Restoring IBM PC 5150

[JJF]

I'm trying to restore an IBM 5150 that I bought in the early 1980's has a 16-64k motherboard. Hard controller has failed (error 1701), 360k Tandon full height floppy won't read and the aftermarket expansion memory card doesn't seem to register. I'm also looking for parts and solutions. I'm lucky.... My PC boots into Basic when nothing else works.

I found an error code list at http://support.microsoft.com/kb/35436. I don't have a CGA tube so I'm using an ambery.com CGA to VGA converter. It works well.

But I'm looking for an 8-bit ISA controller for modern IDE PATA or SATA. Dangerous Prototypes has printed circuit board but not a complete controller. I'm looking for an 8-bit ISA controller modern for a 1.44 floppy. But I will take an old, working, reasonably price, and 360k floppy controller. I'm guessing the memory card is dead because the on-board Varta battery is shot. I found batteries at Parts-Express.com Varta 3/V100R P/N 141-105 or Varta 3/V60R P/N 141-102.

And, Oh yes, where can I get a copy of PC DOS.

I would very much appreciate any suggestions.

Thanks

 

[Ole Juul]

Welcome to the forums JJF!

I'm trying to restore an IBM 5150 that I bought in the early 1980's has a 16-64k motherboard. Hard controller has failed (error 1701), 360k Tandon full height floppy won't read and the aftermarket expansion memory card doesn't seem to register. I'm also looking for parts and solutions. I'm lucky.... My PC boots into Basic when nothing else works.

In cases like that when there are multiple problems it is generally best to start at the beginning. Take everything out. Make a note of what slots things were in, and all original switch settings. Then put the video card back, and see how that goes. Remember that there is no editable BIOS, but there are two switch blocks on the MB which need to be set correctly. We can guide you here with all that. It would be helpful to know which of the BIOS versions you have though.

And, Oh yes, where can I get a copy of PC DOS.

Easy to find on eBay and elsewhere. Perhaps somebody close by can slip you a boot disk too. In the end you may want to get something historically correct, but DOS 3.3 is about the best choice otherwise. It doesn't matter if it is IBM or MS.

 

[modem7]

Whereabouts (town/country) in the world are you? A close neighbour with some expertise may be willing to 'drop in'.

It would be helpful to know which of the BIOS versions you have though.

In this case we can deduce that. The OP is seeing a "1701" error. In a PC or XT class computer, the code in the hard drive controller's BIOS expansion ROM produces that. Only the third (and final) BIOS for the 5150 is aware of and executes BIOS expansion ROMs.

 

[modem7]

Hard controller has failed (error 1701),

The hard disk drive is also a possibility (amongst other less likely causes)

I'm guessing the memory card is dead because the on-board Varta battery is shot.

Your memory card may in fact be a multifunction card, where RAM is just one of the functions provided by the card, and a battery-backed clock is one of the other functions.
A photo of the card will help us a lot.
Where Ole Juul is coming from is the posibility that the motherboard switches may not be correct set for the amount of RAM you have (motherboard + RAM on cards), however, if you tell us that you haven't touched the switches since you bought the machine in the eighties, then I guess we can rule out motherboard switch settings (although there would remain the possibility of a dirty switch contact)

 

[modem7]

Hmmm. The 5150 does not show a RAM count as it starts, and you presently can't boot to DOS.
So how are you determining that RAM is 'missing'?
If you are looking at the figure displayed when BASIC starts, then note that that figure is not indicative of total RAM.

 

[Ole Juul]

In this case we can deduce that. The OP is seeing a "1701" error. In a PC or XT class computer, the code in the hard drive controller's BIOS expansion ROM produces that. Only the third (and final) BIOS for the 5150 is aware of and executes BIOS expansion ROMs.

Excellent deduction.

Anyway, I'm also concerned that he said that the "floppy won't read". Won't read what? I think this is all a bit of a rat's nest (of information) and it might be a good idea to get some clarification and look at everything one item at a time.

