We made some unbelievable discoveries about this Plexus P/20!

We are back with the broken Plexus P/20. In this video I talk about some amazing discoveries we've made on this machine which gives me the right information and the tools I need to attempt to repair it.

Part 1:    • What is this rare multi-user UNIX wor...  
Part 2:    • First power up of the Plexus P/20 dua...  
Part 3:    • Booting UNIX on the Plexus P/20 didn'...  
Part 4: This part

00:00 - Plexus Recap
01:23 - Intro
01:40 - Fixing the Reset Fault
10:22 - WTF is Error 4F02?
16:42 - Enter Usagi Electric's Community
18:55 - A Literal Pot of Gold
25:44 - Back to the Community
27:04 - Error 4F02 - No Ram Detected
28:02 - 68000 Memory Management
32:58 - Looking for a Mapper Signal
36:01 - A Huge Smoking Gun
38:36 - Troubleshooting Memory Again
45:06 - Replacing the Flip-Flop (Chip U4F)
50:45 - This is Freakin' Good
53:05 - Trying to Boot Into UNIX
55:17 - What's Next

-- Links

Plexus P/20 Discord channel at Usagi Electric:
  / discord   (Plexus channel)

General Adrian's Digital Basement channel:
  / discord  

My Github Repo (with ROM dumps and images)
https://github.com/misterblack1/plexu...

Plexus P/20 Brochure:
http://www.bitsavers.org/pdf/plexus/b...

Plexus Unix:
http://www.bitsavers.org/pdf/plexus/b...

MFM emulator:
https://www.pdp8online.com/mfm/mfm_ol...

Fujitsu Hard Drive Brochure:
https://archive.org/details/bitsavers...

Omti 5200 Manual:
https://oldcomputers.dyndns.org/publi...

Adrian's Digital Basement Merch store:
https://my-store-c82bd2-2.creator-spr...

Adrian's Digital Basement ][ (Second Channel)
   / @adriansdigitalbasement2  

Support the channel on Patreon:
  / adriansdigitalbasement  

My GitHub repository:
https://github.com/misterblack1?tab=r...

-- Tools

Deoxit D5:
https://amzn.to/2VvOKy1
http://store.caig.com/s.nl/it.A/id.16...

O-Ring Pick Set: (I use these to lift chips off boards)
https://amzn.to/3a9x54J

Elenco Electronics LP-560 Logic Probe:
https://amzn.to/2VrT5lW

Hakko FR301 Desoldering Iron:
https://amzn.to/2ye6xC0

Rigol DS1054Z Four Channel Oscilloscope:
https://www.rigolna.com/products/digi...

Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
https://amzn.to/3adRbuy

TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)
https://amzn.to/2wG4tlP
https://www.aliexpress.com/item/33000...

TS100 Soldering Iron:
https://amzn.to/2K36dJ5
https://www.ebay.com/itm/TS100-65W-MI...

EEVBlog 121GW Multimeter:
https://www.eevblog.com/product/121gw/

DSLogic Basic Logic Analyzer:
https://amzn.to/2RDSDQw
https://www.ebay.com/itm/USB-Logic-DS...

Magnetic Screw Holder:
https://amzn.to/3b8LOhG
https://www.harborfreight.com/4-inch-...

Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
https://www.ebay.com/itm/14-16-18-20-...

RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
http://www.retrotink.com/

Plato (Clone) Side Cutters: (order five)
https://www.ebay.com/itm/1-2-5-10PCS-...

Heat Sinks:
https://www.aliexpress.com/item/32537...

Little squeezy bottles: (available elsewhere too)
https://amzn.to/3b8LOOI

--- Instructional videos

My video on damage-free chip removal:
   • How to remove chips without damaging ...  

--- Music

Intro music and other tracks by:
Nathan Divino
@itsnathandivino