Epic HP-9825 repair video series

[BobVA]

"CuriousMarc" is up to part eight (!) of a video series on repairing an HP9825 damaged by a power supply failure.

Besides the 9825 specifics, it's an excellent tutorial on troubleshooting TTL / DRAM-based systems, and there's lots of nice vintage HP test equipment to look at. (Made me a little nostalgic for the ThinkJet I parted ways with in my last move!)

He also posted an interesting companion video where he explains the (free) logic simulation program (LogiSim Evolution) he uses to model the 9825 memory refresh logic.