Leading Edge Model D Repair

[@nicejungle]

I became addicted to this channel. I have almost no interest about old hardware but this kind of investigation is better that any crime series on TV

[@DavidLightman]

Same here, also addicted to his channel, but i do like hardware, sometimes when he doesn't upload anything i go 4 -5 years and start watching old content again xD

[@subtledemisefox]

I watch these when going to sleep. I dream about the computer repairs while the video plays lol

[@esra_erimez]

Well stated, I couldn't have said it better myself.

[@mc_cpu]

I agree. Also like South Maine Auto for similar diagnostics, just cars instead.

[@mar4kl]

Great minds think alike, nicejungle!

[@seanys]

Feel better soon, Adrian.

[@granitepenguin]

Another great example of thinking through troubleshooting steps to isolate issues. A rare and valuable skill.

[@LonnonFoster]

So many feels watching this. The Model D was my parents' first PC, and it's what I spent countless hours on as a teen. This machine is what I used to learn BASIC, to play King's Quest and Starflight, and to make spreadsheets in Lotus 1-2-3 for building vehicles in Car Wars. Watching that boot screen come up made me smile so much. I'm gobsmacked at just how uncomplicated most of the ICs are on the board. "Just swap out the bad shift register chip" isn't something you hear much in modern computer repair, if at all. Watching you work through this repair taught me a whole lot about 80s-era text and video handling. I just got into electronics over the past year, and this kind of end-to-end problem solving is incredibly useful to me to see what I'm learning put into context. It's one thing to know what components do, but another thing entirely to see how they work together to solve complicated problems. Thanks for a fantastic video!

[@adriansdigitalbasement]

Indeed -- when I talked to people about the future of repair, I just don't see it being that easy. Ignoring the skill difference with SMD soldering, finding the bespoke parts that all these computer are made with now will be the trick in the future. There were perhaps only a couple bespoke parts on this entire Model D -- everything was off the shelf and easy to source. On something like a Commodore 64, tens of millions of the exact same machine was made, so finding replacement custom ICs is not that hard ..... but imagine some specific model of modern laptop, it probably contains a bunch of chips only used on that model or just a few other models.... then a year later a new models comes out and the chips are changed.

[@stephenhill4492]

Great video as always. As an asthmatic, I’d regard getting winded after three flights of steps as one of my better days, but I hope your own health improves, and you’re able to get back to normal quickly.

[@tomtomt1]

Take care!

[@adriansdigitalbasement]

Thank you I'm now nearly back to normal! I'm relieved!

[@BargainBarons]

Been LOVING your videos for close to a year now!!! Your level of knowledge is astounding!!!! My first computer was a Vic 20 then an IBM 286 with CGA (wouldn't be able to tell you more than that about it) and then in '88 I finally bought my own - a used Tandy-1000 with EGA when I was 12! HUGE upgrade for my PC gaming at the time!! 😄 Small Canadian channel and a fan!

[@danman32]

When you pointed out the data lines between the character ROM and P2S chip, I immediately thought of taking the ROM out and manually driving the lines high/low.

[@mandrakethemadcoder]

Love how you go into detail and show your exact process. ❤

[@kyorin6526]

I like the simpler videos as much as the complex ones. In fact, I learn more from the simpler ones sometimes as I'm able to understand better what's going on.

[@marcinkowalczyk647]

Hope You are 100% well soon Adrian ! Good video as usual, can't wait for followup with the Plexus

[@matthewspence3251]

It freakin’ works ! Surely time to invent the adlib dance party. Highways.

[@adriansdigitalbasement]

Heh! I bet someone could port the DK Country theme to work on the Adlib for me!

[@tom23rd]

Holy crap, that was my first PC, when i convinced my dad we needed better than the ti99/4a. Mine was a later model d, 10mhz, 3.5" 720k and 30mb "ide" drive that would make my later 386 not even boot when i plugged in. Oh, and vga. Sorry about the covid dude, i had it twice last month - big same on the short of breath, take heart, my capacity has come back.

[@herrbonk3635]

Twice? Wow! How did you know? In my country, Covid Sars2 is not even talked about anymore. And since 2022, people are (almost) never tested. Not sure why, but that's how it is.

[@tom23rd]

@@herrbonk3635 at home PCR testing

[@Starchface]

I enjoyed this diagnostic and repair process, even if you made it appear trivial, a fine illustration of deductive reasoning and of your deep understanding of the inner workings of these IBM clones. The Zoyi is proving its worth on these vintage machines where the bandwidth limitations are not so much a factor. It certainly beats a logic probe. I have been watching your videos since the Adrian Black days-long enough to know that you often consider appearance to be secondary-but I think a dose of peroxide would do wonders for the front panel, or paint for that matter. It's very satisfying to see not only a functional restoration but a cosmetic one. Maybe I just don't like yellow! I don't know if you realize it but it is clear you are an inspiration to many retro-computing enthusiasts on this platform. Thanks for yet another superb video.

