Help me restore access to my DOS machine's drive

[Ziggy]

Huh, that's kind of strange. Do the two coin cell batteries stack in one holder? Or are there two separate battery holders?

That's kind of strange that it doesn't specify a battery type in the manual, but at least it confirms it's 3v. When you say "larger" than 2032, do you mean the diameter? By the way, those numbers are the measurements, which might make it easy to determine what battery you need. 20 means it's 20mm diameter, and 32 means it's 3.2mm height. Do you have any digital calipers? You can use that to determine the diameter of the battery holder on your motherboard, and then it might be obvious what type of battery you need after learning that.

This page will help: https://en.wikipedia.org/wiki/Button_cell#Package_size

And this: https://en.wikipedia.org/wiki/List_of_b ... oin,_watch

Here's a cheap digital caliper that I bought off eBay a while back: https://www.amazon.com/gp/product/B07DF ... UTF8&psc=1

Definitely worth picking up for that price if you don't already have one. I have a few of them, and I got this cheap one simply for convenience (one at my work bench, one at my computer desk, etc). I never had an issue with it, despite the cheap price!

FWIW, my Compaq Deskpro with a Pentium II has a larger battery, it's a CR2450N. Annoyingly, I don't see what the N suffix means on that Wikipedia page, but questions on an Amazon page for this type of battery claim that the N is important for fitment somehow.

[racketboy]

Cool -- good to know -- and yes the two stack on each other.
Thinking back, it was a pain to get them out -- pretty tight fit.
If only I had read the manual about writing down BIOS settings

[Ziggy]

If only I had read the manual about writing down BIOS settings

And also wrote down the code printed on the old batteries.

So using digital calipers, you can easily get the diameter of the battery holder. But you can also measure the depth as well.

Here's a quick 5 minute rundown (if you need it) on how to use digital calipers in various ways: https://www.youtube.com/watch?v=4fBycE1dk0I

You would use the inside jaws to measure the diameter, and the depth probe to get the height.

Worth noting, when you're measuring in this kind of situation, you don't have to be dead on balls accurate (it's an industry term). Coin/button cell batteries come in a variety of sizes, but not in every millimeter increment. You really just need a "close enough" measurement to determine what type of battery it is, since there's only so many batteries it could be. The depth might be hard to get a real accurate measurement, given the springy nature of the battery holder, but an approximation will probably be enough.

[Ziggy]

I was just watching Adrian's Digital Basement (a YouTube channel) and he mentioned a really neat sounding DOS app called IDE Diag. I immediately thought of this thread. If you Google "IDE Diag" the first hit is Martin Hinner, I don't know if that's the original author or not. The second hit was the app on Archive.org. Also, this thread on Vogons that someone attached the app to (with some screen shots).

You don't need the drives to be set up correctly in the BIOS. You can load DOS from a boot disk and then load IDE Diag. It'll give you info about all of the drives in the system. You can use the top line, Geometry, to get the values you need to set in your BIOS (cylinders, heads, sectors).

Also, now that I have some vintage machines up and running, I can create a boot disk for you if you need one! I could put IDE Diag on a disk for you, too.

[racketboy]

Oh very nice! Thank you!

I'm hoping to spend some time on this project again between Thanksgiving and Christmas!

I just did get around to measuring the BIOS battery holder.
I roughly measured it at .98 inches (it's hard to know how to measure the area properly.
It seems like a 2430 battery kind fits in there -- with a single battery, it has a slight bit of room to wiggle. that coin battery measures at .95 inches
The holder takes two batteries stacked.

Thoughts?

[Ziggy]

There are many different style battery holders. Some can be larger in diameter than the battery, but a spring clip holds it in place. To remove the battery, you push it to one side and then pop it out. But the spring clip keeps tension on it so there will be no wiggle. If a battery feels loose in the holder, then it may not be the correct battery (or the holder is damaged).

What are you using to measure the holder with? If using digital calipers, there should be a button to switch between imperial and metric. Measuring in metric will be a lot easier since the batteries are coded in metric measurements.

[racketboy]

I am using a digital caliper to measure, but I switched to MM and tried it a different way to see if I could get a more accurate measure (but still unsure)
This time, it came up with 26.0 MM

I'll include a picture (although hard to see with lighting etc

2022-11-24-07.05.37.jpg (181.46 KiB) Viewed 3806 times

[Ziggy]

Ah, OK, that type of holder has one side open that you slip the battery into.

It's hard to tell from a pic, but are you sure two batteries were stacked in that holder?

Do you have the jaws of the caliper both resting against the inside wall of the holder? Again, it's hard to tell from the pic, but it sort of looks like you have one of the jaws facing the open side of the holder. I would hold the caliper perpendicular to the holder's retaining clip, so that the jaws are both hitting the inside of the holder's wall (if you aren't doing that already).

A picture to illustrate...

bat1.jpg (172.89 KiB) Viewed 3803 times

[racketboy]

Alright -- finally got back to this.
I feel like it's really hard to get a super-accurate read on it...

So I tried to measure the edge-to-edge from the top of the holder.
I got a 23.6 mm read this time, but hard to know if I've got it lined up well and/or I bump it etc.

I tried to get a better picture this time and put that sample battery in it (that had just a bit of wiggle room)

The one area with the "opening" isn't actually big enough to slide the battery in -- I think it's more to give your fingers a bit of room to pull up on them -- but even with one it, it's a pain to get in and out. The first one is really hard to get out with them both being in there.

But yes, because of the above memory, I remember clearly that there are two batteries to be in there.

2022-12-06-15.22.07.jpg (203.65 KiB) Viewed 3634 times

[Ziggy]

A 2430 battery is what's in there now (with some wiggle room)?