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IBM PC 5150 displays 601 on boot

5150

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I'm having some problems on startup of my IBM 5150.

Here's what happens:
- Cursor starts blinking
- Red light of floppy drive comes on
- 601
- Red light off
- 1 short beep
- Red light comes on again
- Computer starts in Basic
- Red light off

There is no floppy in the drive because I don't have a floppy yet.

I understand that 601 has to do with the floppy drives.
How do I solve this problem?
Where do I start?
Could it be de controler?
Or are my floppy drives damaged?
 

5150

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reaction from other thread:
Do you have two floppies? If not, block 1 switch 7 should be on.

When it starts in Basic it only shows 64k is correct. :) It will only show 256k in DOS.

Yes I have 2 floppy drives.

I set the switches as shown on this page: http://www.selectric.org/ibmpc/switches.jpg
Switch block 1 = off, on, off, off, off, off, off, on
Switch block 2 = on, off, off, on, on, off, off, off

My configuration:
- IBM PC 5150 with 2 floppies (full hight 360KB)
- No math coprocessor
- 16-256kb motherboard filled with 256kb
- Monochrome display with Hercules graphics card

On boot the red light of the first floppy comes on.
Looking inside the drive I see the spindle turning.
I don't see or hear anything moving.

I then swapped the interface cable (the flat one that connects the floppies with the controller card) so it starts from the second floppy.
Same thing happens.
On boot a red light comes on.
Spindle starts turning.
Error 601, then Basic.

:angry:

On testing there were no floppies in the drives.

What should I look at / test next?
 
Last edited:

modem7

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On testing there were no floppies in the drives.
No floppies are required.

On boot the red light of the first floppy comes on.
Looking inside the drive I see something spinning around.
I don't see or hear anything moving.
The first time the red light comes on is when the Power On Self Test (POST) checks the floppy drive.
During that test, you are seeing the spindle turn, which is good.
But you should see/hear the drive's head assembly move (heads move to track 34).

It sounds to me like the lubrication on the metal rails within your drives may have deteriated to the point where the stepper motor can't move the heads.
Try removing what is left of the lubricant and then relubricate. A silicone based lubricant is recommended.
 

modem7

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Do I have to open up the floppy drive for that or can it be serviced as is (through the front or sides)?
I'm pretty sure that you will need to 'open' the drive.

tandon_tm100_rails.jpg
 

modem7

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Will a cotton bud dipped in some alcohol do for cleaning the rails?
That is what I do.

I guess I shouldn't be touching or moving the head when cleaning the rails?
The 'block' that slides on the rails is what I refer to as the head assembly. Yes, avoid touching the head end of that. The other end (right in the photo) is fine to grab and use to manually slide the head assembly along the rails (when power to drive is removed).

With no power to the drive, the head assembly should move relatively freely on the rails. You'll feel some resistance presented by the stepper motor (even with no power to the motor). Different models of stepper motor present different amounts of resistance, but in the TM100s that I have, the resistance is what I consider as light.
 

5150

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That is what I do.
With no power to the drive, the head assembly should move relatively freely on the rails. You'll feel some resistance presented by the stepper motor (even with no power to the motor). Different models of stepper motor present different amounts of resistance, but in the TM100s that I have, the resistance is what I consider as light.

You seem to have nailed the problem.
The head assembly is stuck like syrup to its rails.

Opening op the drive was easy.
Visualy everything looks clean and almost new.
I'm going to take my time cleaning those rails.
Hopefully it'll solve the 601 error.
 

5150

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Rails are clean and lubricated on both my drives.
Head assemblies run freely now (with some resistance from the stepper motors)
Still 601 error on boot up. Grrrrr!!! :confused:
No movement what so ever of the head assembly on boot up.
What should I be looking at next?
 

MikeS

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Can't get at my PC or XT at the moment so I have to ask: what should happen with the drives completely disconnected?

Seems to me that without a disk the only thing the controller can check is stepping off and back on to track 0?

Since the light comes on it's probably not relevant, but is the terminator installed and the jumpers correctly set?
 

Stone

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As it's very unlikely that both floppy drives have failed it seems likely that the controller is the culprit. You'll need to either try another floppy controller or test one or both of the floppies in another computer.
 

Stone

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I guess the terminator and jumpers are where they're supposed to be because I didn't change the machine's configuration since I last used it 20 years ago.
The jumpers should be OK but if you tried the original drive B on the end of the ribbon cable instead of the original A the terminator is probably incorrect. So you might need to move the terminator from one drive (original A) to the other (original B) in order to get the original B to boot the machine. You do have a floppy boot disk by now, don't you? :)
 

MikeS

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So what exactly should I be doing with the terminator? (what is a terminator? / where is it located? / what should I change?)
As you say, if it was working once the way it is and you haven't changed anything then the terminator and jumpers probably don't have anything to do with your problem; never hurts to ask though.

One (and only one) of the drives should have what looks like an IC in the 16-pin socket closest to the connector; it should be in the A drive at the end of the cable, but in practice it doesn't really matter as long as one of the connected drives has it installed. The only time you might have to move it is if you wanted to connect the original drive B (in either location) by itself, i.e. without drive A (which has the terminator) also connected.

I'm still curious what error (if any) one should get with the switch set for floppy drive(s) but no drives connected, and with the controller completely removed for that matter, and if that's what you get.
 
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