[@supralapsarian]

Sweet! What a classic beige box. These things were everywhere back in the day. Great job bringing the old girl back around!

[@udasai]

What a blast from the past. I used this computer (with dual floppies, 640K, Hercules graphics and later CGA) from '83 to '89. One of the earliest PC clones, half the price of a real IBM.

[@garthhowe297]

These troubleshooting episodes are why this is my favourite channel.Great going Adrian!

[@borgquads4669]

This was my first PC. I bought it used when I was 12 and put a 40 MB HDD card in it, ang got a 1200 baud modem. Browsing the internet via shell service. I learned so much from that computer.

[@mistermac56]

At the college I retired from as an engineer in computer services, we had hundreds of the model M (Mitsubishi) Leading Edge XT clones. They were extremely reliable and we used them until we moved to the 486 Compaq.

[@horusfalcon]

Nicely done! A little forensics on the board verified it was similar enough to an IBM CGA to be treated like one. The rest was poke-n-peek troubleshooting - inject a signal and see what it looks like. Marvelous.

[@maqthedon8969]

Absolutely love the troubleshooting steps you're showing, it's a skill unfortunately mostly lost to time, with the throw-away culture we have today. Love the channel, brings back the memories of the good ole' days, playing with these retro machines when they were still hot off the shelves!

[@notneb82]

The blue logo is simply that no one ever peeled the protective plastic off. Peel it off, it looks much better without it.

[@adriansdigitalbasement]

Funny. I also say evidence of other areas like on the rear badge where the protective plastic hadn’t been peeled off. It was all degraded now which makes removal super hard.

[@adriansdigitalbasement]

And yes that was it, it’s the white label underneath! Too funny!!

[@stevethepocket]

Huh. I guess in those days companies wanted to make sure you knew the plastic was still on, so they tinted it. Clearly it didn't help.

[@TheErador]

​@@stevethepocketI think it's more that they removed the dye as a cost saving exercise at some point

[@jbinary82]

I found funny to find lot of people to not have peeled rims logo in lot of cars from streets😂

[@ggmg7178]

I love that you explained the thought process behind the repair here. It really helps me learn how to troubleshoot these kinds of things myself.

[@ukmk3supra]

I really enjoy the diagnostics videos you do, everything is so well explained and it's just easy to follow - hope you feel better soon!

[@CharlesBundy-z9n]

Best wishes for speedy healing. ❤

[@johngangemi1361]

I like your troubleshooting skills and the resistor trick with the shift register. I am learning something new everytime I watch one of your videos. Keep it up Adrian! (I only discovered the channels recently).

[@kreeger2010]

Terrific channel. Happy to see an old machine restored to working order.

[@TheBitPunch]

The Leading Edge Model D was my family’s first IBM compatible home computer (vic20 before), and even though it was old when our neighbor gave it to us in 1996, they were gracious enough to provide all of the manuals, system software, and many games. It was a treasure hunt after I read through the manual in an afternoon and began searching the 20mb hard drive. All kinds of cool stuff on there. ❤❤ Memories.

[@DavidLightman]

I love your analisis of the problem even before starting to probe the board, you really have a very good understanding of how everything works, this is GOLD! thank you.

[@dhpbear2]

Ahh, back in the day, we referred to these as "Trailing Edge" :) We had one dedicated to burning PROMs

[@kd5byb]

"Trailing Edge" = 🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣

[@williamsquires3070]

Yeah, all the ones I ever saw were total POS (and I don’t mean, “Point Of Sale,” either!) 😂

[@jbloodwo]

@@kd5bybleaking edge. And they also had a crummy word processor.

[@marcokrijgsman8099]

This was yet another example of craftsmanship in problem solving in the computer field. I love watching your videos. Yes, I know that Covid is spreading around the world somewhat in a milder variant. And the fact that you have just now been infected with this is bad. I wish you well. That you will Get Better Soon.

[@jandjrandr]

I like the fact that you solve this one without using an oscilloscope. The visual evidence with progressive testing gives away the likely candidate very quickly.

[@zap2002]

Man, I learn so much from your videos. You should be gifted an educational grant or something lol. Keep it up Adrian, also, it's such a joy to meet and greet you at the VCFs.

