Posts tagged ‘Frequency Counter’

Keithley 775A Programmable Counter TCXO Repair

In my last post, I did a teardown of the Keithley 775A programmable counter/timer. And while feeding a 10 MHz signal from my Rubidium frequency standard, I noticed that the measured frequency was significantly lower (9.9981 MHz) than the nominal 10 MHz reading and could not be compensated by adjusting the TCXO fine adjustment screw alone. My suspicion quickly turned to the temperature controlled crystal oscillator (TCXO). Continue reading ‘Keithley 775A Programmable Counter TCXO Repair’ »

Keithley 775A Programmable Counter Teardown

I just picked up a Keithley 775A programmable frequency counter from eBay. Specification-wise, this counter is very similar to the Racal Dana 1992 frequency counter I repaired last year. The Keithley 775A I got came with an additional channel (option 7751) and is capable of measuring frequencies up to 1.3 GHz. Continue reading ‘Keithley 775A Programmable Counter Teardown’ »

Teardown and Repair of a Racal-Dana 1992 Frequency Counter

I picked up a non-working Racal-Dana 1992 Frequency Counter on eBay a few weeks ago. The symptom is that only channel C seems to work correctly and neither channel A or channel B produces any measurements. Since the majority of circuitry is shared among all three channels, it is most likely that the fault is localized within channel A and/or channel B. In this blog post I included many teardown pictures taken during the repair and a video detailing the process is included towards the end. Continue reading ‘Teardown and Repair of a Racal-Dana 1992 Frequency Counter’ »

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. Continue reading ‘HP 5350B Microwave Counter Teardown’ »