Get the latest tech news
Repairing an HP 5370A Time Interval Counter
- Introduction - Inside the HP 5370A - High Stability Reference Clock with an HP 10811-60111 OCXO - RIFA Capacitors in the Corcom F2058 Power Entry Module? - 15V Rail Issues - Power Suppy Architecture - Fault Isolation - It’s the Reference Frequency Buffer PCB! - The Reference Frequency Buffer Board - Fixing the Internal Reference Clock - Fixing the External Reference Clock - Future work - Footnotes Introduction I bought an HP 5370A time interval counter at the Silicon Valley Electronics Flea Market for a cheap $40. The 5370A is a pretty popular device among time nuts: it has a precision of 20ps for single-shot time interval measurements, amazing for a device that was released in 1978, and even compared to contemporary time interval counters it’s still a decent performance.
Once inside, you can see an extremely modular build: the center consists of a motherboard with 10 plug-in PCBs, 4 on the left for an embedded computer that’s based on an MC6800 CPU, 6 on the right for the time acquisition. OCXOs are supposed to be powered on at all time: environmental changes tend to stress them out and result in a deviation of their clock speed, which is why there’s a “24 hour warm-up” sticker on top of the case. More than 10 years ago, the HP5370 Processor Replacement Project reverse engineered the entire embedded software stack, created a PCB based on a Beagle board with new firmware.
Or read this on Hacker News