server to linode‘s VPS hosting. So you should see some pretty significant performance improvement down the road.
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Backup and Flash Firmware using Arduino

A while ago, I did a tear-down of a Keithley 196 bench multimeter. Towards the end of that post I showed a picture of my breadboard setup for backing up the firmware EPROM (27128) in case I needed to re-flash the firmware in the future. Since then, quite a few people had asked me to provide more details on how to do this using an Arduino. So I thought I would explain a little more here.
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MCP3903 Library

MCP3903 is a six channel Delta-Sigma A/D converter. It features six synchronous sampling differential channels which can be programmed to sample between 16 bit and 24 bit accuracy, the gain for each channel can also be programmatically set from 1 up to 32. It also has an internal low tempco (5ppm/°C) voltage reference, making MCP3903 an excellent choice for digitizing small differential signals from various sensors.
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Modify An Off-the-Shelf CP2102 Module As An Arduino Programmer

A while back, I wrote an article on how to use a CP2102 USB/UART converter chip in place of an FT232RL to program an ATmega328P using Arduino bootloader. Of course, not everyone has the time or wants to build one from scratch. And since CP2102 is offered in QFN package only, it is a big pain to solder without a proper adapter board and decent soldering equipment.
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Arduino Library For LTC4151

LTC4151 is a high voltage I2C current and voltage monitor. It is capable of monitoring input voltage ranging from 7V to 80V with the onboard 12-bit ADC. It can also measure the high side current and an additional external voltage with the same 12-bit ADC resolution. Besides LTC4151, LTC4151-1 and LTC4151-2 have split SDA (SDAO and SDAI) for interfacing with Opto-Isolators.
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HP 436A Power Meter Teardown

HP 436A is a power meter capable of measuring RF power between -70 dBm and 44 dBm (roughly between 0.1 nW to 25 W) with a frequency range from 100 kHz all the way upwards to 110 GHz depending on the sensor module selected. This power meter was made in the early 70′s and has long been discontinued.
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A Digital Thermometer Hygrometer With Analog Displays

It seems that you can’t visit to a microcontroller website without seeing a digital thermometer/hygrometer build of some kind. After all, it is pretty easy to build and at the same time quite useful as well. In this post, I will show you yet another thermometer/hygrometer build. But instead of using an LCD or 7 segment display for the output, I decided to go retro, using two “needles” to display the temperature and humidity readings instead.
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BJT In Reverse Avalanche Mode

Transistors operating in their avalanche regions are often used to generate fast rise pulses (see avalanche pulse generator using 2N3904). Many transistors can also avalanche when the connections to collector and emitter are reversed. When operating in reverse avalanche region, these transistors are sometimes referred to as negistors.
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