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Welcome back, Jeff Keyzer AKA Mightyohm!
- Jeff has been consulting, including back at Valve working on a part of the Steam Deck
- CES Con-Flu
- Dead projects
- Sirenza Microdevices
- Portfolio sites – Dave’s friend Steve Hale has been documenting for decades!
- RIFA caps
- Jeff had to replace them to get his HP35665A working
- RIFA – “Replace If Found Always”
- X class capacitor
- The HP35665A is good for lower frequency analysis, including shock and vibe
- App notes
- Dave made a video about Coherence recently that was in this realm
- Kemet / Yageo still makes RIFA
- Modal Analysis
- Charge amplifier
- Voltage dependence of capacitors
- Jeff has been trying to attend events that are able to happen in Seattle, like the recent 3H holiday party
- Museum in Bellingham – Spark museum
- James Lewis talks about bandwidth vs sample rate on a recent video
- Bunnie writes about “Fixing a small corner of the supply chain”
RIFA capacitors, like all capacitors, have a finite life, and then should be replaced. Yes still make the same way but with somewhat improved encapulants, but they do, while new, still pass the safety standards.
Just that you need to replace them after a few years, like electrolytic capacitors, because they are still going to degrade with time and heat.
Polypropylene capacitors are still incredibly common in mains use, where they are self healing, but they still will fail there after a while because of self healing, and all the better brands build in a self disconnect feature in the large motor run ones, so the capacitor will blow it’s terminal connections off when it starts to fail. Still have seen many that failed in other ways, generally involving a section on the side melting it’s way out of the side of the case, and then dripping all over. Paper filled ones still are common, generally in steel cans, and filled with palm oil as dielectric, as they can survive where no plastic does.
Rich W says
I highly recommend the two mentioned museums.
At the connections museum, various switching systems are working, and you can make calls and listen to the relays clicking all around you.
While you’re at it, visit the Georgetown steam plant, an early power generation plant open for exploration (currently closed 🙁 but you can look at pictures)
The first voices which informed about RIFA capacitors started to emerge around 2000.
Sometime between 2005 to 2010 in hobby electronic forum the standard suggestion was to replace every transparent-yellow thing labeled RIFA when a electrical appliance with mains cable was to be repaired.
Dave mentioned an Appnote from Tek (?) that explains the 2.3 x sample rate. Unfortunately it’s not in the shownotes and I can’t find it online. Where is this number coming from? It is mentioned e.g. here: https://dl.cdn-anritsu.com/en-us/test-measurement/files/Technical-Notes/White-Paper/11410-01138B.pdf on page 9, but without an explanation.
Dr. Joel DUNSMORE says
Of course any mention of the HP 8753 requires some illumination:
The low end of the 8753 is -specified- to 30 kHz but actually operational to 10 kHz. That 300% lower than specified, and until recently represented the widest BW VNA on the market (wide means ratio of max to min frequency).