[R-390] Filter cap replacement question

[Glenn Little WB4UIV]

A word of caution on the use of RTV. It comes in at least two types. If it 
smells of acetic acid, do not us it around anything metallic that you do 
not want to corrode. I learned this the hard way. I potted the VCO in my 
first GLB synthesizer just as the instructions said. About two years later 
it quit. When I troubleshot the problem, I found all the copper leads in 
the potted area were dissolved. The RTV when it cures, by the moisture in 
the air, releases acetic acid. This dissolved the copper.

There is another type of RTV that is listed as "Oxygen sensor safe". This 
is available at auto parts stores. This type is also available from 
industrial supply houses. This cures with an alcohol and does not cause any 
issues with the electronics.

73
Glenn
WB4UIV



At 11:29 AM 08/16/05, Craig C. Heaton wrote:
>I ordered from Mouser, Xicon 140-XRL350V33 and 140-XRL350V47. These are
>radial lead electrolytics. A dremel tool with a cut-off disk made a quick
>job of neatly removing the lip on the old cans. Apply some heat with a
>propane torch to loosen the uckumpucky and pull out the old guts. Clean the
>inside of the old cans with some type of solvent. Drill and tap the pins of
>the base. I think I used 4-40 stainless screws with solder lugs. For the can
>with three 33uF caps, I stacked one on top of two, had to lengthen the leads
>on the top cap. A little heat shrink on the leads, some RTV to hold things
>in place, slide the cover back on with a dab of super glue.
>
>Looks good, lasts long time.
>
>Craig,
>
>-----Original Message-----
>From: r-390-bounces at mailman.qth.net
>[mailto:r-390-bounces at mailman.qth.net]On Behalf Of Barry
>Sent: Tuesday, August 16, 2005 6:19 AM
>To: R-390 HF Receiver List
>Subject: [R-390] Filter cap replacement question
>
>
>For you guys who are restuffing your R390A's electrolytics, which caps are
>you using?  I ordered some from Mouser with the intent of simply installing
>them "bare" through the holes in the octal sockets.  Sadly, the octal
>sockets in this AF module, though, don't have through hole style sockets;
>therefore, I'm planning on using an octal plug.  I have some old cans from
>another set I've gutted, but these caps are just about 0.010" in diameter
>too large to stuff three of them in the can so I was wondering where you are
>getting caps small enough to fit three inside the cans.
>
>I have some old burned-out octal tubes and their bases are a perfect press
>fit in the old cans so if I can find small enough caps, this should be a
>cake-walk.
>
>Thanks in advance,
>
>Barry - N4BUQ
>
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