[@radio-ged4626]

Nice straight forward logical fault. Great repair - wishing you a speedy recovery.

[@weepingscorpion8739]

Oh, Adrian, you have nothing to apologise for. As cool as the complex videos like the Plexus are, I and certainly others too also love these "simple" fix videos. So, just keep them coming too :)

[@ferrari2k]

Hi Adrian, I rarely comment but I love your "think first, poke around later" approach that leaves these machines with minimal changes. Really cool! Keep up the good work and I hope you get better soon, but from all I know about Covid, that might take some time (weeks or months...) and you absolutely should not exhaust yourself or you risk damaging your heart.

[@baronvonschnellenstein2811]

All good, Adrian! Nice to mix up the complexity and target platform - You get to fully clear a backlog item in the process :) Wishing you Godspeed on your recovery - these ailments can take a fair chunk out of us, eh?!

[@dionelr]

Love your thought process on this one. I could actually almost follow along! I hope you get back to 100% soon.

[@policyprogrammer]

I had a D2 and D3, the 286 and 386 machines. We liked Leading Edge. They were great machines and inexpensive.

[@WilliamLeue]

Feel better quickly, Adrian! The respiratory effects tend to last for several weeks after you start testing negative. Take it easy!

[@Trevorodunne]

Great Video Adrian I was nearly sure it was the video ram on the card great work.

[@ntsecrets]

My dad was a leading edge dealer. I know they once had a problem where the zener diode that charged the cmos battery was installed backwards so he had to hand solder those to fix.

[@fesaopilger]

Adrian, you are doing an awesome work by repairing computers. I'm hopping you get betterr from covid as soon as possible

[@jdebultra]

I hope you get better. I got COVID right when it came out. My lungs never recovered but I was a smoker. Nice repair, looks great on that monitor.

[@MikesArcadeMonitorRepair]

Fantastic troubleshooting as always. Great job.

[@johnwells558]

Always look forward to your videos. John, UK

[@mar4kl]

My first job was programming financial software in BASIC back in 1987 (yeah, I had no idea anybody did that professionally until I was offered the job!), and the company had a veritable revolving door of IBM and popular clone PCs largely to ensure that our software ran whatever computers the customers had, which was anything but guaranteed back then. At some point, we got a couple of those Leading Edge Model Ds, and one of them became my programming/testing/support PC for a month or two. It wasn't my favorite PC, but it wasn't half bad, either.

[@antonglushkov2327]

Желаю тебе восстановления без последствий! Ты создаешь годный контент, мужик!

[@xianox8]

This was a very good video! Good length also! Adrian, King of infotainment!

[@timb7085]

Excellent video - as always... I keep learning new troubleshooting tidbits! thanks!

[@paco3447]

still own my late 93 Leading Edge full spec 486DX2 66 Tower (a very rare version by the way) buried in some box altogether with my Amigas, Ataris, speccy, etc. somewhere in my garage. I loved that machine by a lot back in the day. Internally everything was labeled as either Daewoo / Goldstar as long as I remember. The tower case was rock solid built.

[@donkeymedic]

I found his outro funny. He said "i'm not ready for anything super complicated". I know electrical engineers that would have a hard time explaining what he just accomplished in this video. It's amazing how far you have come over the years. I look forward to your videos some much, that I missed them and was worried about you. Glad to hear you are recovering. I am a paramedic, and will say COVID is a unique virus. Most virus affect upper respiratory more. It's the drainage that inflames the bronchioles and causes chest congestion with wheezing. Covid however affects the cells and mechanisms that are responsible for gas exchange. I could get really technical about this, but that not important. A lot of COVID patients will have little to no wheezing, but will still have low oxygen levels. It may take 2-3 weeks to recover fully, but has long has your resting O2 levels are greater than 90%, you should be ok. Wish you speedy recovery.

[@g4z-kb7ct]

If you know electrical engineers that don't understand basic concept of data lines being pulled high/low to give a 0 or 1 (which is actually what happens anyway, but is CPU-controlled) then they are not real electrical engineers.

[@donkeymedic]

@@g4z-kb7ctMy comment is in the way he explained it. I am attempting to describe a subjective view not an objective fact. I am not sure why this warrants this response. Your response proves my view. You gave a very technical response, that you and I may understand, but the average person does not. Great your are smart, but can not give an entertaining response to a complicated engineering concept; that also helps someone understand the concept. My purpose of the comment is to complement the content provider.

[@g4z-kb7ct]

@@donkeymedic ok I see. well if that was your purpose, you failed lol

[@donkeymedic]

@@g4z-kb7ct did I lol😜

[@g4z-kb7ct]

@@donkeymedic You got that mixed up but that's understandable given the level of your comments. The 'I' should be first.

