I'm really scared to turn the TRS-80 Model II on

This is the Part 4 of the TRS-80 Model II "Left for dead" series. In this video, I give the power supply some attention. You cannot power up this power supply without appropriate load, so I decided to give it a full inspection to ensure all the components are within spec. Then, it's time to reassemble the machine and then test it out. Does this left for dead machine work?
Part 1: • Another left for dead ...
Part 2: • I actually got somethi...
Part 3a: • This is how to use an ... (using 8" drives on a PC)
Part 3b: • This is how floppy dri... (all about termination)
Part 4: This part!
Part 5: • I fixed the TRS-80 Mod...
Part 6: • How to fix a Keytronic...
Part 7: • Using an $25 Gotek flo...
--- Video Links
TRS-80 Model II manuals:
electrickery.hosting.philpem....
TRS-80 Model II Github Archive:
github.com/pski/model2archive
Adrian's Digital Basement ][ (Second Channel)
/ @adriansdigitalbasement2
Support the channel on Patreon:
/ adriansdigitalbasement
-- Tools
Deoxit D5:
amzn.to/2VvOKy1
store.caig.com/s.nl/it.A/id.16...
O-Ring Pick Set: (I use these to lift chips off boards)
amzn.to/3a9x54J
Elenco Electronics LP-560 Logic Probe:
amzn.to/2VrT5lW
Hakko FR301 Desoldering Iron:
amzn.to/2ye6xC0
Rigol DS1054Z Four Channel Oscilloscope:
www.rigolna.com/products/digi...
Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:
amzn.to/3adRbuy
TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)
amzn.to/2wG4tlP
www.aliexpress.com/item/33000...
TS100 Soldering Iron:
amzn.to/2K36dJ5
www.ebay.com/itm/TS100-65W-MI...
EEVBlog 121GW Multimeter:
www.eevblog.com/product/121gw/
DSLogic Basic Logic Analyzer:
amzn.to/2RDSDQw
www.ebay.com/itm/USB-Logic-DS...
Magnetic Screw Holder:
amzn.to/3b8LOhG
www.harborfreight.com/4-inch-...
Universal ZIP sockets: (clones, used on my ZIF-64 test machine)
www.ebay.com/itm/14-16-18-20-...
RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)
www.retrotink.com/
Plato (Clone) Side Cutters: (order five)
www.ebay.com/itm/1-2-5-10PCS-...
Heat Sinks:
www.aliexpress.com/item/32537...
Little squeezy bottles: (available elsewhere too)
amzn.to/3b8LOOI
--- Links
My GitHub repository:
github.com/misterblack1?tab=r...
Commodore Computer Club / Vancouver, WA - Portland, OR - PDX Commodore Users Group
www.commodorecomputerclub.com/
--- Instructional videos
My video on damage-free chip removal:
• How to remove chips wi...
--- Music
Intro music and other tracks by:
Nathan Divino
@itsnathandivino

[@csbruce]

5:12 Never noticed before - multimeter model "121GW". Great Scott!

[@jeremiefaucher-goulet3365]

Yes, I have the same one. Many youtubers bought it from Dave Jones like Adrian. It's a really great multimeter.

[@Dave5281968]

The fails lead to diagnostics that lead to understanding and insights that lead to wins. This type of video is great to see. Now I'm anxiously awaiting the diagnostic and repair video!

[@bobvines00]

Ditto!

[@BlackEpyon]

Time to whip out the logic analyzer and see if anybody's home.

[@jonathankent5898]

I just found your channel. My old C64 has sat dormant in my garage for nearly 30 years. I've been wanting to resurrect it for about a month now. Thanks to your advice from your C64 videos, it's now back up and running!

[@MatroxMillennium]

You are so much more patient than I am -- If something looks okay after a quick visual I usually plug it right in and just watch for smoke, haha.

[@HighestRank]

Retired Variac liked this comment.

[@twogitsinacar4811]

Run it up on a Variac without any load

[@orbitingeyes2540]

I learned programming on a Model 1 & a Model 3 back in high school. Great to see that some of these old machines still survive. I just cleaned up my slightly newer C-128. Great thinking on the connector reflow. I used to work on 14" HDDs back at Unisys in the late '80s, and those Molex connector joints were a huge problem... we routinely re-flowed them every time.

