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external floppy for 386SX

K

kerravon

Experienced Member
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Oct 31, 2021
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137
I have an 80386SX laptop, which works for a couple of minutes every now and then (days apart).

I would like to boot from an external floppy as the internal floppy is giving issues and it might be the drive.

Is this a standardized connector at all? If so, what is it called and can I connect anything, preferably something new, to it?

Thanks. Paul.


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No real standard for external floppy connectors. That looks like the style used by IBM, Toshiba, and Apple. Sometimes, they used different pinouts for the same connector. https://www.thinkwiki.org/wiki/Floppy_Connector gives a quick explanation. Even if you find a drive from the correct brand with the correct connector, it might not work with the specific model you have.
 
krebizfan said:
No real standard for external floppy connectors. That looks like the style used by IBM, Toshiba, and Apple. Sometimes, they used different pinouts for the same connector. https://www.thinkwiki.org/wiki/Floppy_Connector gives a quick explanation. Even if you find a drive from the correct brand with the correct connector, it might not work with the specific model you have.
Click to expand...

I read the link - thanks.

From the link there was also mention of a "port replicator" and also that you can blow a fuse if you get the wrong drive.

Is it possible to use a multimeter to confirm what I have before plugging anything in?

And ideally I would have it connected to a modern machine emulating a floppy disk. Is that not possible?

This laptop was made in Taiwan and I can't see a sensible model number. It was distributed in Australia. But has an FCC ID of HGEARC3025.

Also there is a bit of information in the manual. It says that you plus a 25-pin plug into the floppy drive, and the D connector into the computer.

Just from the tone of the manual it seems that they consider external floppy drives standard. So maybe cheap computers were effectively standardized on Toshiba?

Thanks. Paul.
 
Post a photo of the laptop, I'm pretty decent at identifying laptops. Looks like it was made by Plus & Plus Co: https://fccid.io/HGEARC3025
Your non-booting issue sounds like you have some weak capacitors.
 
3lectr1c said:
Post a photo of the laptop, I'm pretty decent at identifying laptops. Looks like it was made by Plus & Plus Co: https://fccid.io/HGEARC3025
Your non-booting issue sounds like you have some weak capacitors.
Click to expand...

This is what I bought:

www.ebay.com.au

Vintage Notebook 386SX/25 Computer 6MB *TESTED & WORKING - W/ Case ETC* | eBay

HAS MS DOS INSTALLED, when turned on, the drive format needs to be changed and it can successfully boot in dos.
www.ebay.com.au

Are you able to see that?

My issues with the hardware are:

1. Memory test says 2 MB extended RAM approx, but I believe there is 4 MB.

2. Screen is normally black. After letting it rest for 24 hours or something there is a 20% chance that the screen will come back.

3. Even if the screen has something, it is normally only good for seconds, before it goes crazy. But this isn't a problem because I can use an external monitor. But the monitor doesn't show anything if the internal screen was originally black.

4. Floppy did boot when I got it, but didn't reach the minimum memory requirements for PDOS/386 (4 MB total). I trimmed PDOS/386 down so it will accept 2 MB, but now the floppy doesn't boot, but it may not be a floppy problem.

5. System said the floppy drive was bad today.

6. It won't let me set the amount of memory to 4 MB or even disable it - it keeps doing its own tests and insists on setting it to 2 MB. Even if I press a key to skip the memory test.

7. Setting the hard disk type to 24 gives me the 40 MB default hard disk described in the manual, and it does say the word MSDOS, but HIMEM tests upper memory and never comes back. Not sure if changing RAM wait times or something in the BIOS might help.

BFN. Paul.
 
I see. I've maybe seen a listing for a similar one in the past but I'm not familiar with that model.

RAM fault - I'd reseat any internal RAM cards and see if that solves it. Something could have come loose in shipping. Alternatively, that RAM may have simply failed.

Booting issue - This could also be the RAM, although I'd expect it to give some error beeps or something to that effect if a RAM fault was stopping POST. More likely, the PSU or an internal DC/DC board inside the laptop has some bad capacitors that need replacing. This is extremely common in computers from this error.

Screen "going crazy" - If you can get photos of that then I can probably know for sure, but it definitely sounds like bad capacitors to me. Does it look like the contrast is drifting all around, or does the picture on the screen go all corrupt? Either way, this behavior can be explained by bad capacitors. This is a common fault on these early LCDs, especially those made by Sharp, although other brands can have this happen too. It could also be a loose display connector.