 

[JJF]

Thanks so very much for your replies and advice.

The machine’s serial number is 0149970. Bios is P/N 1501476 dated 1981 1983 D Dallas MK36C35-4 chip. This is not the original bios. To upgrade bios, IBM required a physical swap of the chip. I bought the machine at the IBM store located in the Oak Brook, IL mall (Oak Brook is a suburb west of Chicago). I ordered the bios upgrade and when it came in, I popped the bios out of the machine and drove chip to Oak Brook for the swap. IBM was a bit paranoid about their Bios... I guess, in retrospect, with good reason.

The memory card is a multifunction card; printer, clock, 15 pin female, 15 pin male which I suspect are game ports. I only cared about the memory and the printer. I'm judging the amount of memory by the amount stated when basic starts. I gather from Modem7's comment that this is not the amount of RAM actually recognized.

With a DS DD floppy in place, the 360k floppy spins and grunts and the machine hangs. Without the disk, the machine boots to basic.

I have not yet rocked the dip switches to clean contacts.

As I see it, the next steps are to get a good copy of DOS and then get the Floppy to read it.

Thanks for your help.

 

[modem7]

I gather from Modem7's comment that this is not the amount of RAM actually recognized.

Correct.

In the 5150, the person configuring the 5150 sets the total amount of RAM (motherboard + expansion cards) into the switches in motherboard switch block SW2.
So, by looking at the setting of SW2, you can work out what RAM (total) the POST (power on self test) is expecting to find.
Information about SW2 setting can be found [here].

With a DS DD floppy in place, the 360k floppy spins and grunts and the machine hangs.

For the 5150 to boot to DOS from the floppy drive, that "DS DD floppy" floppy specifically needs to be a DOS boot floppy.
Is that floppy a known DOS boot floppy, or simply a floppy you had stored with the 5150 ?

As I see it, the next steps are to get a good copy of DOS and then get the Floppy to read it.

Whereabouts (town/country) in the world are you? Someone nearby may post you a 5.25" DOS boot floppy.

In the meanwhile, some things to try:
1. With power off, reseat the floppy controller card: out then in. I suggest three times.
2. Relubricate the rails in the floppy drive. See procedure [here].

 

[Trixter]

I don't have a CGA tube so I'm using an ambery.com CGA to VGA converter. It works well.

Which one? And how does it handle the upper eight colors (the "bright" ones)?

 

[Trixter]

I bought the machine at the IBM store located in the Oak Brook, IL mall (Oak Brook is a suburb west of Chicago).

If you are still in Chicago suburbs, I can provide you with any 5.25" floppies you need, as I'm local. email me privately at trixter at oldskool dot org if you want to set something up.

 

[JJF]

Hi Trixter,

Thank for the reply.

"I don't have a CGA tube so I'm using an ambery.com CGA to VGA converter. It works well."

"Which one? And how does it handle the upper eight colors (the "bright" ones)?"

The CGA to VGA adapter is a Ambery AV-1. I don't know how it handles the bright colors. I was simply interested in getting something on the screen.
The only think I found crazy about the adapter is that it requires a special cord. I looked at the Chinese boards made for stand-alone game machines. I bought this because I didn't want to make the effort to put one of their board in a box.

As for the memory card and Tandon drive that you have for sale. I don't think the memory card is an issue at this point in time. I'm much more interested in get the floppy and hard dive disk systems running. Your Tandon may be a solve for the floppy problem. I don't know yet.

I live west of Chicago so setting up a swap, if I need the drive, won't be a problem.


Best regards, JJF

 

[Stone]

I still have one of these left:

http://www.vintage-computer.com/vcforum/showthread.php?25760-NEC-(and-other)-multisync-monitors

One monitor for all your computing needs, e.g., mono, CGA, EGA and VGA.

I've also got a very nice EGA monitor in excellent condition.

