400 K Floppy Drive Repair Components

lundpk

lundpk

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My retro rebuilding club at my college is starting to work on some projects - one is a Sony 400K floppy drive. I started looking up components on Mouser's website, however I am now seeing issues with the availablity. The message "Mouser does not presently sell this product in your region." is coming up on the website for basic component. JDW did a nice job of putting together a component list.

Macintosh 400k SONY Floppy Drive Electrolytic Capacitors

Big PCB:

6pcs of 47uF 16V, D=6.5mm, H=8mm, Lead Spacing=2.5mm (Mouser: UTT1C470MDD1TP)

4pcs of 22uF 16V, D=5.1mm, H=8mm, Lead Spacing=2.5mm (Mouser: UPW1C220MDD6)

Small PCB:

4pcs of 10uf 16v, D=4.2mm, H=7mm, Lead Spacing=2mm (Mouser: UTT1C100MDD1TP)

6pcs of 10uf 35v, D=5.15mm, H=6.2mm, Lead Spacing=2mm (Mouser: UMV1V100MFD1TP)

2pcs of 0.47uF 50V (could be 16V), D=4.2mm, H=6.2mm, Lead Spacing=2mm (Mouser: USV1HR47MFD)

2pcs of 0.22uF 50V (could be 16V), D=4.2mm, H=5.8mm, Lead Spacing=2mm (Mouser: UMV1HR22MFD)

2pcs of 1uF 50V, D=4.2mm, H=7.5mm, Lead Spacing=2mm (Mouser: UTT1H010MDD)

=================

Are there other sources of components at this time?

Thanks,

Perry
 
JDW

JDW

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Professor Lund,

Great to see you posting here on TinkerDifferent!

I was trying to swap out capacitors in my two Carts after reading your post, but suddenly the entire website shutdown...

1759406835194.png


I guess I will need to wait until tomorrow.

Tariffs have wreaked havoc across all my Mouser Carts, I must say. It's very frustrating.
 
JDW

JDW

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The site is working today, but even though I have the site set to the Japan region (where I live), I am getting the same message...

1759441099896.png


That indicates it may not be sold anywhere, which is very odd.

Swapping out the caps is going to take time because the ones in my cart originally were the best caps available at the time. Now I am finding inferior ones. They will work, but have higher ESR. For example, consider the specs of one of the 22uF caps in my 400K Drive OA-D34V-22 Cart, with ESR of 270m-Ohms and 350mA Ripple Current:


An in-stock 22uF cap with the same physical size and lead spacing and capacitance has higher ESR, as evidenced by the tiny 50mA Ripple Current:


Sometimes choosing a higher voltage cap will reduce the ESR, but there is an upward limit to that because there will come a point when you won't be able to find a cap in the physical size you need, and if the cap is too big, it won't fit. That's why it takes time to find good replacements. You need caps that fit into the space on the PCB, have the right lead spacing, and also have good specifications (105°C, low ESR where possible, etc.).

⚠️ By the way, in your opening post, there is an ERROR in regards to the QTY of 0.47uF capacitors. You wrote 2pcs, but in fact you only need 1pc on the Small PCB.

Because I need to get read to go to work now, I will need to examine this later.
 
JDW

JDW

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Professor Lund,

I've spent a number of hours on this, both yesterday and today. This issue has become really complicated due to Mouser having killed off the right caps, so this post is long and messy as a result.


Just to correct and clarify your opening post, the Big PCB on the 400K drive only requires HALF the quantity of caps you mentioned (for a single 400K drive), so the following is correct:

Big PCB:

3pcs of 47uF (stock specs: 16V, D=6.5mm, H=8mm, Lead Spacing=2.0mm or 2.5mm)

2pcs of 22uF (stock specs: 16V, D=5.1mm, H=8mm, Lead Spacing=2.0mm or 2.5mm)

That applies to both Carts listed under my video — two carts because 400K drive types and PCBs differ...

400K_Floppy_Controller_01.JPG 400K_Floppy_Controller_05.JPG


The capacitor-related differences between the two 400K drive types appear on the Small PCB, and the 0.22uF in an aluminum electrolytic type is nowhere to be found on Mouser as of today.

I am, however, able to find in-stock 0.22uF caps in solid Tantalum LEADED form here:


The big issue is that the HEIGHT of the stock cap is 5.8mm or so. Those solid leaded Tantalum caps are 7mm to 7.11mm tall. By far, they are the BETTER cap though because they won't need to be replaced. And although I have no idea if the working voltage is 5V or 12.5V across that cap, even if it is 12.5V, the solid leaded Tantalum caps linked above are rated for more than double that working voltage (35V or 50V) which means you're safe.

So the question is, can you buy the solid tantalum cap and make it fit? Probably because the other caps on that SMALL PCB are 7.0mm.

For now, this is the one I will pick as it is D=4.4mm:

But here's the issue. The stock cap LEAD SPACING is 1.5mm, and that tantalum cap is 2.54mm. That means the cap would stand up on its legs, further increasing its height off the PCB, which I think may pose a problem. But perhaps you could lay down that cap on its side to make it fit, because it is not adjacent to other caps in the area.

That very well might work, but perhaps ONLY on this PCB type...

