[Bosk]

I'm planning on upgrading the electrolytics in the power sections of my DAC-AH and t-amp, and I'd ideally like to replace them with higher value uF (larger size) versions.
Eg. the 2200uF caps in the DAC-AH I was thinking of swapping for some 4700uF or 8200uF caps depending on what I can get to fit.

In doing this, I may not have room for slightly larger caps unless I bend them outward from the components nearby so that they will fit - in which case the bases of the caps will probably not be making contact with the PCB.

Does this actually matter? I mean does it matter if the caps are 'suspended in mid air' supported only by the leads soldered to the PCB?

 

[tomb]

Quote:

Originally Posted by Bosk /img/forum/go_quote.gif I'm planning on upgrading the electrolytics in the power sections of my DAC-AH and t-amp, and I'd ideally like to replace them with higher value uF (larger size) versions. Eg. the 2200uF caps in the DAC-AH I was thinking of swapping for some 4700uF or 8200uF caps depending on what I can get to fit. In doing this, I may not have room for slightly larger caps unless I bend them outward from the components nearby so that they will fit - in which case the bases of the caps will probably not be making contact with the PCB. Does this actually matter? I mean does it matter if the caps are 'suspended in mid air' supported only by the leads soldered to the PCB?

Yes, it matters ... but it may not be audible and could be trivial.

The electrolyte is capable of picking up vibrations, which could affect the cap's performance. You'll note that the better quality electrolytic capacitors have a rubber pad on the bottom for cushioning. There's not much point in air-wiring them if they have that pad. Does that mean you shouldn't do it? No, we all do it from time-to-time. Just be aware that it may not be optimum.

 

[m1abrams]

Also do not forget that those long leads make great antennas.

Also bigger is not always better, I do not know much about the amp in question however make sure that the amp and dac can even benefit from a larger cap.

 

[deltaydeltax]

I've had large electrolytic caps vibrate inside sub-woofer cabinets. The vibration actually made its way out of the cab and listeners were able to hear it. So, I glued them down in their place.

 

[linuxworks]

seems to be a 'last 5%' kind of thing.

most gear does not 'secure' the caps to the board but I've seen some that use wire ties to keep larger caps in place.

sometimes I do see 'thread lock' stuff used to also glue them down.

does all gear do this? no. all high end gear does this? nope, not even all 'high end'.

I wouldn't worry about it, really. don't make them *many inches* but keep them short and you should be fine.

 

[tangent]

When you see caps glued to a PCB in a piece of commercial equipment, you can bet it's because they were more worried about UPS than THD. Commercial testing procedures often include a shaker table step...the caps that get ripped off the board by the vibrations get glued down, lest the product arrive DOA after a particularly rough time through the shipping system.

For DIY purposes, I'd worry more about RFI pick-up and increased ESR and ESL when air-wiring caps, than vibration issues. Part of the reason you use a bigger cap is to reduce ESR and ESL, so why then put more Rs and Ls in series with it by using too much wire?

 

[linuxworks]

UPS the shipping company or UPS the power supply?

yeah, ok, the shipping company. my computer power supply doesn't bounce boxes around nearly as much.

 

[aos]

Quote:

Part of the reason you use a bigger cap is to reduce ESR and ESL, so why then put more Rs and Ls in series with it by using too much wire?

I agree. However I do sometimes mount the through-hole capacitors horizontally. Usually when there's no vertical room in a tight space or when I screw up board layout and have the cap encroaching on some other part's space. Depending on the cap's purpose, the extra R/L doesn't really matter. If it does, you should be using SMD in the first place.

 

[Nemo de Monet]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif . You'll note that the better quality electrolytic capacitors have a rubber pad on the bottom for cushioning. There's not much point in air-wiring them if they have that pad.

Are you sure that's what the rubber's for? I always thought it was to raise the bottom of the cap off the board, so it could be wave-soldered safely.

 

[BrianDonegan]

Everything you need to know (it says SMT, but covers TH as well):

http://www.panasonic.com/industrial/...um_app_dne.pdf

 

[aos]

Interesting app note. Although the only thing related to the issue I could find is:

"Be careful of the sympathetic vibration after mounting on the board, mechanical stress will adversely affect the mounting strength and electrical characteristics. Use reinforcements like adhesive for large size products when capacitor is mounted horizontally on a vertically positioned borad (sic)".

 

[tomb]

Quote:

Originally Posted by Nemo de Monet /img/forum/go_quote.gif Are you sure that's what the rubber's for? I always thought it was to raise the bottom of the cap off the board, so it could be wave-soldered safely.

Well, I could've sworn I read it somewhere, but after doing a bit of research, it appears that we're both wrong. The rubber is there to provide an expansive seal for solvent/cleaning resistance.

 

[digger945]

I like mine jacked up. It makes it easier to vacuum

.

As you can see, I'm behind on my vacuuming.