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Author Topic: Mounting electrolytic capacitors  (Read 6684 times)
ZL1BBW
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Posts: 402




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« on: October 31, 2012, 12:38:18 PM »

I am making a new C bank for a linear,  Has anyone an opinion on  hot glueing or super glueing capacitors a  perspex sheet?

Getting the clips is proving impossible and the caps have a pos and neg term.

Thanks
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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
KD0REQ
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« Reply #1 on: October 31, 2012, 01:30:53 PM »

I made several one-gallon tank processing lines for color film by supporting the film tanks in Plexiglas (perspex in the UK), and 24-hour epoxy was my mainstay.  since these systems were in a temperate water bath, the quick-set stuff separated, ate chemicals, and died quickly.

I haven't gone over a 1600 WVDC tension, but in my Signal-One project, I have mounted each filter cap of the B++ bank by its screw terminals on a 1/16 thick piece of epoxy/glass circuit board stock, and that to the chassis.  mount those in a plexi frame, and you ought to avoid flash-overs.  I would have barrier strips epoxied between the caps for additional flash-over protection if you're going over 3000 volts, just because.

one thing to consider about surrounding sheets of plexi across the middle of a capacitor... if it reverses or shorts and blows up real good, restricting the expansion of the cap body could lead to additional physical damage elsewhere. 
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W9GB
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« Reply #2 on: October 31, 2012, 05:41:57 PM »

WD7S offers a nice HV board for linear amplifiers.
http://home.earthlink.net/~wd7s/hv-2.htm

Very clean design, and inexpensive.
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KA4POL
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« Reply #3 on: October 31, 2012, 10:56:48 PM »

You should be fine doing this. However, don't apply to much hot glue. For horizontally mounted capacitors I use tie wraps to fix them to the board.
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K8AXW
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« Reply #4 on: November 01, 2012, 09:46:49 AM »

I have discovered the use of hot glue within the past two years.... and have concluded that hot glue is almost as good as welding!  If the caps are mounted vertically, then have no fear about them letting loose.
 
Horizontal mounting presents another problem.  Paranoia!  Provide some support.
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N8CMQ
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« Reply #5 on: November 24, 2012, 07:07:39 PM »

I am making a new C bank for a linear,  Has anyone an opinion on  hot glueing or super glueing capacitors a  perspex sheet?

Getting the clips is proving impossible and the caps have a pos and neg term.

Thanks

What is the size and shape of the caps?
Are they the can type of electrolytic?
If they have screw terminals, can you
use the bus bar style of mounting?
 
 One thing I found in high voltage supplies,
keep the high and low voltage terminals widely
separated!
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KU3X
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Posts: 144




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« Reply #6 on: November 25, 2012, 08:44:11 AM »

Did you consider laying the caps on their side and attaching them with plastic ties? Put one tie near the top and one tie near the bottom. It goes without saying you do have to drill holes in the plastic so the ties go through.
If you use long ties you could mount one cap on one side and another on the other side of the board. Now you could tie two caps to the board with one set of ties. More caps just means more ties.

Barry, KU3X

www.ku3x.net
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KB4QAA
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« Reply #7 on: November 26, 2012, 07:38:34 AM »

http://www.mouser.com/catalog/catalogusd/645/885.pdf

capacitor mounting hardware is readily available.  Here is just one page of Cornell Dubilier parts from the Mouser catalog.
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K8AXW
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« Reply #8 on: November 26, 2012, 09:23:52 AM »

QAA:  Excellent answer! Problem solved!  Unless there is an accessability problem.

Which in that case.... if push comes to shove, these clamps can easily be fabricated by hand tools using aluminum strips for the band and short pieces for feet fastened to the bands with pop rivets. (head on the inside of the ring).  Use the link provided by QAA as a guide.

I used a similar process to fabricate beam boom support wire clamps from stainless steel.  (Hy-Gain didn't use stainless steel at this time) 
« Last Edit: November 26, 2012, 09:32:45 AM by K8AXW » Logged
ZL1BBW
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« Reply #9 on: November 27, 2012, 10:42:42 AM »

Hi , Thanks for all the info, had a look at the mouser site, but at over 6 bucks for a clip, it becomes a bit expensive :-).