[@FortyTwoAnswerToEverything]

This was my first computer ever. My dad bought it for a few thousand dollars (including CGA monitor and dot matrix printer). Didn't have a hard drive but I still learned so much from that machine with the supplied DOS disks and a few programs. Learned how to create .bat files with that thing. I was about 10 years old.

[@Yrouel86]

@4:50 my goto is to replace the NiCd batteries with a CR2032 holder and use a CR2032 and disable the charging circuit on the motherboard by lifting a leg of the resistor or diode that brings 5V to the battery (the basic circuit is 5V -> D -> R -> B+ where D and R can be swapped). This way the modification stays pretty neat and completely reversible

[@lanefu]

the debugging method on this episode is one of my favorites!

[@ultrametric9317]

Good work. Very instructive. Feel better.

[@TheTopace88]

Great Video! Really fun to watch. I also find it incredibly relaxing. Why didn't you check the connectivity of the traces/data lines between the character generator and the parallel to serial chip register first? This is not criticism, just a curiosity as my knowledge is only what I learn from watching.

[@MikesTek]

Love to see another leading edge video. You talked about the extra memory in your other video on it having 640x200 16 colors. Special place for these as this wamamy first pc clone. One day i will find one that isnt 300 on ebay and relive that childhood memory. Maybe even max it out and live a dream never fulfilled

[@Dinnye01]

Had covid a year ago with pneumonia. It took me 4 months to regain my full lung capacity and thebafter effects are with me since a year. Take care, it heals very slowly.

[@scottlarson1548]

The same thing happened to my Ohio Scientific C1P video forty years ago: one of the input lines of the 74166 died. I had to write something for school on it with one vertical line missing which was annoying. I had no confidence in my desoldering skills so I simply clipped pin 16 and piggybacked a new 74166 on top of the old one.

[@adriansdigitalbasement]

Awesome! Yeah that’s the best way to get a chip out if you don’t want to risk any damage. And yes, the 166 is probably used in most display circuits from the early 80s and late 70s. So this would be a pretty recognizable fault!

[@petesapwell]

@@adriansdigitalbasementThey’ve been in video since the first video game…They’re to be found on TAITOs Space Invaders PCB doing exactly the same job.

[@frugalprepper]

Awesome Vid! I love these repair videos!

[@EdwinNoorlander]

Get well Adrian. Take your time.

[@hugoegon8148]

Great analyzed and very understandible explained, I love your repair videos. 😊

[@BargainBarons]

BTW... we make garage sale VLOGS and visit a couple dozen or more garage sales every week... if there's anything in particular you have been looking for I can always keep an eye out for you, plus it would be a fun collab! Cheers from Canada! 😀👍

[@user-nd8zh3ir7v]

what a great explanation of the character roms, thanks

[@GuiOpsDev]

Good Lord. You brought me out of KZbin commentary retirement. ONLY because I worked for a Leading Edge dealer and this was our bread and butter, So, the blue color of the badge is because the original protector is still engaged. As in, "peel the sticker off, moron!" If you can't peel it off, the original owner was a moron. You are now stuck with it. The IBM XT and AT had the same basic chasis. The LE Model D had a squat, square chasis and sported BOTH colour and mono support. However, some people wanted the same footprint as an IBM XT or AT, so the Model M was created. Back in the day, NOTHING was integrated into the main logic board, so expansion cards were the answer. The Model D only had four slots, while the Model M sported something like 6 or eight slots. There was also a "turbo" model of the Model D released, as I remember. This was for those pieces of software that didn't check for timing (how fast one second on the system clock equated to clock cycles) and ran too fast. Funny how we take things like "processor clock cycles" for granted in this modern, multi-threaded world. How robust were these machines? Well, a storm had several lightning strikes in a very small village of northwest Ohio. I had the service contract and arrived immediately after the storm. The call was because their electric billing computer wouldn't power on. A clear case of power surge, file an insurance claim. I knew the PC was dead, but I went through the motions. I opened the case and saw what I can only describe as "an inverted pyramid in the center of the BIOS chip". I could literally see the traces from the center of the chip to...wherever the ended up at on the prongs ( I presume... ) Now, it was 1986 and as long as I parked the heads on any hard drive, I could transport it. Being so, I traveled with my service PC for on-site jobs. It was a Model D, non-turbo. Just for kicks, I swapped my BIOS for the blown up one...and the b**ch fired right up!! I SHIT YOU NOT!!! Too bad they went out of business...