[@binarydinosaurs]

I too hate that first powerup moment. Prior to this the machine is Schroedinger's puzzle, you can put weeks into restoring and cleaning and things and it could be working perfectly at that point. Stuff can go wrong so very quickly when you hit the switch for the first time though. I recently worked on the only known Positron 9000 (1982, 6809 CPU) in existence after it had lived in a wet shed for decades and been chewed by rodents - some of the chips had disintegrated. Much cleaning, socket replacement, chip replacement, new PSU. Heart was in my mouth when I powered it up for the first time and..... nothing. Excellent video, thankyou for showing this hobby isn't all success :) Cheers, Adrian (Binary Dinosaurs)

[@wolvenar]

I would love to see something on this system. The progress you make etc

[@TheSimTetuChannel]

Given your track record on tricky issues I have no doubt we'll soon learn that IT FREAKING WORKS!

[@Colin_Ames]

I always enjoy your methodical approach to the repair process. The fact that the computer didn’t work means we will get another enjoyable video in the future.

[@MichaelEhling]

26:30 It's this level of understanding and diagnosis that makes watching Adrian work so fulfilling.

[@Eyetrauma]

27:57 Doctor, come quick, Adrian’s having his bubble wrap delusion again!

[@stevendunn264]

I worked for the Radio Shack Computer Center in Omaha, NE in the mid 80's and the tech's always had one or two open on the benches. Brought back a lot of memories. Even then we were selling 386 and 486 machines but Model II and 16's were still used.

[@GabrielWehrle]

Adrian, I just picked up a Model II myself a few weeks ago and stumbled across this series. It's been super informative (especially the last video) as I try to get my machine booting again. I picked up my machine from a friend of a friend who had it sitting in his barn for the last few decades, and it's in mint condition! After reseating a few connectors, the machine came right on! I've been using the last video you made as guidance to get a bootable floppy made, but I've had no luck with getting my DOS machine to write to the 8" disk yet. I'm excited to see the process as you get your machine running again!

[@epremeaux]

Is it possible the absence of the reset switch is holding the machine in a reset state (as in its an NC switch, and pressing it interrupts a pullup circuit which normally holds it out of reset. Thus you have an open circuit on the "run" signal)

[@hrford]

My thoughts too, old computers and embedded systems ran like this either to save money or to fail safe, i.e. no control panel = no run time!

[@IvorySoul696]

I love the idea of the food items as "breaks" in the middle of videos. It feels like a natural way to get the food items in there.

[@benjaminhanke79]

Take your time and bring it back to life, it's so satisfying to watch a repaired machine up and running. In the last ten months I watched CuriousMarc's videos where he repaird his vintage HP 9825 Desktop "calculator" after the failing power supply damaged several components. I was really happy when I saw it working again.

[@Putersdcat]

For the next time you encounter surface rust on the big steal parts that have that greenish gold finish, goto a marine shop, I’m sure their are plenty in Portland, and grab some Zinc Chromate Primer ;-)

[@tassdesu]

Rarely youtubers post their failures. Thanks that you did

[@jameslewis2635]

Nice work getting this far on such a complicated machine. Honestly, while I am pretty confident working on most home computers from the late 80's and onwards, the TRS-80 would just confuse the hell out of me. Rather than trying to replace all those chips that look a bit dodgy off the bat I would try sanding down the legs and using de-oxit for a start and then maybe replacing the sockets if they are looking bad. It's the kind of thing that can't hurt at this stage as if they don't work with that, you were going to replace them anyway.

[@oldschooldude8370]

My roots dont stretch quite this far. What a relic.

[@ObiWanBillKenobi]

I’ve caught up with the videos in this series now. This is now like waiting for the next Star Wars movie! 🍿🤩 Some day soon I will be watching a video where this 1979 computer has been fully resurrected and lives again!

