5150 rebuild project

[bettablue]

As a system builder, I know how to build a computer pretty much from scratch, but the systems I have built are all newer gaming type machines with massive amounts of memory, processors and high end peripherals.

So, my friend and I are starting the rebuild of the donor 5150 this weekend. When done, our plans are to leave it with only one 360 K floppy drive, 256 K of onboard RAM, a parallel port and monochrome display card, and that's pretty much it. We have a NOS 5150 revision B mother board with processor, and an XT power supply to get started. Most importantly is that the 5150's case is in perfect shape as well as the original keyboard. We're also keeping the original internal cables, wiring and whatever else we can re-use. Do we need to be aware of anything else while rebuilding this computer?

I also want to replace any missing expansion bay covers and drive bay cover. Where can I get these? Will the expansion slot covers from a new PC fit the 5150 case OK?

When this computer is done, I'm giving it to my friend. The only thing he will need then, is a monochrome monitor to complete the system.

 

[pearce_jj]

Just doing a similar project myself as it happens.

The original 5150(b) PSU I have in mine has awful RIFA X2 caps in it, which will need replacing (note the PSU will still run the machine with these completely blown).

Potential problems on the board, I am informed, are most likely to be in the bead caps, RAM or BIOS chips.

Here's a floppy disk head alignment idea, in case you should need it:
http://www.classic-computers.org.nz/blog/2010-06-28-alignment-tandon-m100.htm

Painted finish of the case (basically all of it) cleans up well with car polish i.e. Autoglym, and keyboard casing too.

Note HD disks won't work properly in DD drives.

Looking for a drive bay cover myself too!

 

[modem7]

Potential problems on the board, I am informed, are most likely to be in the bead caps, RAM or BIOS chips.

I've just done a bit of a search of these forums looking for threads covering faulty PC family motherboards.
The results are at http://members.dodo.com.au/~slappanel555/vcf_motherboard_failure_history.htm

 

[bettablue]

The 5150 Mark ll project has been going great! Even though my wife isn't all that much assistance in the actual project, she can at least help move things around a bit so I can do what I need to do inside.

I have the computer's case looking better than brand new. All it took was a good cleaning and a little car polish. The power supply, mother board, mono video card, floppy controller, parallel and serial cards installed and the computer boots up to BASIC with no problems at all! The mother board did come with 256K of onboard RAM, so we're currently leaving the memory expansion out till I find one that tests good. The one that came out of the computer is only reading 304 out of 384K I knew that was going to be a bear to figure out, and it was. Yes, I did swap them around and was able to locate, I hope, all of the bad ones. So, there were two that tested bad, one, a 64K and the other a 16K. Once I locate replacements, I'll reinstall the memory board too.

I won't know how everything else will really work though till the floppy drive is installed. (Remember, I'm only installing one drive, and I'm also not planning on installing a hard disk just yet.) I still need a cover plate if anybody has one. Still, when I power it up, there are no warning beeps, so I guess I got my IRQs set OK.

I wasn't expecting it to go that easily. And, it was a lot of fun locating the bad memory chips.

I'll keep you all updated.

 

[pearce_jj]

Great stuff, and good luck with sorting that RAM board. Did you open the PSU?

I'm trying to locate a drive bay blank too!

 

[bettablue]

No, I haven't opened the PSU. Is there a reason I should? The power supply and mother board were NOS I found on E-Bay. They both look like new and so far there doesn't seem to be any problems with either. I just wish I could find a front panel. With that, the computer will be ready for my friend to take home and use as he will. He's been drooling over mine ever since I got it and my 5160.

Great stuff, and good luck with sorting that RAM board. Did you open the PSU?

I'm trying to locate a drive bay blank too!

 

[pearce_jj]

I only mention the PSU because if it's a 5150 unit, it may have RIFA surpression caps in it, which will likely explode in a big puff of smoke at some point! Harmless fortunately!

 

[bettablue]

So, I took the computer apart to get the power supply out and open it up. Yes, those caps are the worst, but for now, they all look like they're in good shape. None are blown. So, I buttoned it back up.

Good news too. Today, the last of the floppy drives came in. I installed one, as planned, and the computer runs fine. I noticed that I was smelling a bit smoke after we had it powered on for a while, so we opened it back up and found two of those damned tantalum capacitors on the mothr board blew out. The computer still runs fine, but we're going to replace them all with modern equivalents.

So far, other than the capacitors, this machine went together pretty quickly. It only took about 3 hours of actual work to get it where it is. We'll be replacing the caps tomorrow.

On another note, my primary 5150 is also working perfectly too. The drives I had repaired by Chuck G came in today too. Once they were installed, everything was perfect! I ran a complete set of diagnostics from the IBM guide to Operations disk and everythin passed with flying colors. Funny thing on this one. It wass manufactured in 1984. There are no blown caps and the motherboard only has 64 K of RAM. The expansion card inside brings it to a total of 640, so someone spent some money buying this thing when it was new. Too bad they didn't spring for the serial port card though. Any way, it's working great and now that it is, I am a very happy geek!