Leaking capacitor?

[JoeG]

Being a newbie in electronics, I've never encountered a leaking capacitor. Attached are some photos of a floppy drive interface cable for a CompuAdd laptop that I acquired several months ago. The cable has a capacitor attached to some of the pins on the cable connector.

The floppy drive has never worked. I checked it before, and thought that the "white stuff" under the capacitor was a glue to hold it down to the housing for the cable connector. Since then, I've acquired a replacement floppy drive for the unit. I started the process of replacing the drive today and encountered the capacitor and stopped.

But now that I've learned a little more than when I first looked at the capacitor, it looks like it leaked to me. Being that I've never seen one up close, I don't know. So I pulled the capacitor away from the "white stuff" to see if I could see a burst in the capacitor.

A few questions:
1) Does it look like glue, or a leaky capacitor to you?
2) Is there a test I can perform to see if it is in fact a leaky capacitor such as using white vinegar or a baking soda mix (not both since that will cause a reaction on its own) to see if there's a chemical reaction?

Thank you

Joe

[Steve Simpkin]

That does not look like electrolyte leaking from a capacitor to me. This is an example of a leaking capacitor.
https://i.stack.imgur.com/73Ww9.jpg

Is the white stuff wet or sticky?
Or is it hard like dried glue?

[nickapos]

(09-05-2023 10:08 PM)JoeG Wrote:  Being a newbie in electronics, I've never encountered a leaking capacitor. Attached are some photos of a floppy drive interface cable for a CompuAdd laptop that I acquired several months ago. The cable has a capacitor attached to some of the pins on the cable connector.

The floppy drive has never worked. I checked it before, and thought that the "white stuff" under the capacitor was a glue to hold it down to the housing for the cable connector. Since then, I've acquired a replacement floppy drive for the unit. I started the process of replacing the drive today and encountered the capacitor and stopped.

But now that I've learned a little more than when I first looked at the capacitor, it looks like it leaked to me. Being that I've never seen one up close, I don't know. So I pulled the capacitor away from the "white stuff" to see if I could see a burst in the capacitor.

A few questions:
1) Does it look like glue, or a leaky capacitor to you?
2) Is there a test I can perform to see if it is in fact a leaky capacitor such as using white vinegar or a baking soda mix (not both since that will cause a reaction on its own) to see if there's a chemical reaction?

Thank you

Joe

Looks like glue to me.

[JoeG]

It has the consistency of old Elmer's glue that hasn't been used in a while, kind of like silicone.

Joe

[Steve Simpkin]

(09-05-2023 10:44 PM)JoeG Wrote:  It has the consistency of old Elmer's glue that hasn't been used in a while, kind of like silicone.

Joe

It probably is silicone glue/sealant used to keep the capacitor from moving.
https://www.icrfq.net/pcb-glue/

[Jeff_Birt]

That looks like an adhesive to hold the cap in place. The cap will leak where the leads exit and this area will usually look a little wet/crusty and will smell like fish when heated.

The electrolyte in the capacitor is acidic. You want to neutralize it with a mild alkaline solution like a strong lye soap/cleanser.

[JoeG]

Thank you!

I removed the old floppy drive from the laptap, and installed a replacement. Notice I said "replacement" and not "new". The floppy is a Epson SMD-1000 3.5" drive. The replacement doesn't do anything different than the first one did, which is not read or write to a floppy.

I found this on the web, which describes the symptoms my floppy drives are having:
http://asknotes.com/2021/03/15/fixing-ep...isk-drive/

So I opened up the floppy drive I removed, and sure enough the same capacitor leaked. And yes Jeff, heating it up to remove it did smell like fish. I ordered some replacements. I didn't remove the smaller capacitor because even under binocular type of glasses it looks nice and clean. And, it's really tough to access. But if the drive doesn't work after replacing the capacitor, I can replace the other one as well. Even then, the problem might be more than just the capacitor.

If I can get this laptop to work with a floppy drive, I can load Windows 3.1 on it like it originally had from the factory. I'll still need to find a reasonably priced 9 pin serial mouse for it as well.

Joe

[ijabbott]

(09-05-2023 10:44 PM)JoeG Wrote:  It has the consistency of old Elmer's glue that hasn't been used in a while, kind of like silicone.

It will be electronics grade RTV Silicone. Often used to stick electrolytic capacitors to each other or another surface to mechanically stabilize them.

[Bushcat]

(09-06-2023 08:09 PM)JoeG Wrote:  I didn't remove the smaller capacitor because even under binocular type of glasses it looks nice and clean. And, it's really tough to access. But if the drive doesn't work after replacing the capacitor, I can replace the other one as well.

Electrolytics are lifed items. Whether they've leaked or not, and if it's no hassle, it's always a good idea to replace capacitors older than, say, 15-20 years. Very roughly, useful lifespan for smaller electrolytics (up to around 8mm diameter) is around 5000 operating hours (210 days) at max. rated temperature (105C in this case), but doubles for every 10C below that. Around 30 years ago, there were a lot of fake electrolytics with bad electrolytes in the can, so I'd swap them out as a matter of principle if I had replacements laying around.

They can also drop way out of spec if they've not been used for a while. Simply using the equipment resurrects them most of the time.

Edit: changed "210" to "105C". Doh!