Mounting Radial electrolytic capacitors Axially? - Page 1
Forum section: electronics / projects

author: h1386343
author_rank: Regular Contributor
timestamp: January 20, 2014, 05:49:46 pm
content: Hi guys, quick question with regards to replacing failed axial electrolytic capacitors in test equipment with newer, radial ones:All specs being equal (capacitance, voltage rating etc...)how would you mount the replacement radial capacitor?1: mount the capacitor centrally and have equal length + and - leads going to the original PCB holes2: mount the capacitors + lead as close to the PCB hole as possible and have a long - lead to the other hole3: mount the capacitors - lead as close to the PCB hole as possible and have a long + lead to the other holeI was leaning towards option 2, with the - lead running across the board, this would reduce the possibility of the + lead touching anything (lead would obviously be insulated either way) but i wasn't sure if having an extra long ground lead would increase susceptibility to interference or anything? increase the inductance of the capacitor and increase ripple current?The capacitors that need replacing are in the power supply section of an old 'scope if that has any influence on it?Look forward to getting some replys. I'm fairly sure that theres not going to be too much in it, other than from a best practices point of view, and no long + leads running across the board!

author: SeanB
author_rank: Super Contributor
timestamp: January 20, 2014, 06:15:54 pm
content: As the replacements are likely to be a lower ESR and a smaller size just use 2 or 3, and physically attach the capacitor to the board if it is large ( use either thick superglue or acetoxy free silicone between the capacitor and the board) and if it had some mounts then add a sleeve to get it to the right diameter to fit the mount again.

author: h1386343
author_rank: Regular Contributor
timestamp: January 20, 2014, 07:13:13 pm
content: yeah the replacements i have are like 1/2 the size of the originals for the same capacitance voltage rating, thats what got me thinking about how to mount them.With the originals being mounted axially there is a gap of almost 11cm between the mounting holes. This would mean that for either option 2 or 3 i would end up with a long lead across the board. I guess if it was insulated correctly it wouldn't matter which lead it was?the capacitors are secured to the board with zip ties so ill just replace them too.What do you normally use to attach larger components to the board? I had a look on Farnell for silicone adhesives but i didn't want to pay for a whole tube if i'm only going to use it for this one repair.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: January 20, 2014, 07:15:34 pm
content: I use hot glue. Position depends on the space and mechanics. For a really long span I might bend one lead at 90 degrees and install the part sideway on the board right at one hole. A wire then goes from the other lead to the far away hole.

author: SeanB
author_rank: Super Contributor
timestamp: January 21, 2014, 06:54:44 pm
content: Thick gap filler superglue ( the cheap one) works fine for this, though you will find the white bloom from it a bit hard to clean off.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 21, 2014, 11:40:02 pm
content: I've done this before..http://webpages.charter.net/dawill/tmoranwms/Elec_Scope2_lg.jpgOne way to do it... not the best for mechanical support, but some goop would handle that.Tim