IBM PC 5150 Rev. A S/N: 0126215

[compaqportableplus]

Wow, the original single sided drives was an absolute PAIN IN THE ASS to rebuild! But we got it. It fought me tooth and nail every step of the way.

Here it is after successfully booting PS-DOS 2.1 from a single-sided formatted floppy!



First, the latch mechanism was broken (common on early Tandons). I had a slightly broken TM-100-2A and was able to scavenge the needed parts from that.

Next issue was the stepper motor was almost completely seized, so completely tore the drive and motor apart to re-lubricate it. That obviously misaligned the heads, so I hooked it to my IBM XT and used ImageDisk to realign it.

BUT, at first I was not able to get it aligned at all. It turns out it was a combination of the pressure pad over the head being loose, the track-0 sensor being misadjusted, AND the stepper motor was misaligned as well. With all of that out of wack, it was impossible to align the drive with the adjustment screw alone. I was just about to throw in the towel, but I’m so glad I didn’t.

This success gives me confidence to finally tear apart the original DS drive in my other Rev A 5150, because the stepper motor is VERY stiff on that one, yet somehow the drive still works most of the time (though it sounds awful).

So there you have it, an original single-sided Tandon saved! This drive was manufactured in late 1981 as far as I can tell. I will set it up as the A: drive in this PC, and I will install a DS drive as B: for running programs.

 

[compaqportableplus]

PS-DOS 2.1

*PC-DOS I mean! I typed that post on my iPhone, so please forgive the typo.

 

[compaqportableplus]

Made lots more progress on the PC!

Just about done now aside from doing some rust removal and paint work on the top cover.


The original single-sided drive is working great. And I installed a spare double-sided Tandon I had. It has an IBM part number, but it doesn’t have the logo, so it’s fitting for this Rev A system.

I got the 64KB-256KB memory expansion card it came with working after replacing one bad RAM chip. So now between that, the 64KB memory expansion and the 64KB on the board, it has 384KB total. Very good for a floppy-only machine.

Now here’s something that has me stumped. You see, I thought this machine had been upgraded to the 10/27/82 BIOS, but that’s not actually the version it has.



The BIOS date is 08/16/82! There is an IBM XT BIOS version with that date, but I could not find a single record of a 5150 BIOS dated 08/16/82.

I also took a closer look at the chip, and realized the part number does not match any of the known three 5150 BIOS versions!


The part number is 5000024. And it’s dated 1982. I have never seen another 5150 BIOS chip with a 1982 copyright printed on it. The first two versions are copyrighted 1981, and the final version is copyrighted 1983.

So what’s up with this? Have I stumbled upon something extremely rare here?

 

[modem7]

The BIOS date is 08/16/82! There is an IBM XT BIOS version with that date, but I could not find a single record of a 5150 BIOS dated 08/16/82.

I also took a closer look at the chip, and realized the part number does not match any of the known three 5150 BIOS versions!The part number is 5000024. And it’s dated 1982. I have never seen another 5150 BIOS chip with a 1982 copyright printed on it. The first two versions are copyrighted 1981, and the final version is copyrighted 1983.

So what’s up with this? Have I stumbled upon something extremely rare here?

I added my comments to the dedicated thread that you created about this ROM.

 

[compaqportableplus]

Wow, I thought it was fixed, but the original MDA card started flaking out again and I could NOT figure out what was wrong with it. Pushing on the card with the machine on would make the screen flicker and if there was a bad solder joint, so I ended up resoldering EVERYTHING on the card, which still didn’t fix it! Was still cutting out and half of the time I would get no video at all.

So as a last-ditch effort, I put a ton of flux on the legs of the main controller chip and reflowed it with my heat gun! I figured that would either completely ruin it or fix it, and it actually fixed it! No idea why resoldering with my iron didn’t fix it but the heat gun did, but I’m happy. The card has worked fine ever since and pushing on the card does not make it cut out like it previously did.

Here’s a pic of the card and of it working after the heat gun treatment.





The way the chassis was dented on the front was actually “squishing” the MDA card into a bent position, so that’s probably what caused the bad connection overtime. It was extremely hard to get the card out on the first disassembly too. Now the case is straightened out and the card can sit in the slot without being flexed so hopefully it won’t have that issue again.

So, functionally, it’s pretty much set now I think. Quite a lot of work was needed, but it’s so worth it to have another working Rev A! I just love these early 5150s. This probably won’t be my last one either…

Next thing to do is to try and get that top cover looking a bit nicer!

 

[compaqportableplus]

Picked up an expansion card for this PC, it’s an original IBM serial card! It’s the early version with the wider, black slot cover and no jumper for the XT slot 8.





This is great to have since this PC didn’t have a serial port. I haven’t plugged anything into it yet, but I ran a system checkout utility and it does see the serial port, so I’m pretty confident it’s working.

I still haven’t done any work on the top cover. Are there any off-the-shelf spray paints that are close? Most stuff I’m seeing is too warm or too cold. I really want the color to be as close as possible.

Pantone 413 is the exact shade IBM used I believe. I would love to have some matched spray paint made, but I’ll have to look into that and see if there’s any place that can do it for an even remotely reasonable price.