Am just going through the process of getting my old 2 x 4-400 linear back on the air, so hopefully will buy me some time before I start making the new linear.

I have found 2 big caps that I bought a while ago, they are 235 UF at 2500 volts dc each, so once I have the old HT unit running I will put those across the HT and see how they perform.

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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
N7EKU
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Posts: 112




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« Reply #10 on: November 28, 2012, 10:38:28 PM »

Hi,

Hot glue is OK, but is not that tough and the bond is not always great (depends on the material).  But for a lot of purposes it is great -- fast drying, easy to remove, and pretty safe and non-toxic.

I've never found super glue to be that great.  It was basically designed as a very thin layer bonding agent which works great for that purpose (like bonding two smooth squares of steel together like in the commercial), but I rarely come across that situation when I'm gluing!  Also, it will damage the surface of many plastics.  A better use is detecting fingerprints with its vapor!

I'm surprised that no one mentioned silicone sealant.  This great for homebrew.  It's waterproof, quite strong, very long lasting, easy to clean up after, and comes in various colors.  Dried sealant can be removed with a bit of work (elbow grease and tough fingernails).

A hint for silicone:  after you open the tube and use some, put it in a freezer thickness ziplock bag with the air squeezed out and keep the whole thing in your 'fridge.  It will last for ages and not harden in the tube.  Maybe put it in two ziplock bags for the xyl's approval hihi!

73,


Mark /N7EKU
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K8AXW
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« Reply #11 on: November 29, 2012, 07:59:37 AM »

DAB:  I'm having a bad day understanding some things.  Sorry. 

As I understand (?) you're in the process of getting your old 2 X 4-400 amp back online.  This power supply you're putting together..... is it for the 4-400 amp?

When you say "across the HT" do you mean the HV (High Voltage)

Two caps at 235ufd @ 2500v in series will give you approximately 117ufd @ 5,000v.  With a 4-400 amp you need only about 40ufd of capacitance..... maximum! 

Or is this power supply you're building for the NEW amplifier?

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KD0REQ
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« Reply #12 on: November 29, 2012, 04:01:01 PM »

AXW has a really good concern, that's way the hay too many joules of storage to be complacent about.  hope to heck you don't have a filter choke in there, that startup surge would bend train rails, and you could sell tickets to the smoke test, assuming the crowd was behind safe glass partitions.
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ZL1BBW
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Posts: 402




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« Reply #13 on: November 30, 2012, 12:18:21 AM »

Yep well the PSU I am working on at the moment is for the old 2 x 4-400 amp, and I am having enough problems with inrush current already.  I replaced the transformer with a newer one 750 0 750 through a doubler into about 30uF.  Anyway after a bit of trial and error , no smoke, I found that a 100 watt bulb is just right for limiting the inrush on switch on.  I always run  bleeder currents and even with that I am still getting a very nice steady 3200volts.

As for the NEW amp, well, that is a little way off, but yep the 2 big caps would be a bucket load of capacity for sure.  But luckily I also obtained a large variac weighs about 30kgs, so intention is to use that to slowly wind up the HT (High Tension) or as our lecturers oft referred to it as Hurting Tension.

AS for the smoke test, well that brings back memories of a very overloaded marine HF Tx giving up the ghost and burning out the mode switch at sea...........   so ended up hardwiring it into cw only and that is how it lasted till we got to port again.

Am still mulling over what to use in the new amp, have a good few 4-400 valves so nil cost there, but they are big and filament current hungry bottles, so the thoughts of splashing out on a 8877 has been running around in my mind, but that isbest part of a grand plus in NZ$ so could use that to get a decent cubex quad.

My end aim... is to be able to run a full 1000 watts of output on any mode from 160 - 10, so bit by bit I will get there, its sort of a bucket list thingy.
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ex MN Radio Officer, Portishead Radio GKA, BT Radio Amateur Morse Tester.  Licensed as G3YCP ZL1DAB, now taken over my father (sk) call as ZL1BBW.
K8AXW
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Posts: 3910




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« Reply #14 on: December 01, 2012, 09:16:12 AM »

I wouldn't use those big caps.
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