 

[Trixter]

The CGA to VGA adapter is a Ambery AV-1. I don't know how it handles the bright colors. I was simply interested in getting something on the screen.

Thanks for the clarification. According to the manufacturer's site, the I pin is wired to "NC" which I'm assuming stands for No Connection, so the adapter does not display the latter 8 colors, which is common for arcade "CGA2VGA" adapters. If you run my CGA Compatibility Tester on that setup, you can verify the upper 8 colors look just like the lower 8.

As for the memory card and Tandon drive that you have for sale.

You have me mistaken for someone else; I was only offering to send you some disks.

I live west of Chicago so setting up a swap, if I need the drive, won't be a problem.

Happy coincidence, I also live 40 minutes west of Chicago. Maybe it would be better for you to physically visit me with your machine, that way we can debug it better. I have some spare parts. Email me.

 

[JJF]

Hi everyone.... Apparently my last post didn't make it into the thread... my problem. If this is a duplicate, please forgive me. First, the www.minuszerodegrees.net site has a wealth of information. Thank you. And the www.vintage-computer.com provide great access to knowledgeable people. Thank you everyone.

Here is the status on my restoration of an IBM 5150 PC, 16-64k with IBM CGA, 1 Floppy, St-251 Hard Drive with WDXT-GEN controller, 1.5 meg (don't laugh, it's overkill but it was cheap at the time and proved to be solid) Magnum mastercard memory-multifunction card : CGA worked so I pulled the hard drive controller and memory board and worked with several different floppy controllers and floppy drives. The best I could do was this: the floppy would grunt and a single short beep followed by boot to Basic. Memory card appeared to function; the floppy and the hard drive did not. So then I began to think the motherboard was bad.

I bought an adapter and burned an AT28C64B with diagnostics and replace U33. The diagnostic showed repeatable failure of the Intel 8237A DMA, slow refresh and sporadically bad bits. Sporadically bad bits I can blame on slow refresh. But, here is what puzzles me: A bad DMA or a slow refresh timer should have halted the machine during post; but the 5150 posted OK. I assume my PC posted OK because methodology used in the IBM post is less stringent that the methodology used by the diagnostic. So here are my questions: is there a common component that would cause the DMA failure and the slow refresh? If so, what component is it? I do not like the prospect of (me) replacing chips on the motherboard. And I don't seem to be able to find a replacement 16-64k motherboard.

The good news is that I also found out, using a working 64-256k motherboard, that my memory card, floppy drives and floppy controllers are OK. The hard drive is still non-functional.

 

[modem7]

A bad DMA or a slow refresh timer should have halted the machine during post; but the 5150 posted OK. I assume my PC posted OK because methodology used in the IBM post is less stringent that the methodology used by the diagnostic.

That would be it. The POST is essentially a crude confidence test only.

is there a common component that would cause the DMA failure and the slow refresh? If so, what component is it? I do not like the prospect of (me) replacing chips on the motherboard.

It depends on exactly what the diagnostics mean by "slow refresh". Depending on the answer, a number of chips could be candidates.

But according to the 1986 dated post at [this] link, the 8237A DMA chip is a common failure on 16KB-64KB motherboards.

Unstable +5 volts may be another possible cause. Perhaps a power supply outputting excessive ripple, but not enough to cause the POWER GOOD signal to drop. Perhaps one or more tantalum capacitors near the DMA chip going open circuit.

To date, the failures of my 16KB-64KB motherboards have been due to faulty RAM chips.

 

[fjk61011]

Whereabouts (town/country) in the world are you? A close neighbour with some expertise may be willing to 'drop in'.


In this case we can deduce that. The OP is seeing a "1701" error. In a PC or XT class computer, the code in the hard drive controller's BIOS expansion ROM produces that. Only the third (and final) BIOS for the 5150 is aware of and executes BIOS expansion ROMs.

1701 is the registry number of the Starship Enterprise