[@markae0]

Thanks for the video! With the test equipment you have, you have a good chance of chasing down what is wrong. Just getting those 8 inch drives working was great, great to see.

[@RetroJack]

This has been an interesting journey - looking forward to the next part!

[@parrottm76262]

I can't imagine the feeling when you turned it on. This Model II journey has been great. So want to see where it ends up. Thanks ADB!

[@BenderdickCumbersnatch]

Fascinating. What a letdown that some chips may be broken. But you did an awesome job repairing this.

[@michaelturner2806]

Getting it all powered on without any smoke is a great payoff already from the care and testing you've put into it. Great progress, and I'm proud of you!

[@aCivilServant]

Adrian, it's great to see the Model 2 getting some love. It and the subsequent Models in the line always seem to get less attention that the Model 1, 3 or 4. Great to see it torn down and built back up stage by stage. Looking forward to the next video in the series.

[@Sir_Uncle_Ned]

You passed the smoke test, and now you have confidence that stuff does actually work for diagnostic purposes. This was a fun ride so far, I look forward to where we go next

[@tonanornottonull7132]

I've got a funny feeling about that +12 rail and the video board. I think the service manual for the Model 2 says that if you see life in the CRT when checking the +12 rail then the issue will likely be the video board itself if you're not getting your sync signals.

[@sfeather7088]

I have No Idea how any of this stuff works....but I am hopelessly addicted to Your channel. Even in Your "Failure".... I LOVE Your attitude, and content. Great Job Sir.

[@Potts1966]

I'm really enjoying your journey with the Model II. I did have a model 1 many years ago and the Model II was a "pie in the sky" super-machine I could never afford.

[@knghtbrd]

Looking forward to the debug on this when you get to it Adrian! That thing is such a beast, and a temperamental beast at that, so I'm eager to see it working at some point in the future.

[@loganjorgensen]

Beautiful restoration on that PSU and mount. Dang that unit has got some weight to it, can see how a drop would be hard on it even though it's so sturdy. Also the editing on this video is really tight and well paced. Interesting project, the vintage stuff sure is specific often, absolutely no slack for any deviation from spec.

[@mogwaay]

Great video and keep the faith, you'll get it up and running, Im sure if it and I'll be really interested to see the journey. This has definitely inspired me to take a look at my poorly Acorn Electron which I need to see if it's power supply board works, thanks!

[@graemedavidson499]

Glad that PSU was okay! Having worked on SMPSUs for years, I’m still fearful when switching on early types. I was tensed up when you flicked that switch!

[@custardo]

That chassis is cadmium plated, which means sanding and sandblasting is a health hazard. Usually to remove cadmium plating, the parts are submerged in an ammonium nitrate solution but i have no idea if this is something you can do safely at home.

[@Morinaka25]

I was to comment this as well when i saw it, cadmium is extreme toxic, you do not want to be sanding this and inhaling it or getting it on your skin.

[@herrbonk3635]

How can one see whether it is cadmium plated or not? The metal looks a little like ordinary brass to me (if that's the English word for mässing), and certainly like materials I have drilled into!

[@Morinaka25]

@@herrbonk3635 Brass is a solid colour, cadmium plating is a yelllow/pinkish type colour, with an almost rainbow sheen to it. I'd recommend just looking up photos of cadmium plating on google images for a better idea of what it looks like, but in person you wouldn't mistake brass for cadmium plating.

[@herrbonk3635]

@@Morinaka25 Ok, thanks! I belive that material is pretty common in computers, isn't it? I think I understand what you mean by rainbow sheen. But still, how do you really know for sure it's kadmium, and not just a little more zink (less copper) in the alloy? I mean, that kind of brass is usually more yellow.

[@herrbonk3635]

@@Morinaka25 (Perhaps the simple answer is that brass is never used in computers and electronics chassis? But another natural question would be, why toxic cadmium on the surface?)

[@feedmyintellect]

27:53 is where the old socketed chip chiropractic session starts. Enjoy! 😁😁😁

[@karlbauer4616]

back in 1986 i was working on the Model 2 selling it for office use to chimney sweeps in Germany, We sold some 200 of them until switching to IBM pc/at. loved the all-in-one design. will check my garage if i still have some of this stuff. hope you get your machine running soon !!