Floppy issue - Could possibly related to the power issue, but it's just as likely to be a dirty head, stiff head motor that needs lubrication, or even a bad belt if the drive motor is belt-driven. Let's hope it's not a bad belt, as sourcing a new one can be a challenge. It's also always possible that the floppy drive itself could have some capacitors on it that have failed. Only way to know is to open the system up and start investigating.

Keep a lookout for anything resembling a CMOS battery when you take it apart as well. There's a solid chance that whatever type of CMOS battery it uses is one that's prone to leaking, and should be removed.

Good luck! Sounds like it's gonna take a bit of work to get it fully operational again, but it definitely seems fixable to me.
 
3lectr1c said:
RAM fault - I'd reseat any internal RAM cards and see if that solves it. Something could have come loose in shipping. Alternatively, that RAM may have simply failed.
Click to expand...

I'm actually interested in using PDOS/386 to diagnose the problem. If I can get it to start from the hard disk, or even that external floppy, I can start inspecting what is happening.

(basically I have non-standard interests - and I can live with it only working for 2 minutes at a time)

3lectr1c said:
Screen "going crazy" - If you can get photos of that then I can probably know for sure, but it definitely sounds like bad capacitors to me. Does it look like the contrast is drifting all around, or does the picture on the screen go all corrupt?
Click to expand...

It's totally corrupt. Light exists (lots of light (pixels lit)), but that's all. No characters can be seen. I don't have a photo currently.

And as I said - I don't mind this, as the external monitor saves the day. The big problem is when the screen is black. I suspect the video card itself is failing, preventing an external monitor from working.

3lectr1c said:
Floppy issue - Could possibly related to the power issue, but it's just as likely to be a dirty head, stiff head motor that needs lubrication, or even a bad belt if the drive motor is belt-driven. Let's hope it's not a bad belt, as sourcing a new one can be a challenge. It's also always possible that the floppy drive itself could have some capacitors on it that have failed. Only way to know is to open the system up and start investigating.
Click to expand...

Ok - again - my interest has shifted to the external floppy.

In 2023 do we not have the ability (ie a device) to connect an arbitrary set of pins (ie the D connector) to some USB cable to allow software on a modern machine to emulate a floppy disk?

3lectr1c said:
Keep a lookout for anything resembling a CMOS battery when you take it apart as well. There's a solid chance that whatever type of CMOS battery it uses is one that's prone to leaking, and should be removed.
Click to expand...

Ok, the CMOS is definitely dead which is why I need to reset the BIOS each time. The seller to the seller said that needed to be done, but no-one wrote down the instructions. I knew that the instructions were missing before buying the machine but expected to be able to guess the answers, and I also expected the previous guy to eventually answer the email.

3lectr1c said:
Good luck! Sounds like it's gonna take a bit of work to get it fully operational again, but it definitely seems fixable to me.
Click to expand...

Sounds good! But I'm more in "antelope mode" at the moment.

www.linkedin.com

How to report bugs?

A very insightful read by Simon Tatham How to Report Bugs Effectively How to Report Bugs Effectively by Simon Tatham, professional and free-software programmer Introduction Anybody who has written software for public use will probably have received at least one bad bug report. Reports that say nothi
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I'd like a photo of the LCD. Sounds a bit like standard behavior when it isn't receiving/able to process a signal, or if the capacitors are bad. Basically the backlight shining through but no image? Like if you turned the contrast all the way down? Certainly sounds like power issue or bad caps to me.

I highly doubt the video card is failing, unless it's still giving a post beep or something even in the no-display state. I'm nearly certain you have an intermittent connection somewhere, or more likely, bad electrolytic capacitors someone in the power circuits. Extremely common for the time.

There is such a thing as a modern floppy emulator, called the Gotek. It should be possible to build an adapter to anything that uses the standard floppy protocol for PCs (someone did it for the Citizen W1D drives found in many laptops that used a proprietary cable). Biggest hurdle there is getting the pinout of the floppy port. That thing is big enough though that I wouldn't be surprised if it just uses a standard desktop floppy drive inside, which would make things easy.
 
3lectr1c said:
I'd like a photo of the LCD. Sounds a bit like standard behavior when it isn't receiving/able to process a signal, or if the capacitors are bad. Basically the backlight shining through but no image? Like if you turned the contrast all the way down? Certainly sounds like power issue or bad caps to me.
Click to expand...

There is an image - total junk, I think moving. Nothing readable. I'll try to get a photo.

