IBM PC 5150 Rev. A S/N: 0126215

[compaqportableplus]

Found myself another early IBM PC! This one’s even older than the last one, though it needs a LOT more work. Lots of dirt and rust to tend to.

Here’s some pics of it in the condition I received it. I will be stripped and carefully cleaning and testing each part one by one.









It has a stamp of November 19th, 1981 on the inside of the front, though I see 1982 date codes on some of the motherboard chips, so maybe the board was replaced, or maybe that date is just when the case itself was made, but either way it is still a 16KB-64KB board, so I don’t really care. Really happy to see the ‘78 copyrighted 8088 still present too.

And it does have the bronze power supply with non-recessed nuts. Hard to tell with all that dirt on it, but it’s definitely has that brownish shine to it. Very cool.

And it does still have one of the original single-sided drives present too, which is really neat I think.

It has three original cards with the black back plates, an MDA card, floppy controller and 64KB memory expansion. It also has a later 256KB IBM memory expansion with the silver back plate.

Super excited to restore this PC. I will add more details and pics as I make progress.

 

[compaqportableplus]

Okay, the power supply is NOT working unfortunately. It will come on for a spit second and then shut off like something's tripping it. I don't know what's up with it. Anyone else have this issue?

However, after replacing one shorted cap on the motherboard, it gives me the one long, two short beep code for video, so the motherboard is at least trying to work. Will have to throw in a display adapter and get a monitor hooked up.

 

[compaqportableplus]

We have life!



All of the 64KB of the board passes the self test and no bad ROMs! Very happy. The board has been upgraded to the 1982 BIOS.

The MDA card seems to be dead, but I’ll give the contacts a good cleaning and see if that helps. If it’s really dead finding another shouldn’t be terribly hard or expensive though.

Not sure what I’ll do about the power supply yet. I may just rebuild it internally with a more modern PSU until I can figure out what’s up with the original. I definitely won’t do any irreversible mods to the PSU case. FYI: I'm using a different power supply in the photo above to power the motherboard.

Either way, I’m extremely glad and relieved the motherboard works without issue!

 

[chris_nh]

Why rebuild the power supply? Sounds like it is working just fine.

 

[compaqportableplus]

Why rebuild the power supply? Sounds like it is working just fine.

Read my previous post. The original PSU isn't working. I'm using a different one in the pic.

 

[oldpcguy]

Read my previous post. The original PSU isn't working. I'm using a different one in the pic.

It wasn't clear as you stated it did not work and then followed that with a shorted capacitor replacement which then resulted in a functioning system. IOW it sounds as if the shorted capacitor was causing the power supply to shut down and, after fixing it, that was no longer the case.

Glad to see everything is working good for such an old system.

 

[compaqportableplus]

It wasn't clear as you stated it did not work and then followed that with a shorted capacitor replacement which then resulted in a functioning system. IOW it sounds as if the shorted capacitor was causing the power supply to shut down and, after fixing it, that was no longer the case.

Glad to see everything is working good for such an old system.

Apologies if there was any confusion caused by my post. No, the shorted cap on the motherboard was not the main cause of the PSU fault. The motherboard is being powered from a different PSU in the pic.

 

[Andrettigto]

Really nice find! With some needed restoration efforts it’ll be a treasure. That serial number is early so it must be one of the first to use the newer plastic speaker bracket. I see some sort of logo on the DS/DD drive faceplate. Doesn’t look like an IBM logo.
Shame about the top cover corrosion as “repaired” ones I’ve seen never seem to look right. That power supply is beautiful, wish my systems still retained them.
Your collection is amazing. Be sure to display them!

 

[compaqportableplus]

Really nice find! With some needed restoration efforts it’ll be a treasure. That serial number is early so it must be one of the first to use the newer plastic speaker bracket. I see some sort of logo on the DS/DD drive faceplate. Doesn’t look like an IBM logo.
Shame about the top cover corrosion as “repaired” ones I’ve seen never seem to look right. That power supply is beautiful, wish my systems still retained them.
Your collection is amazing. Be sure to display them!

Thanks! Yeah, I’m not sure exactly when the plastic speaker mount started, but this is definitely an earlier one I think.