[@Sloxx701]

This will be a fun series to watch if you keep going with it, hope you do. On thing I hate about troubleshooting any type of vintage electronics that use multiple cards stacked like that is that you cant access the boards easily for proper probing without having some type of extender card to bring to board out where you can access everything. Can be a pain

[@winstonsmith478]

Because of the vibrations from the 8" drive, those glue tacked mounting bolts, and how hard they were to get out, I suspect they used Loctite on them.

[@Nas_Atlas]

Adrian should put a dab of hot glue or something

[@michaelterrell]

I scrapped one of these 20+ years ago. It appeared to be 'printer's ink', like we used on the PRC77 military radios at the factory. It is a very thick ink used to mark paper boxes, or for printing presses. We applied it with a syringe, with a blunt needle to secure screw heads on modules that had to be opened. It holds well, but cracks easily to show that something was tampered with.

[@rawr51919]

@@Nas_Atlas or use Loctite

[@scottharris7222]

Have been looking forward to part II of what is bound to be a quite a series. Coffee in hand.

[@kins749]

Amazing job cleaning the whole machine, great progress overall, just the small matter of the logic board!

[@DavePoo2]

I think the fact that Adrian is even attempting to service this monster of a computer is insane.

[@garthhowe297]

Looking forward to your further troubleshooting... it's a lot harder when you don't have a working machine to swap boards with. You need a bus extender card to give you access for testing (I think).

[@pogostix6097]

Excellent video! It's fascinating seeing the curvy, curly, hand-drawn traces when you're so used to angular, computer-done ones. Connectors are especially prone to breaking... my wacom art tablet kinda regurgitated its USB Mini B port a little while ago. And of course it took the solder pads and contacts with it so it can't be fixed... found a workaround, I can charge the battery using a separate device so I can still get art done, but it was very alarming when it wouldn't connect/charge and when I unplugged it it just... came out with the cable.

[@Azlehria]

Is there perhaps room for a panel-mount port? If not, a last-resort repair could potentially be made by running jumper wires from a new PCB-mount port to the _other_ end of the traces, then epoxying the port to the board.

[@Dukefazon]

22:40 - when I'm dealing with exposed high voltage stuff I never use the device, I plug it in into an extension cord with a switch on it set to the off position. I turn on the device, keep my hands away and turn the extension's switch on. If there's anything wrong I just quickly turn off the extension. But maybe it's different here in Europe because we don't have polarity on the mains, ideally the switch switches and cuts both at the same time. Don't worry, this was exciting :) Looking forward the rest of it!

[@adriansdigitalbasement]

yeah for non grounded stuff (2 pin plugs) they are polarized so neutral should always be neutral. You can't totally rely on that though as the outlet may be wired incorrectly. (Mine are not, I have tested them all.) This machine is earthed and it's using a SMPS, so the chassis isn't live .. unlike many of these old TVs I work on.

[@squirlmy]

@@adriansdigitalbasement I really appreciate your knowledge of CRTs and sharing safety issues. There are lots of vintage computer restoration videos on KZbin, but few of them go into CRTs, I'm sure many don't have the knowledge. CRT repair is surely a dying art.

[@midimusicforever]

Grass soda actually sounds nice and quirky at the same time!

[@OldmanGamerYT]

I know you'll get it working! Can't wait to see the next video.

[@justinchampion5468]

As usual a great and fun retro-work video! Also, the grass soda made my skin crawl! I love the smell of fresh-cut grass but I can't imagine drinking it. *Mr Yuck Face*. In any case, thanks again Adrian!

[@adriansdigitalbasement]

It was shockingly better than it seemed!

[@Lee_Adamson_OCF]

I had the same bad solder joints on my PSU as well. If I recall correctly, you have the older style PSU, which may not be beefy enough if you want to add a MC68000 subsystem and run Xenix.

