IBM PC 5150 repair: the motherboard lives!

Part 2 of the IBM PC 5150 motherboard repair, I continue troubleshooting and get it fully working.

Part 2: This part!

--- Video Links

My initial testing of this IBM PC 5150 motherboard:

Great resource for IBM PC information:

IBM PC 5150 Switch settings:

IBM PC 5150 Technical Manual: (64-256k)

RGB2HDMI: (What I'm using to capture CGA)

Adrian's Digital Basement Merch store:

Adrian's Digital Basement ][ (Second Channel)

Support the channel on Patreon:

-- Tools

Deoxit D5:

O-Ring Pick Set: (I use these to lift chips off boards)

Elenco Electronics LP-560 Logic Probe:

Hakko FR301 Desoldering Iron:

Rigol DS1054Z Four Channel Oscilloscope:

Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:

TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)

TS100 Soldering Iron:

EEVBlog 121GW Multimeter:

DSLogic Basic Logic Analyzer:

Magnetic Screw Holder:

Universal ZIP sockets: (clones, used on my ZIF-64 test machine)

RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)

Plato (Clone) Side Cutters: (order five)

Heat Sinks:

Little squeezy bottles: (available elsewhere too)

--- Links

My GitHub repository:

Commodore Computer Club / Vancouver, WA – Portland, OR – PDX Commodore Users Group

--- Instructional videos

My video on damage-free chip removal:

--- Music

Intro music and other tracks by:
Nathan Divino
@itsnathandivino

[adriansdigitalbasement]

The EPROM I used is the WS57C49C. It's drop in compatible with the 2364 in most cases but can't be programmed by many programers. I use the DataIO 2900 to program them.

[wildstoo]

I know someone says it in almost every video, but I'll say it again. I really appreciate that you leave your "screw ups" IN THE FINAL EDIT when you miss clues or fail to notice something, rather than hiding it in the edit or reshooting. It makes the whole thing feel much more cohesive and true to life. Thanks!

[TofersCarTales]

The genuine joy you express when it finally frikin works truly warms my retro heart. Thanks Adrian!

[jowi_seven]

Your surgery diagnostics are mesmerising. I wish brain surgery could translate in a similar fashion. Imagine people getting their lives back by replacing a part or resolder the connections.Thank you Adrian

[atkelar]

Speaking of CGA hacking... There was a "256 colors on CGA" listing in one of the old 1980s computer magazines. It did some low level reprogramming to give you a 160*100 or so 256 color mode. Worked fine, but was slow as it can be on an XT so I just looked at it, and never used it for anything. Besides, VGA was already a big new thing too, so nobody was getting new CGA cards back then. Wish I would have kept the code for reference though...

[ovalteen]

That 160x100x16 "fake graphics" mode is slightly documented in the technical reference manual. Few people used it because there was no direct BIOS support. You also had to watch the timing in order to prevent snow, like with all direct memory writes in text mode.

[MisterZealot]

Gotta love how giddy Adrian gets when a problem is solved. So wholesome. 😅

[NEEC]

Excellent. That parity error message only flashed on screen so very briefly. So easy to miss. But you got it.

[bryondillon]

Good job showing the mistakes that can be made while troubleshooting hardware. A lot of people would just cut this from the video, but I believe that it is valuable to show this kind of thing, because everyone should learn to double check their work, be patient, and take your time. Trying to hurry through with assumptions ends up in replacing components that do not need to be replaced. Keep up the good work!

[adriansdigitalbasement]

I had to reupload this video, so some comments from Patrons are gone. I'm sharing a few here:


@silvestronsbitsandbytes
Love love love seeing the logical deduction used in this repair, but it also helps when the docs are accurate! I'm troubleshooting my own 5150 right now with a solid high /CE on U33 lead me to a dead /MEMR line only to find the schematic linking it to a write line on U6 which didn't make sense at all. Thankfully, minuszerodegrees has a footnote explaining that the schematics are wrong, but I spent way too long going in the wrong direction when I should have trusted my instinct. Great job.


@JimLeonard
The CGA Compatibility Tester strikes again! But hey, you should upgrade to the latest version, added some more tests and color changes you requested.