That is an IBM logo on the double-sided drive faceplate. It’s a newer drive from 1984 that was obviously added later.

The rust is unfortunate, but I’ll see what I can do with it. That’ll come last though. I’m going to get the machine fully complete and working before any cosmetic repairs.

 

[compaqportableplus]

Found this date on the PSU fan, so looks like this is an early 1982 unit, which means the motherboard is probably original. Very cool.



I can’t for the life of me figure out what’s wrong with the original power supply. I removed and tested a lot of components and replaced some caps, none of which helped.

So I will definitely be rebuilding this power case supply with the internals of an AT or ATX PSU. I have a relatively new unused ATX power supply that has -5v, so that may get sacrificed for this restoration.

The original AC fan in the pic above works great and is extremely quiet, so I will definitely be reusing that.

 

[oldpcguy]

Thanks! Yeah, I’m not sure exactly when the plastic speaker mount started, but this is definitely an earlier one I think.

That is an IBM logo on the double-sided drive faceplate. It’s a newer drive from 1984 that was obviously added later.

The rust is unfortunate, but I’ll see what I can do with it. That’ll come last though. I’m going to get the machine fully complete and working before any cosmetic repairs.

I've used this product with great success: Iron Free

 

[compaqportableplus]

I've used this product with great success: Iron Free

Might have try that! Thanks for the tip!

 

[Andrettigto]

It’s neat that they run on 110v a/c, maybe that’s why they’re so quiet.

 

[VERAULT]

Rebuild it like i did to my early 5150 on another post. In fact I bought another of those new AT psus to rebuild my most recent 5170 dead psus also. Its just easier and morr reliable.

 

[compaqportableplus]

This turned out great! So, I have actually had the functional guts of a newer silver 63.5 watt 5150 power supply I gutted several years ago laying around collecting dust. I gutted the PSU and rebuilt it because I needed more wattage to use it in an XT (I wouldn’t have done that nowadays to a working stock PSU by the way).

I gave it a good cleaning, tested it and found it still works great and has strong and stable rails.

It turns out that the power supply board from the silver PSU is almost identical to the one in the bronze power supply and its bolts directly in with no mods!

So here is that PSU board installed in the original casing.



Now THAT makes me happy. It’s almost like nothing was ever changed. There is some small differences to this later PSU board, but nothing major. I’m really shocked the PSU was dead. Honestly the 63.5 watt PSUs have been very solid in my experience. Maybe the early ones had more issues? Who knows.

Oh and here’s another issue solved. For some reason the chassis had a big dent in the top of it at the front, which made insertion and removal of cards extremely difficult. Sat it on a hard, flat surface and pounded it flat with a hammer! Worked great.




Still has a slight ripple, but it looks much nicer and now cards should fit normally.

Oh, and here’s a pic of the motherboard for anyone interested.



It’s not just any PC board, it’s THE PC board!

More to come!

 

[compaqportableplus]

Motherboard and PSU reinstalled!



There is some rust on the bottom case, but I’m going to leave it for now since it isn’t really visible with the unit assembled. I’ll probably try and tend to it at some point, but I’m more concerned about the top case right now, as it’s considerably worse and more visible.

 

[VERAULT]

Thats pretty much what I did with my 5155. I had a spare 5160 psu soi put the guts in the unreliable 5155 psu chassis and it worked great.

 

[compaqportableplus]

Got the original MDA card working! Cleaned the contacts and reseated the character ROM. Very happy it’s now working!



I also got the early 64KB memory expansion card working. Replaced one shorted cap and at first was still getting a memory error, but I fiddled with the dip switches and it now works and counts up to 128KB without errors!


Didn’t have any 10uf tants left, so I just used an electrolytic for now.

 

[VERAULT]

I dont think its a good idea to replace tantlums witb electrolytics. Best to just order some replacements.

 

[compaqportableplus]

I dont think its a good idea to replace tantlums witb electrolytics. Best to just order some replacements.

Really doubt it will hurt anything honestly in this case. I put an electrolytic on an IBM XT board once as I didn't have a spare tantalum at the time, and I never even went back and changed it. Computer worked fine up until I sold it. I will be changing it with a tantalum eventually though, as it will look much nicer.