[@uomoartificiale]

Adrian: sorry my brain cannot think through complex stuff yet... and then proceeds to find the faulty bits on the data lines with a resistor and another computer's schematics 😂 Great work as always Adrian. Take your time, get well soon

[@paulkeenanmusic]

That opening theme gets me everytime! love it.

[@TheDefpom]

Nice diagnostic work.

[@SonjaWeygand]

Very enjoyable video thanks, love these indepth fixes!

[@DavidRavenMoon]

The Leading Edge Model D was designed by Stephen Kahng, who later founded Macintosh clone maker PowerComputing. I had a PowerComputing PowerCenter 132.

[@samshort365]

I still have mine. Couldn't get rid of it.

[@johndoe4314]

Love these repairs Adrian! Thank you

[@SobieRobie]

Good job sir!

[@MadManDarkJedi]

Adrian's T Shirt got my attention. It's so cool.

[@tony359]

When I got my Apple //e it had the same exact issue and it was the same 166 chip!

[@Colin_Ames]

Great video, as always.

[@mike44njdevils1]

Hey Adrian, I had COVID in March. I'm a trained vocalist and do shows on the local level. I normally can move around on stage, even light dancing, while singing with no issues. Now, I can barely move faster than a quick walk else in completely winded. I can't stand this.

[@SuperHaunts]

Excellent video - sending some info for your reference

[@BrassicGamer]

Super satisfying!

[@smarthome2660]

First question to ask all customers is "did you let the smoke out? Hard to believe that PC sold for $1,495.00 back then & included 20 MB hard disk, 8088 CPU supporting speeds up to 7.16MHz, and 640K RAM

[@peregrine1970]

Shorter video, yes. Still a really excellent video Adrian!

[@trevorward85043]

Another very educational video!

[@JimLeonard]

Fantastic overview of the CGA schematic! As a software guy, for faster diagnosis, I was going to recommend instead of a DIR to fill with characters, try ALT-219 a few times to print some solid blocks onscreen. But you, as a hardware guy, correctly figured out removing the chip and causing floating values would do the same thing :-D Nice.

[@terryraymond7984]

Good to see Rami

[@spuwho]

The Model D was a big deal because it was the first clone that could pass IBM XT Diagnostics without an error back in 1988. After it was reported sales went through the roof. Up to that time many XT clones had compatibilty issues.

[@randomblogger2835]

74LSxx is TTL so it will have internal pull-ups on the inputs.

[@twocvbloke]

Logical thinking and investigating helps with diagnosing problems, often taking less time than throwing parts at stuff hoping to find a fault... :) (Kind of like how the local powergrid people here were throwing fuses at the local substation thursday and friday to deal with repeated powercuts hoping that fixed the problem, until they actually found they had a bad underground cable when the smart engineers came in to think logically and find the fault!!!)

[@timc3600]

Nice work You could also test the faulty IC in your TL866/T48/T56 and prove the same two outputs are faulty.

[@shorty1k]

My first pc was a leading edge. I get nostalgic every time I see that logo

[@FordGT40MkIV]

Did you notice if there was a short to ground on any of the ‘166 data pins before removing it? Sometimes the problem may be even simpler than a bad chip.

[@Mulletsrokkify]

Get well soon Adrian

[@larryk731]

I remember in about 1986ish a friend of mine had this exact model of machine. At the time I had a noname XT clone with slightly better specifications.

[@jaybird57]

Good job man! Good job!

[@VShuricK]

27:30 Adrian, you owned TL866. And this thing can test almost all 74xx chips, 74166 included. I test all my spare IC and throw away a few dead, unsoldered from some boards.

[@D3M3NT3Dstrang3r]

Don't usually care too much for graphics on shirts but I like that one..

[@geoffcollins6601]

Fantastic video thank you

[@FennecTECH]

As someone who’s seen the effects of covid first hand im not surprised its got you worn out. That shit tears your lungs to shreds. Just take it easy and tinker with some lighter weight machines and pray you dont wind up with long covid

[@starsundsternchen802]

Super nice video!

[@rivimey]

Fun video Adrian, thanks. Did you notice there are actually 4 of the ls166 chips beside that chargen eprom? I was trying to understand why it would need four of them!

[@slightlyevolved]

Adrian: Winded after three flights of stairs while recovering from covid. Me: Winded going up four steps to my front door.....

[@MattyEngland]

Me: Had half my lung removed 7years ago, never vaccinated, never wore a mask, never got covid despite working through both lockdowns meeting hundreds of people per day. Still walk miles without issues.... Stop taking the vaccines ffs