@rdh2059
Adrian: Love watching your work. Here's a question for you. You repair a lot of computers. What do you do with all of them? The notion of fixing them to sell on eBay doesn't sit well with me. Very few young people are remotely interested in retro computers... So back to the question. What do you do with your repaired computers? After all, how many C-64s do you really need?!

[[My answer is I give the machines away to people in the local Portland area. I don't have time to pack/ship stuff, so the local folks benefit.]]

[GYTCommnts]

Ahh, my saturdays are not complete without a repair adventure! About the use of the tester and the dead parts case, I like that you included them at the end! I understand why not using the tester while troubleshooting, but it's nice to check later if the tester would have indicated a fail chip. Awesome episode, as always!

[christopherdecorte]

The cyrix cpu is such a beautiful chip you have it rein rezened and use as decorative art or paper weight. Some old chips have a unique beautiful factor to them.

[chumbawumba]

Mad props to you and those that can do board level repair down to caps, chips, etc. I am lucky to be able to replace a PRAM battery in an old Mac, LOL! I think my trepidation is nightmares from the early 80's when I was in rock bands and trying to custom build guitar pedals and other stuff like that. Burnt fingers and creating a mess of solder is all I could get done, most days. Good thing I gave that up and made my career as a Dec Vax guru and later in career a very proficient network engineer.

[Cherijo]

I really appreciate that you didn't name and shame the person who wasn't as experienced at soldering. It's far more important to put out the education on what you really need to do these repairs on certain machines than to shame people.

I have a pretty good idea of what video(s) you're talking about because I believe I attempted to watch that video or two as well, and I had to stop at that point for a minute because my brain cringed. I have a 5160 myself that I have been considering preemptively recapping as everything is all original in it currently. I knew the back planes in these things were super heavy and difficult to work with without the right tools, so as someone without a hot air workstation currently, I was already hesitant, and then I watched those repairs and I absolutely decided to put off this repair until I could get the right tools because I could see them struggling so much to do the repair properly. Sometimes the learning comes from watching others struggle, and that can be okay.

PS, I very much enjoy commenting at my screen occasionally when I see you miss something, and that's part of the fun for me! My kid just gets embarrassed and tells his other mom that Mom B was spouting off at the Portland Basement Nerd again. 😂😂 Please keep being you because it's absolutely enjoyable and fun to watch!

[jcspaziano]

I love watching your troubleshooting process. Ive been a Sys Admin / engineer for almost 30 years and your channel has so much valuable knowledge that far extends the entertainment factor. Congratulations on your channel’s success! Ive been here a while!🎉

[xianox]

I hope you take some time to take break this summer. Thanks for the cool content and best wishes from Sweden. /J

[ovalwingnut]

This show has all the elements of a good mystery, who dun-it and block buster action film. Good job!

[sarahblikre]

I can't get enough of these types of videos. I wasn't around in the 80s but it's fascinating to see the technology that was available and how to troubleshoot it.

[Wikcentral]

Another nail biter. 10/10 results. Your trouble shooting skills are more advanced than many so called professionals that I work with everyday. I run into this at work very often. When you are not 100% familiar with the operation of the machine or the software its super easy to take the long way around to understand what is happening and maybe slip up trying something just to prove fault. Realizing the mistake and understanding what you just saw is a skill many do not have. It is a skill that is underpaid and under appreciated. Thank you for sticking to it and sorting it out and posting such a quick update to this mystery. I once had an incredibly confusing service call when some fire extinguisher residue damaged a bank of dip switches. It made no sense to me why the software was being configured to completely different options not matching the dip switches. I finally removed the dip switch assembly and hard shorted the pins with solder bridges. Before that I had myself convinced that the rom was glitched and I was not going to solve that in the field. PS> I hate it when you bring out the retro chip tester, it reminds me I still have that pcb sitting in my bin of projects waiting for parts ordering and assembly. ;)

[KameraShy]

It looks like IBM did an excellent service to the community by providing such comprehensive documentation of the computer's internals and processing. Not trying to hide under some false guise to force customers to use their own repair facilities. Like others do now. Stand up for right to repair and thanks to Louis Rossmann.