[@kjtroj]

Like you, I wouldn't worry about the cosmetic stuff inside - preventing further degradation and saving it from the land fill is more important. Good to see the progress on this machine! Even if it's not working (yet), it's closer than it was when you got it

[@travmanbrett5338]

I was a radio shack repair tech back in the early 80s and worked on model II s . Just from experience I remember video problems were mostly caused by a failure of the video boards. The CRT ( cathode ray tubes) were very reliable and almost never failed . Earlier comment concerning the bad reset switch is also a possibility

[@transistorbaluba]

thx for the journey.. looking forward for more on this.

[@sfperalta]

Great video series. Fun to watch the diagnostic process and the repair techniques used. Also fascinating to me because I was a TRS-80 user, Model I and Model 4. Back in 1980 I bought the base Model I (16K, cassette storage) because, frankly, it was almost half the price of the Apple ][ that I was looking at -- though the Apple ][ had color output and expansion capability in their base model, unlike the Model I. Eventually I got the Model I expansion module to bring the computer up to 48K (I think... memory is fuzzy) along with a pair of 5.25 inch floppies to round out the setup (much more usable than the cassette interface!!). Funny thing, that fancy configuration made the Model I pretty close to the same cost as a similarly configured Apple ][! The TRS-80 was a good, capable machine and there was enough technical info available for it that I was able to learn quite a bit about computer technology from using it, as well as write many useful BASIC programs to automate my life. Eventually I sold the Model I to buy Model 4P with the integrated floppy drives which could run CP/M as well as TRSDOS. Although the 4P was nominally portable, it was rather more a "luggable" like many of its contemporaries. All in all solid computers, great for learning (though I must admit, the Apple ][ would have been the better investment in the long run LOL).

[@dragonhed123]

Omg so sad to see it didnt work. I hope there will be another video ill be looking forward if it comes in the meantime cant wait for ur next video :)

[@ChrisDreher]

Cool seeing other Astec parts. They are moderately known for making RF modulators parts in old gaming consoles (example: Intellivision gaming console).

[@paulsccna2964]

As a nerd, this was 30 minutes of riveting content. Looking for how the chip fix goes.

[@SimonEllwood]

Maybe add some clear sheet acrylic (Plexiglas, Perspex) over the mains connector block. Great video!

[@BapsyGames]

I like that Power Connector, aesthetically (and logically)... It's keyed in a nice way (2 flats on one side and 1 on the other) ...And I like the shape of the 5 by 3 arrangement :-) edit* Forgot to mention... Nice Video again @Adrian :-)

[@JustWasted3HoursHere]

Man, those things were built like a tank but that explains why they were so expensive back in the day. Things have been massively miniaturized and simplified in pretty much every way you can imagine nowadays.

[@techkev140]

Hey, I've got some of those black and transparent amber looking nut and screw drivers. Got them in a tool set from a high street store here in the UK back in the 90's.

[@systemchris]

It's good to see a video like this, life isn't perfect! Let's hope you find the cause :) and can repair it

[@RylandBingham]

It's kind of nice to see a project result more typical of my own results, lol!

[@EpicureMammon]

I love how dangerous the inside of that computer is.

[@gatomalo3424]

The power supply of that thing is the most scariest thing I've seen

[@georgedyson9754]

I am always amazed that these computers can be assembled cost effectively in the factory!

[@Breakfast_of_Champions]

Wow it's ancient! Just one step short of a real mini. At 40 years plus I'd expect all kinds of failures from it, that's a big restoration job.

[@sheep1ewe]

This is a great restoration, i try to keep my machines as original as possible, but also so they can be used as this, maybe if it has been something extremly special, like the only one in existance it had been different, but honestly all my machines are in reality less than 100$ market value and where made in large series so using rustremover and automotive protecting paint is not a problem here and will do perfect for presvering the machines for the future.

[@lindoran]

Loved this video series 😁

[@RealGengarTV]

It's not a failure, it's just temporarily in a state of disrepair 😜 I'm looking forward to another video down the line of this beast

[@syretia551]

"spider balls" made me giggle lol

[@wanjockey]

2:20 it is called a common mode choke. It cancels out interference that comes in on both the hot and neutral.

