Uploaded May 2024 | Updated September 2026, 1 week ago

---

We restore more HP 9895A dual 8" diskette HP-IB drives, but these will be way more challenging. We'll need a full on logic analyzer assisted repair to debug a really, really nasty fault. It's a long video, but don't miss the intermission where Master Ken inspects a transparent silicon-on-sapphire chip!

Many thanks to HP enthusiast Craig Ruff for the ROM dump and disassembly.

Part 1: HP 9895 Restoration so we can play Colossal Cave
youtu.be/SjLRsJzS57Q

8" Floppy Playlist: youtube.com/playlist?list=PL-_93BVApb59tOBmcSGTdc79zuEgp6MxF&si=FWBA4AhHjoQ964gh

HP 9825 Playlist: youtube.com/playlist?list=PL-_93BVApb58Hy846J52DT8FeF9USYJUn&si=ubr1GO7EtGn5h8Iy

Ken's Silicon-on-Sapphire chip blog post: righto.com/2023/12/HP-silicon-on-sapphire-phi-chip.html

Stuff that supports the channel:
- Amazon links for the tools I use in the lab: curiousmarc.com/amazon-links
- Channel merch on Fourthwall: curiousmarc-shop.fourthwall.com
- Legacy channel merch on Teespring (I don't have everything transferred to Fourthwall yet): teespring.com/stores/curiousmarcs-store
- Support us on Patreon: patreon.com/curiousmarc

"Elevator Music" Credit: Crinoline Dreams by Kevin MacLeod

Our lovely sponsors
- PCBWay: fast turn PCBs, pcbway.com
- Electro-Rent: electrorent.com
- Keysight: test instruments: keysight.com
- Samtec: connectors: samtec.com
- R&D Microwaves: rdmicrowaves.com

Get more technical info on the companion site: curiousmarc.com
Contact info: youtube.com/curiousmarc/about