The floppydrive should have a resistor network on the pcb near the connector for termination.
On some really old drives you could remove the resistor network, on newer drives it is not removable.

DerBaum wrote on 2023-11-19, 22:50:

The floppydrive should have a resistor network on the pcb near the connector for termination.
On some really old drives you could remove the resistor network, on newer drives it is not removable.

You're right, I just measured resistance with everything hooked up over the second connector on the cable. Everything is roughly 500-600 ohms, except there's no continuity on pin 16 (Drive Select B) and pin 12 (Motor Enable B) and reserved pins 4 and 6. That seems to be normal then. Could the Super I/O chip (NTC6776D) be bad? Are there ways to test it without an o-scope?

Just because it's easy, and it works as 5.25
I'd flash the bios to be sure it's not just some random corruption.
I'd probably also chuck it in the dishwasher to rule out weird dust issues but most people baulk at that
(no soap if you do it)

myne wrote on 2023-11-20, 00:27:

Just because it's easy, and it works as 5.25 I'd flash the bios to be sure it's not just some random corruption. I'd probably al […]
Show full quote

Just because it's easy, and it works as 5.25
I'd flash the bios to be sure it's not just some random corruption.
I'd probably also chuck it in the dishwasher to rule out weird dust issues but most people baulk at that
(no soap if you do it)

Reflashed (again) and no change in behavior. I'm not going to throw it in the dishwasher. It's a pretty rare board now and it's already very clean.

Yeah do not wash it. The only thing you can do is use an external USB floppy drive since the board has no ISA slots, or replace the Super I/O chip but you should make sure that it is the problem first...
It is known that on some boards the buffers for the floppy controller part were very weak and just connecting a drive backwards would kill the controller part, rare but it can happen.
Have a similar board where the USB ports died but everything else works so am using a PCI add-on USB card....not that that helps but shows how weak certain sections are with age...

Horun wrote on 2023-11-20, 03:13:

Yeah do not wash it. The only thing you can do is use an external USB floppy drive since the board has no ISA slots, or replace the Super I/O chip but you should make sure that it is the problem first...
It is known that on some boards the buffers for the floppy controller part were very weak and just connecting a drive backwards would kill the controller part, rare but it can happen.
Have a similar board where the USB ports died but everything else works so am using a PCI add-on USB card....not that that helps but shows how weak certain sections are with age...

The Asus P5K's ICH9 driven USB ports had a tendency to die in just such a fashion, AFAICR. And that was when the thing was still reasonably current tech.

VDNKh wrote on 2023-11-20, 02:17:

Reflashed (again) and no change in behavior. I'm not going to throw it in the dishwasher. It's a pretty rare board now and it's already very clean.

I have an older revision of this board. If you need any component values, you can ask here. To wash boards, use a toothbrush or soft bristle brush and your favourite mild lemon cleaner (Mr. Clean). Spray liberally, brush brush brush, rinse, brush, and then you need to blow out all the water with warm, high pressure air. The air stream needs to be focused through a narrow nozzle so you can get under the memory slots and BGA chips.

If you don't have a way to blow out all the water, then don't wash your board... I see a lot of people on Youtube letting their boards 'air dry'... Don't air dry your board or dry it in the sun. There will be plenty of water left over corroding the solder.

mockingbird wrote on 2023-11-20, 05:14:

VDNKh wrote on 2023-11-20, 02:17:

Reflashed (again) and no change in behavior. I'm not going to throw it in the dishwasher. It's a pretty rare board now and it's already very clean.

I have an older revision of this board. If you need any component values, you can ask here. To wash boards, use a toothbrush or soft bristle brush and your favourite mild lemon cleaner (Mr. Clean). Spray liberally, brush brush brush, rinse, brush, and then you need to blow out all the water with warm, high pressure air. The air stream needs to be focused through a narrow nozzle so you can get under the memory slots and BGA chips.

If you don't have a way to blow out all the water, then don't wash your board... I see a lot of people on Youtube letting their boards 'air dry'... Don't air dry your board or dry it in the sun. There will be plenty of water left over corroding the solder.

Would soaking the board in 99% isopropyl alcohol after a water based washed and then air drying be a reasonable option ?

I've used a warm oven to dry GPUs. ~90C for 10-15 mins. I've also used oil heaters and time, and just plain air and time. No high pressure.

But you say it's clean, so let's focus on the controller.
I believe based on a goggled image, it's this:

https://pdf1.alldatasheet.com/datasheet-pdf/d … N/NCT6776D.html

Page 10 of the datasheet starts on about the fdc.
Best to start checking components that connect to pins 2-14.

Could be as simple as an open resistor, or a shorted cap.

Reading the datasheet, and what you've written, my gut says pin 7 is prime suspect. I'm assuming that 1.2mb and 1.44 behaved differently as far as navigation and stepping tracks goes, but hey it's a place to start.

darry wrote on 2023-11-20, 05:38:

Would soaking the board in 99% isopropyl alcohol after a water based washed and then air drying be a reasonable option ?

No, alcohol is a solvent, definitely don't do that. When I say "high pressure", you don't need anything fancy. Shop vacuums have a reverse-flow option where you attach the intake hose to the exhaust. Just make sure you take out the bag before you do that because it's going to blow whatever is in the vacuum out. Find a way to restrict the flow at the end of the hose to a narrow point. I hold a funnel to it with one hand and hold the board with the other. When you do it in the summer, you get warm air automatically from outside. It works in the winter too, but it's better to do it when the air is warm outside.

Isopropyl is the industry standard and strongly preferred method for cleaning all electronics at finishing and repair stages.
I'm very confused why you'd say that.

myne wrote on 2023-11-20, 21:42:

Isopropyl is the industry standard and strongly preferred method for cleaning all electronics at finishing and repair stages.
I'm very confused why you'd say that.