[@wizdude]

You need to add the Pinecil to your list of “tools” on the videos now. I saw you using it here. I’d been reading about the Pinecil but it was one of your midweek mail call videos that eventually convinced me to order one. It should be here in a few days! (I got the red case as well so I can make mine look like yours. I agree that colour combination is nice!) Great video btw. I’m a TRS-80 person but never worked on a Model II before. Cheers!

[@wizdude]

@@tspawn35 I also purchased and have just received a wall socket 65W GaN USB-C PD power supply from Amazon. This power supply claims to provide a full 65W and I think it will work beautifully with the Pinecil. I’m looking forward to my Pinecil arrive as well. I have some small projects waiting for me to solder up and I know this will be better than what I currently have as well. Hope all goes well for you too! :-)

[@scharkalvin]

The top slot connector might be warped without being broken. If you can find a replacement connector you can use a solder sucker to remove it and replace it.

[@senilyDeluxe]

That's where the fun starts with getting the system's cards accessible to an oscilloscope...

[@tassdesu]

Cool soda, thanks for the review

[@tcpbox]

Adrian you are a great guy, you do it seems so easy.

[@CrashPilot1000]

Thanks for sharing this thriller!

[@ruediix]

You can likely get off the shelf replacements for those card edge connectors since they are non-keyed. Likely is, of course, not a certainty, but you could try contacting some electronics supply catalogues.

[@ladyqonimvu8604]

add this to my comment. trick learned when I worked on tv repairs. ink mark the top of yoke as alignment mark, before removing it so it can be reset correctly.

[@6581punk]

Fixing this PSU is an Astec Challenge.

[@bloxyman22]

I have had access to electronic recycling waste for a very long time, but I have nowhere near the knowledge like you when it comes to electronic. I found computers from the 70s, tube radios from the 40s and anything in between. Nearly all of my equipment is from recycling center current amplifier I use is a 60s kenwood ka-6100. All equipment I found I just fired up up from the get go if they were dry and not wet from rain. Guess what?? 99.9999% of the time it just works. This amp I am using now has been on 24/7 for years and even bulbs works. I have just never come across something except maybe one "modern" ampilifer that failed because of a capacitor. Even had a osbourne 1 at a time with a bunch of working software, but sadly I was dumb enough to trade it away back a long time ago.

[@rubusroo68]

vintage electronics were death traps, hot chassis, non polarised mains inputs, exposed external b+ terminals, no fuses, asbestos heat shields etc etc

[@aaronjamt]

Quick suggestion: get a set of cheap remote controlled outlets to plug computers, monitors, isolation transformers, etc into. It makes me feel much better powering up old equipment when I can stand a few feet back with a fire extinguisher or whatever when I turn it on. I can also very quickly shut it off if I need to, even if I would normally have to reach over live power cords or bare wires to unplug it. I've also created a mini foot-pedal that allows me to hit the "off" button on the remote with my foot if something goes wrong, also very useful (especially when hands are full with the fire extinguisher).

[@gpiforgoo]

hmmm... I would rather install an emergency button, which shout down the complete power in the room. And be careful with the fire extinguisher - there are different kind, especially when high voltage electronics (like crts) are involved. I this case maybe other factors could be interesting, for example a basement with small windows. Or you want to use something that damage the stuff there at least as possible.

[@xn0gaming]

Ahh...Now I know where I saw your mannerisms before: Fran Blanche! You must be one and the same person.

[@cyphi474]

And so TRS-80 saga continues....

[@nbntelevision1]

15:41 Adrian proceeds to void another warranty. LOL

[@EngineeringVignettes]

The timestamp seems somewhat appropriate, considering it was a floppy drive getting the treatment.

[@stevedonkers9087]

If the Fujitsu chips are transceivers you should just be able to breadboard them (if you can find a datasheet) and see if you can make some LEDs light up through the chip.