400K_SmallPCB_Type1.jpg

⚠️ But it doesn't appear possible to "lay down the cap on its side" if you have the following Small PCB type...

400K_SmallPCB_Type2.jpg

Nevertheless, I have swapped in that tantalum cap on both of my SMALL PCB Mouser Carts, because that's all we have!


The 1uF capacitor I had chosen in my carts previously was the best. 20mA Ripple current and low ESR. All the aluminum electrolytic caps in the physical size we need are only 10mA Ripple current, which means about double the ESR...


However, if we do with this 1uF cap as I did with the 0.22uF cap and go with leaded Solid Tantalum (which again has enough voltage headroom to be safe), this one would be my pick...


I've added that to my two Carts. And because it is isolated from other caps, you MIGHT be able to lay it down on its side to make it fit. This is speculation on my part, but it's the best I can do, since I don't have that cap.


Both of my Mouser Carts are now EXACTLY THE SAME. So I will at some point eliminate one and update my video description to reflect that. Both are complete with no out-of-stock caps as of this writing. You can buy either one.

• Mouser Cart for newer OA-D34V-22: https://bit.ly/3dl56B9
• Mouser Cart for older OA-D34: https://bit.ly/2zSpzyy

10/09/2025 EDIT: Both Carts are now exactly the same.
 
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lundpk

lundpk

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James,

Your deddication to the retro electronics folks here is outstanding. Thank you for the several hours of work you put into this project.
Do you believe the other capacitors will ever be available again?

Both my external 400 K drives have not been disassembled to see which board I have. I will do that on Monday to select the correct components from your cart choices.

Perry
 
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JDW

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I believe strongly in helping out my fellow vintage Mac enthusiasts as much as humanly possible, in large part because I have the “do to others as you would have them do to you“ philosophy. I myself have a lot of help through the years, so when I have the ability to help someone else, I want to do my part.

I also try to get answers for people in a timely manner because I myself don’t like to be kept waiting for many days or weeks. I had hoped to get back to you in 24 hours, but the complexity of the problem caused it to be two days, so I apologize for that.

In answer to your question about whether the perfectly sized electrolytic capacitors that I had selected previously in my Carts will become available again, sadly, due to tariffs and a lot of craziness that’s been going on this year, I really have no idea. Best to assume they won’t be in stock again.

With that said, the capacitors I selected yesterday are the best I could find at this time.
 
JDW

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Capacitors for the LARGE PCB are the same across all 400K drive types. Only the SMALL PCB have differences.

Your photo of the SMALL PCB matches my photo here...

400K_SmallPCB_Type1.jpg

That is a good thing because I am worried about the other version SMALL PCB where you must put one of the capacitors on the left side, and there's no space to lay that capacitor down on its side. But you don't need to worry about that because your small PCB has only 2 caps on the side. So all should be well.

Both of my Mouser Carts are now EXACTLY THE SAME. So I will at some point eliminate one and update my video description to reflect that. Both are complete with no out-of-stock caps as of this writing. You can buy either one.

• Mouser Cart for newer OA-D34V-22: https://bit.ly/3dl56B9
• Mouser Cart for older OA-D34: https://bit.ly/2zSpzyy

Both carts include caps for the BIG and SMALL PCBs.
 
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JDW

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The reason I had two different Carts before is because one version of the Small PCB had space for physically larger capacitors, which also have better specs. So I took advantage of that by creating a special Cart for that version which had wider and better caps. But those caps are out of stock and it doesn't look like they will ever come back. So that's why I revamped both carts the other day, and now both carts are the same.

10/09/2025 EDIT: Because both carts are the same, I updated my YouTube video's description to reflect that.
 
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lundpk

lundpk

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JDW said:
Capacitors for the LARGE PCB are the same across all 400K drive types. Only the SMALL PCB have differences.

Your photo of the SMALL PCB matches my photo here...

View attachment 23575

That is a good thing because I am worried about the other version SMALL PCB where you must put one of the capacitors on the left side, and there's no space to lay that capacitor down on its side. But you don't need to worry about that because your small PCB has only 2 caps on the side. So all should be well.

Both of my Mouser Carts are now EXACTLY THE SAME. So I will at some point eliminate one and update my video description to reflect that. Both are complete with no out-of-stock caps as of this writing. You can buy either one.

• Mouser Cart for newer OA-D34V-22: https://bit.ly/3dl56B9
• Mouser Cart for older OA-D34: https://bit.ly/2zSpzyy

Both carts include caps for the BIG and SMALL PCBs.
Click to expand...
It appears that my drive is OA-D34 unit like your unit I was viewing in your tear down and renovation video.
 
lundpk

lundpk

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Dec 16, 2023
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New Ulm, MN
blc.edu
JDW said:
The reason I had two different Carts before is because one version of the Small PCB had space for physically larger capacitors, which also have better specs. So I took advantage of that by creating a special Cart for that version which had wider and better caps. But those caps are out of stock and it doesn't look like they will ever come back. So that's why I revamped both carts the other day, and now both carts are the same.
Click to expand...
Alright James.

I am excited to report I have made my first Mouser order. :cool:

I asked students to watch your 400K drive video to prepare for the work ahead. Excited to see how things go.
I have 2 400K external drives, and I can test the results on my 512K restored and recapped classic Mac. :)
 
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