3lectr1c said:
I highly doubt the video card is failing, unless it's still giving a post beep or something even in the no-display state. I'm nearly certain you have an intermittent connection somewhere, or more likely, bad electrolytic capacitors someone in the power circuits. Extremely common for the time.
Click to expand...

It does make something like a beep sometimes.

3lectr1c said:
There is such a thing as a modern floppy emulator, called the Gotek. It should be possible to build an adapter to anything that uses the standard floppy protocol for PCs (someone did it for the Citizen W1D drives found in many laptops that used a proprietary cable). Biggest hurdle there is getting the pinout of the floppy port. That thing is big enough though that I wouldn't be surprised if it just uses a standard desktop floppy drive inside, which would make things easy.
Click to expand...

I looked up the Gotek - looks good. What do you mean by "the floppy port"? You mean the D connector? It sounds like there are only a few different sorts there. Can I get one cable for each so that I'm covered no matter what PC I have? And then connect that to the Gotek.

Or is it only possible to use the Gotek inside the machine, or connected to something inside the machine?

Note that I am still surprised you need a specialized device like that. I expected to be able to connect the D connector to some sort of "magic box" that had like 50 generic pins that could do input and output up to 12 V and then you electronically control that "magic box" via USB cable. Then the world of software can take over.

Note that I dropped out of Electrical Engineering and (after a timeout) switched to Computer Science for a reason. :)
 
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I found this in the manual - so hopefully this makes sure I get the right D connector.

Someone pointed me to this:

www.ebay.com

Toshiba PA2611U 3.5" Floppy Drive External FDD Attachment Case & Cable | eBay

Find many great new & used options and get the best deals for Toshiba PA2611U 3.5" Floppy Drive External FDD Attachment Case & Cable at the best online prices at eBay! Free shipping for many products!
www.ebay.com

I'm happy to buy that for now, but eventually would like the ability to buy something new for this situation.

This situation being a working hard disk, which is all I want, but I need to be able to boot from something else (or put the drive in a chassis), so that I can format it (with PDOS/386).
 
There has been massive progress!

It booted from floppy, with caveats.

Here is the result after the boot.


Another breakthrough was that it started detecting 4480 KB of extended memory at one point. Once it said 4096 KB. But it didn't last long and it was back to the normal 2 MB. And then even conventional memory failed the memory test.

I didn't manage to really catch the crazy screen (lots of horizontal lines). This time there was only a small number of lines, and even those faded so you probably can't see them by the time I got the camera ready. But as usual - no big deal, the external monitor works around that problem.

It only takes about 3 minutes to boot from floppy, not bad considering the lousy sector-at-a-time reading.

I didn't manage to get a photo of it booting from floppy and detecting the hard disk, because then it went crazy with PE errors, likely due to bad floppy disk reads, and I was silly enough to think that it was going to work fine so didn't need to take a photo immediately.

I'll post some photos now.
 
That "A" is meant to be in yellow, and the blue is only supposed to be on the first line. I suspect a BIOS limitation there. But can't really debug it with so little time on the machine (like 10 minutes per day if I'm lucky). And I'm not particularly trying to debug BIOSes. I only wanted to check that PDOS/386 used only valid 80386 instructions. Instead of having total trust in emulators.
 
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First boot from floppy went haywire. It was exposed to, and detected, a hard disk that time - so it wasn't a controlled experiment. However, I doubt that the hard drive had anything to do with this. I suspect that the floppy disk failed to read command.exe properly and was thus corrupt.
 
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This is what my "crazy screen" now looks like. The screen was initially readable, but said that it had a configuration error and I needed to press F2. But pressing F2 to get into the BIOS setup gives me junk instead.

I'm pretty sure it sometimes works. And the junk had much more lines before, and I'm pretty sure they used to move. But the junk screen has changed, and I'm not sure how many variations of junk are required to pronounce the screen dodgy. And again - I don't care - the external monitor is good enough for what I am trying to achieve.

It would still be good to have a decent external floppy drive though - preferably new and emulated, as I just need a means to get to the hard disk. I don't really need a working floppy.

Although come to think of it - a real external floppy would solve an unrelated problem - I want to be able to read my Windows 95 disks which come in DMF format. And also my IBM PC DOS 7 disks, which come in another format. I can't use my USB floppy to read these.

I know I can just download them - but I don't want to do that.

But these are independent goals. Basically I want to be able to read data from my MFM drive. I can do that via COM port, but I need to get PDOS/386 on there first. So a once-off use of external emulated floppy would be fine. And only if I corrupt the hard disk do I need to use the floppy again to reinstall.
 
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