For spot cleaning, yes... Not for soaking things in. If you soak your board in alcohol, it's going to start dissolving things.

This topic is quite interesting to me as I've one motherboard revived with non-original BIOS and pretty much the same symptoms with FD-drives.

mockingbird wrote on 2023-11-21, 14:02:

For spot cleaning, yes... Not for soaking things in. If you soak your board in alcohol, it's going to start dissolving things.

And what things exactly will it dissolve? Plastics - no. Metal - no. Soldermask - no. Solder joints - no. Rubber - no. Water - yes!

In fact pure alcohol is pretty good for absorbing water.

Only rubber and certain plastics will IPA dissolve AFAIK. Have used it to clean many computer board parts and cpu tops but never gave a motherboard a full dip bath in it, ususally use a bunch of Q-tips, small paint brush, papertowel, etc.
And I only use 99% IPA, not the 50, 70 or 90% types as they contain too much water.

Alcohol (C2H5OH) isn't as aggressive as acetone or other solvents. I rinse boards with 95% medical/surgical spirit (ethanol) after cleaning in ultrasonic bath and never ever had any problems with dissolved or damaged plastics and rubber parts. After all the board doesn't need to be soaked for hours or even minutes in alcohol. The alcohol binds with the water molecules instantly and it all evaporates in a matter of minutes, long long time before any rubber or plastic dissolution process begins.

myne wrote on 2023-11-20, 06:55:

I've used a warm oven to dry GPUs. ~90C for 10-15 mins. I've also used oil heaters and time, and just plain air and time. No hig […]
Show full quote

I've used a warm oven to dry GPUs. ~90C for 10-15 mins. I've also used oil heaters and time, and just plain air and time. No high pressure.

But you say it's clean, so let's focus on the controller.
I believe based on a goggled image, it's this:

https://pdf1.alldatasheet.com/datasheet-pdf/d … N/NCT6776D.html

Page 10 of the datasheet starts on about the fdc.
Best to start checking components that connect to pins 2-14.

Could be as simple as an open resistor, or a shorted cap.

Reading the datasheet, and what you've written, my gut says pin 7 is prime suspect. I'm assuming that 1.2mb and 1.44 behaved differently as far as navigation and stepping tracks goes, but hey it's a place to start.

Haha, at least some people are on topic. I found the same document you did. I'll start taking more measurements after Thanksgiving. From the relevant pins on the controller, I should be looking for ~1000 ohms between the data pins and the 5v rail. I might need to get some more specialized attachments for pins that small. I can see the voltage fluctuations on the read pin, with my cheap multimeter at the floppy cable, but can't verify it's within spec without an o-scope.

Horun wrote on 2023-11-20, 03:13:

Yeah do not wash it. The only thing you can do is use an external USB floppy drive since the board has no ISA slots, or replace the Super I/O chip but you should make sure that it is the problem first...
It is known that on some boards the buffers for the floppy controller part were very weak and just connecting a drive backwards would kill the controller part, rare but it can happen.
Have a similar board where the USB ports died but everything else works so am using a PCI add-on USB card....not that that helps but shows how weak certain sections are with age...

I would really like to get the floppy port to work. All the other PCI ports are spoken for. USB could work but it just doesn't seem right, it's undignified. The crazy thing is, this is not an old board. The R3.0 variant of this board was made in 2012.

mockingbird wrote on 2023-11-21, 14:02:

myne wrote on 2023-11-20, 21:42:

Isopropyl is the industry standard and strongly preferred method for cleaning all electronics at finishing and repair stages.
I'm very confused why you'd say that.

For spot cleaning, yes... Not for soaking things in. If you soak your board in alcohol, it's going to start dissolving things.

As other people have echoed in the thread: IPA is harmless to printed circuit boards and their components. I've soak cleaned many electronics, old and new, and IPA has never caused any issues.

analog_programmer wrote on 2023-11-22, 08:16:

Alcohol (C2H5OH) isn't as aggressive as acetone or other solvents. I rinse boards with 95% medical/surgical spirit (ethanol) after cleaning in ultrasonic bath and never ever had any problems with dissolved or damaged plastics and rubber parts. After all the board doesn't need to be soaked for hours or even minutes in alcohol. The alcohol binds with the water molecules instantly and it all evaporates in a matter of minutes, long long time before any rubber or plastic dissolution process begins.

Yes but in many places one cannot get clean Ethanol that strong unless you have a license and Ethanol is not same as Isopropyl C3H8O. Each is derived from a different process. The most common one is IPA for quick drying and cleaning of parts because it is not controlled the same as drinkable ethanol 😀

analog_programmer wrote on 2023-11-22, 00:10:

This topic is quite interesting to me as I've one motherboard revived with non-original BIOS and pretty much the same symptoms with FD-drives.

Because I had only had two Sony MPF920 FDDs on hand, I got a different make and model FDD to test. A Mitsumi D359M3. Turns out the motherboard's floppy port works perfectly fine with this Mitsumi FDD. I guess the Super I/O chip doesn't like the Sony FDD for whatever reason. Maybe the terminator resistance to drive the read pin is too high on the Sony FDD? Who knows.

Anyway, thanks to everyone who replied.

Thanks ! And good to know ! So if anyone has an issue with their 1.44mb HD floppy drive check first to see if it a Sony. To me this is like a blast from the past. Had a new Sony cordless phone that didn't work proper from the start, it got replaced under warranty and within months also acted up. My friends used to joke about it as "that Sony phone". wow guess I should have asked what brand drive it was 😒