Capacitor glue question

[Numistrek09]

Ok, i'm replacing several caps that were originally glued to the board. Do i need to glue down the new caps as well, or can they sit free? And if i do need to glue, what glue to use and what should i get the old stuff off with?

 

[Monty_]

There's really no technical reason to glue capacitors to the circuit board; perhaps it was originally done to reduce shock and vibration damage from shipping long distances.

Off the top, I think any chemically compatible glue that's temperature stable can be used; it ain't NASA so likely even white glue would do. As for the old glue, just scrape carefully and clean.

 

[nashvillebill]

I glue caps on guitar/bass amps since these see lots of vibration while playing, as well as rough handling (ever seen a band load-out at 2 in the morning...).

On home audio stuff, I glue the largest caps down but don't typically glue anything else.

I just use hot melt glue. I'm sure there's better stuff but hey at least it's not silicone glue (don't want the acetone that's outgassed).

 

[TerryO]

I assemble my diy crossovers (usually) on prefboard, so I use wire ties and a dab of hot glue. It keeps things from vibrating or slipping around.

Best Regards,
TerryO

 

[BinaryMike]

There's really no technical reason to glue capacitors to the circuit board; perhaps it was originally done to reduce shock and vibration damage from shipping long distances.

Right! Capacitor leads will definitely fail due to fatigue from shipping vibration.

Avoid silicon-based adhesives and sealants in electronics; they liberate corrosive gas.

 

[33&athird]

Also keep in mind that some caps vibrate a little bit when cycling, on very delicate circuits glue can be used to make the capacitors more stable long-term. In most consumer electronics, it's not needed at all.

I've also heard that they would glue the caps on the board so they could solder it on the underside without the part falling out.

 

[merrylander]

Exactly, when the boards are wave soldered they need to keep the big caps in place. If you look carefully you will see that smaller parts have the ends of the leads bent over to keep them in place.

 

[Numistrek09]

So just plain old craft hot glue? I've got a few bags of it, but it doesn't say what it's made out of.

 

[Wazz]

Your craft glue should be OK. Just try to confine it to the capacitor and the board. Just use enough, not too much and have a mess! Silicone or RTV sealants have been used in electronics, I have seen it. There are versions of it now that are made without the weak acids in the compound that were maybe resulting in corrosion on components. I know for a fact that it is approved to use in the equipment that is in aerospace electronics, darn if I can remember the part number, but the undesireable sealants have a definite sort of vinegar smell that the safe stuff is lacking. There are specifications for using it by major manufacturers of aircraft electronics. But hot glue is alot quicker to use. Perhaps something like GC service cement could be used in some cases, it is for electronics repairs.

 

[Tom Bavis]

Electronic RTV does not give off the acetic acid that can cause corrosion. Don't use aquarium caulk or bathtub caulk...

 

[benb]

Right! Capacitor leads will definitely fail due to fatigue from shipping vibration.

It's probably not the leads so much as the solder joints. Solder does fine at holding very small, lightweight components, but on larger ones the joints can go bad and come loose with big components vibrating, such as the big poly caps and power resistors in speaker crossovers. Gluing or tying them down will keep things from going wrong.

I've seen this in PC power supplies, the taller electrolytics are often glued to the board on the component side.

 

[BinaryMike]

It's probably not the leads so much as the solder joints. Solder does fine at holding very small, lightweight components, but on larger ones the joints can go bad and come loose with big components vibrating, such as the big poly caps and power resistors in speaker crossovers. Gluing or tying them down will keep things from going wrong.

I've seen this in PC power supplies, the taller electrolytics are often glued to the board on the component side.

I've seen capacitor lead failure from metal fatigue firsthand several times. The remaining lead is still securely soldered in the PCB. It looks like a little flat-topped stump, sheared off near the top surface of the board, but without any tool marks.

 

[minkybut]

Yes Yes, I know this an old thread. I'm new to this but want to fix my Yamaha c45 pre myself. I took the cover off and round the two big caps there is the orange looking glue..all over the board and some other little gizmos on the board. I see there is a small bit of green corrosion on some of the doodad leeds. Is this something I can clean-up? Am I going to get electrocuted if I do this myself? How do I kill the corrosion?

 

[glen65]

Yes Yes, I know this an old thread. I'm new to this but want to fix my Yamaha c45 pre myself. I took the cover off and round the two big caps there is the orange looking glue..all over the board and some other little gizmos on the board. I see there is a small bit of green corrosion on some of the doodad leeds. Is this something I can clean-up? Am I going to get electrocuted if I do this myself? How do I kill the corrosion?

I assume youre talking about this..

If thats the case, it will involve removing some of the components, cleaning
off the glue (not an easy job), then replacing them with new ones.

 

[minkybut]

WOW, when did you get into my house and take my Yammi apart? Mine looks exactly like that. I see you have some green corrosion also. Sounds like a job for my audio guy or is it something that is not needed?

 

[minkybut]

I just got my Yamaha yesterday. Should I just hose down the pots to clear up the scratchiness controls and let the glue thing ride?

 

[glen65]

WOW, when did you get into my house and take my Yammi apart? Mine looks exactly like that.
I see you have some green corrosion also. Sounds like a job for my audio guy or is it something that is not needed?

You're not the first, the pic is from someone else who has the same unit.
As to your question, yes it will need to be dealt with. Some of the components
need to be taken out, so that the glue can be removed. The components such
as capacitors should be replaced with new ones.

 

[glen65]

I just got my Yamaha yesterday. Should I just hose down the pots to clear up the scratchiness controls and let the glue thing ride?

No, the glue needs to be removed. That area can become conductive and cause real problems.

 

[roger2]

Glue and its removal has been discussed many times at AK, particularly in the Sansui forum. AK Advanced Search or Google search of AK will give you all the info you need.