4 ms·

Repairing an HP 5370A Time Interval Counter

30 points by thomasjb 1y ago

monocasa 1y ago
What an incredibly Curious Marc esque blog post. And I mean that in the best possible way. : )
- tverbeure 1y ago
  Thanks! But I hope not I'll never blow up a high voltage supply because I have no ambition of fixing that.
Tempest1981 1y ago
Love those giant capacitors! And beefy HP-IB connector.
mlyle 1y ago
I love the old HP app note linked: https://ilrs.gsfc.nasa.gov/docs/time_interval_measurements.pdf https://ilrs.gsfc.nasa.gov/docs/time_interval_measurements.p... The fact that we have this discussed in the open, in such a transparent way, is great. HP was confident they could maintain their lead while talking about methodology and design. The marketing value of open communication to showcase their leadership (and to enable engineers using their products to learn to do similar things outside of the test space) was evident.
- tverbeure 1y ago
  If you haven't already, you should also check out the HP Journal edition that was dedicated to this counter: http://www.hparchive.com/Journals/Low-Resolution/HPJ-1978-08-Low-Resolution.pdf http://www.hparchive.com/Journals/Low-Resolution/HPJ-1978-08....
  - mlyle 1y ago
    This is really great. Bummed I didn't see it before. I made a really precise timebase and a fairly precise interval counter a decade ago using pretty different techniques (ECL and staggered delay lines and a lot of calibration). It would have been nice to know more about these techniques.
    - tverbeure 1y ago
      I've been wondering if it's possible to recreate this with today's technology. The HP implementation uses a custom ASIC with very fast transistors, so it's not obvious. https://febo.com/pipermail/time-nuts_lists.febo.com/2025-July/109936.html https://febo.com/pipermail/time-nuts_lists.febo.com/2025-Jul... If you want to make your own interval counter today, the to-go-to method is to use a TDC7200 chip. If that's not good enough, you can also look at the schematics of an SRS SR620 time interval counter. It has a similar 25ps precision and uses an ADC to interpolate between samples of a 90 MHz clock. These kind of ADCs weren't available in 1978.

30 points by thomasjb 1y ago

monocasa 1y ago

What an incredibly Curious Marc esque blog post. And I mean that in the best possible way. : )

tverbeure 1y ago
Thanks! But I hope not I'll never blow up a high voltage supply because I have no ambition of fixing that.

Tempest1981 1y ago

Love those giant capacitors! And beefy HP-IB connector.

mlyle 1y ago

I love the old HP app note linked: https://ilrs.gsfc.nasa.gov/docs/time_interval_measurements.pdf https://ilrs.gsfc.nasa.gov/docs/time_interval_measurements.p... The fact that we have this discussed in the open, in such a transparent way, is great. HP was confident they could maintain their lead while talking about methodology and design. The marketing value of open communication to showcase their leadership (and to enable engineers using their products to learn to do similar things outside of the test space) was evident.

tverbeure 1y ago
If you haven't already, you should also check out the HP Journal edition that was dedicated to this counter: http://www.hparchive.com/Journals/Low-Resolution/HPJ-1978-08-Low-Resolution.pdf http://www.hparchive.com/Journals/Low-Resolution/HPJ-1978-08....
- mlyle 1y ago
  This is really great. Bummed I didn't see it before. I made a really precise timebase and a fairly precise interval counter a decade ago using pretty different techniques (ECL and staggered delay lines and a lot of calibration). It would have been nice to know more about these techniques.
  - tverbeure 1y ago
    I've been wondering if it's possible to recreate this with today's technology. The HP implementation uses a custom ASIC with very fast transistors, so it's not obvious. https://febo.com/pipermail/time-nuts_lists.febo.com/2025-July/109936.html https://febo.com/pipermail/time-nuts_lists.febo.com/2025-Jul... If you want to make your own interval counter today, the to-go-to method is to use a TDC7200 chip. If that's not good enough, you can also look at the schematics of an SRS SR620 time interval counter. It has a similar 25ps precision and uses an ADC to interpolate between samples of a 90 MHz clock. These kind of ADCs weren't available in 1978.