[@series80]

I remember debugging an Intel 8086-based computer (not PC compatible) many years ago. I hooked a logic analyzer to the bus and could see the instructions being executed. Luckily I had the appropriate software for the LA so I could see the instructions as assembler mnemonics rather than hex codes. Anyway I realized the machine was stuck in a loop. Looking at the code I saw that it was waiting for the screen blank signal. So I checked that signal and while it appeared on the bus, it didn't show on the I/O chip pin. So with the machine powered up I connected the pin to the bus and I heard the disk drive head moving as the machine was trying to boot. Where I am getting at is that the repair may not be as complicated as it looks. You'll need an oscilloscope for sure and a logic analyzer would be a plus.

[@video99couk]

8:15 I had a bad mains filter capacitor on an Epson XP-55 printer. It blew the chopper transistor.

[@8BitRetroJournal]

I had a similar connector on a furnace circuit board that had solder joint issues...once re-flowed, our heat was back :-)

[@xredhead7135x]

For parallel capacitors, it is the sum of the ratings. Unlike parallel resistors (reciprocal of the sum of the reciprocals)

[@BlackEpyon]

My first concern would have been the RIFA, but that's already been replaced. Also, a note on the absence of a -5v, I don't recall any Tandy I've ever seen that had a -5v rail off the power supply, and not all of them even had it on the system bus either. At least the Tandy 1000 RSX, and probably the rest of the 1000 R series has a 7905 to provide -5v to the system bus, but so far as I know, none of the XT systems had it at all.

[@oddproductions]

That Grass soda reminds me of Meadow Tea, which I think is made by Swiss. Found it in Pennsylvania.

[@TatsuZZmage]

Only bright green soda I ever want is green river, God it's been ages

[@Video_Crow]

Every time I visit family near Chicago, they stock up on Green River, and it's all I drink while I'm there. I wish it would get wider distribution.

[@BrainSlugs83]

This is so damn nostalgic for me. I learned BASIC on a Model 4. (If you held down the little red button at boot it would boot into BASIC from ROM). If the issue is the disk drive board, I wonder if removing it and trying to boot to ROM would be possible. (I know the model 3 could do it, but don't know about the model 2.) Speaking of nostalgia, I love the modular design of those early Z80 computers with the backplane and cards like that, there was a project I found in the 2000s where someone had documented building their own Z80 PC like that, writing and burning a custom BIOS, and running CP/M and DOS on it. Though, I bet the design might make it hard to repair without replacement cards to swap in. If you want to use your logic analyzer on a card while it's running, I wonder if you can get a card edge extension cable, so that you can have the card flat on your bench while you probe it. If the custom chips are bad maybe you could do a collab with a hardware designer on youtube and get a replacement board made. I also wonder if the fan noise would improve if you added some silicone grease in there to lubricate it. I think the sanding and spray paint to prevent corrosion is totally fine. Though if you ever do get it working, you should paint your signature and the date, so that when it's repaired again in 50 years, there will be a history to the piece. Love your content Adrian, you rock!

[@shawbros]

It's the "Donut Panic!" shirt from WOOT!

[@DerekWitt]

Least it passed the smoke test. :) There was no earth-shattering kaboom. ;)

[@Geforcefly]

I use a remote controlled outlet for old devices I get in unknown condition, so that I can power them on and off from a distance with risking getting shocked (or worse).

[@Charlesb88]

A cheap substitute for a remote controlled outlet in this case that serves the same purpose is to plug a switched power strip into an Three prong extension cord then plug the device into the strip using a second extension cord. This allows you to switch off the power strip, switch on the device, then stand back and switch on the power strip and if needed quickly switch it off. As a temporary setup the use of multiple extension cords isn't a serious safety concern since it better then something blowing up it catching fire with you heads and/or face nearby. Note that this only works with devices with simple on/off switched not momentary pier buttons like modern desktop computers.

[@station240]

I've seen Astec PSUs in other microcomputers with those orange capacitors. They can leak in an odd way, the electrolyte melts the rubber boot and glues the capacitor to the board. Looks fine from the outside, only when you remove one do you find the failure.

[@8_Bit]

An 8" floppy disk has the power to make an adult look the size of a hobbit. It even works if the disk is offscreen; I saw Elijah Wood demonstrate it in a bonus feature on my The Fellowship of the Ring DVD.