 

[modem7]

Picked up an expansion card for this PC, it’s an original IBM serial card! It’s the early version with the wider, black slot cover and no jumper for the XT slot 8.

And, no U15 shunt block. Before U15, there was J9 and J10, and that is the card you have.

The circuit diagram for your early version is in the AUG81 edition of the IBM 5150 Technical Reference.

 

[Andrettigto]

How is the case cover restoration coming along? With that odd semi flat colour on that textured surface, it will be a challenge.

 

[compaqportableplus]

How is the case cover restoration coming along? With that odd semi flat colour on that textured surface, it will be a challenge.

I actually haven't gotten to it yet! The machine is pretty much done otherwise though, so what will be the last step. Now that it's a little warmer here I hope to get to it fairly soon. I don't plan on trying to replicate the textured finish exactly, as that would be impossible with the tools I have. I just want the color to at least be fairly close (which it should be with the paint I found).

I will definitely post updates when I start working on it!

 

[sniderman]

If you haven't already completed the paint restoration, figured I would share what I did. I had an old 5150 case that was empty and rusty so decided to build out one with a modern ATX mobo and GPU. The case had a large hole cut in it for a SATA HD reader so I needed to weld in a patch panel and refinish the case. After welding in the patch, I added body filler to fill in the small imperfections, sanded down the entire case, and then primed everything. In order to get the texture, I used Rust-Oleum Stops Rust Black Textured Spray Paint - 12 oz. I already had the black color from when I painted my 3d printed drive facia but would suggest you get the white or sandstone color since it will be easier to cover with your final paint coat. For the color, I wanted to get something off the shelf as well and found Rust-Oleum Universal All-Purpose Matte Farmhouse Greige Spray Paint - 12 oz. The final color was close to my old case albeit, a bit more grey than I would've liked. I've attached pictures of what the case looked like before and then after the build. Hopefully this helps.

Original case with hole in it.


Case after patching and painting. Note the texture and sheen.


Completed computer. Looks more grey here since I have it under a cool LED light.

 

[Andrettigto]

Sniderman, considering what you started with, it came out pretty good. Looks like you're ready to delve into a classic car restoration as I can't see any sign of the patch panel work.

 

[sniderman]

@Andrettigto Ha! I don't have the patients for auto body work but thanks for the complement. I was just hoping to show others a way to achieve a factory like finish with affordable off the shelf paint products.

 

[compaqportableplus]

A LOT has changed with this PC since the last post! And no, I still have not repainted the cover because I'm lazy

But, some of you know I found an even older 5150 in the original box that had been upgraded somewhat, so I borrowed a lot of parts from this one to get it back to original. This left me with the base machine to build back up however I wanted!

So much has changed but you can tell by the rust spot it's still the same PC! Still running the 16/64KB board too!



I finally managed to find a pair of those amazing black Teac 360k drives! These are not the Teac-looking Tecmate drives that came in the boxed 5150! I actually got these from a Rev B 5150 I just got, which there will be another thread about on here soon as well! This PC was kind of an unexpected eBay find and it was a great deal. I got the PC for less than people usually ask for these drives alone!

These have always been my favorite aftermarket drives for an IBM. They look and fit so good they could easily be factory equipment! After many years of wanting some I now finally have a 5150 with a pair of them installed and that makes me very happy! Both drives work great. That big red LED looks so cool on these drives!

I have also installed a 200w PSU, AST SixPakPlus (with 576KB plus the 64KB onboard for full 640KB) and a Western Digital RLL controller for the Miniscribe 3438 32MB RLL hard drive I installed! Not sure If this is the drive I will leave in here or not but I figured I use it in there for a while at least. Love the Miniscribe drives! That Miniscribe drive I got back in 2021 and the power supply and SixPakPlus card came from the other (boxed) early 5150 I recently got.

I'm actually still running the IBM MDA card as well! So no graphics yet but I will likely cave in and put a Hercules card in here or something. That MDA card is the one I repaired with the heat gun by the way, still working!

Oh, and I swapped out the BIOS for the 10/27/82 version, because that boxed early 5150 had been upgraded to it, so I swapped that chip into here and put that rare 08/16/82 ceramic/gold chip into the other one.

So that's where this PC is at now! Really, really happy with it I must say. I've kind of always wanted to build a tricked-out Rev A 5150 and now I have finally done it!

 

[compaqportableplus]

Another big change for this PC! I actually found a much nicer case for it on eBay! And yes it's a proper Rev A case with the DB-25 cutout (I wouldn't have settled for anything less!). The serial is a bit higher, 0145160, but that's good with me as it's exactly the same otherwise. It's not like this is a super early metal speaker bracket machine anyway.

Here's the after I moved everything into it! No more rust! Oh, and it still has all four cork feet! They were all missing on the old case.




It already had a parallel port from an AST SixPakPlus still installed in the DB-25 hole at the back, so I just left that there and connected it to the SixPakPlus I have in this machine.

And this case also had this really cool sticker from ComputerLand still attached to the bottom!



It was purchased on July 2nd, 1982 and had a 90 day warranty. Very cool!

Very glad I found this case! This was definitely an unexpected find for sure.