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<DIV>I had this problem wit a machine in service in the 70's. It was one
of the caps that leaked and ate the board. I do not think this is an age
factor or environment. It just happens. I think that if I had done
inspections rather than wait it would have been caught.</DIV>
<DIV> </DIV>
<DIV>As they say, s--- happens!</DIV>
<DIV> </DIV>
<DIV>Chris Hill</DIV>
<DIV> </DIV>
<DIV>
<DIV>In a message dated 11/12/2012 1:56:46 P.M. Eastern Standard Time,
leodham@centurylink.net writes:</DIV>
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<P>Hi Don & Park,</P>
<P> </P>
<P>Yeah I wondered a little bit about why/how such a big mess was made, too.
This particular colortec may have been exposed to extreme temperature changes
over a period of time in an uncontrolled storage situation.</P>
<P>I'm thinking it was one of the spare pieces that came from out back of the
Winston-Salem cat house guy. The fellow's name escapes me, but I do
remember all those cats running around all inside the
building. There were a couple tractor trailers full
of equipment & various parts-pieces parked out back and this
colortec came from one of those vans I'm pretty sure.</P>
<P>Maybe the 15-20 degree freezing temperatures made them pop, or the
120 degrees inside heat in the summer.</P>
<P> </P>
<P>The last batch of those exact OEM type caps I purchased was at
Sky Craft in Florida last Feb. after the Orlando hamfest. $4.
dollars each for 270 uf.</P>
<P> </P>
<P>I shoulda bought more! haha.</P>
<P> </P>
<P>At this late date, I really want to stay as true to original as possible.
Those oem's have lasted for 40+- yrs, a tall order for any electrolytic. Many
years ago attending the engineering program at NE State Tech, I was
taught that electrolytics have a shelf life; ie., they will go bad new
sitting on the shelf after enough time passes and the electrolyte dries out
enough. The sealed 'wet' caps were an attempt at stabilizing and extending the
useable life by keeping the electrolyte stable(from drying out).</P>
<P> </P>
<P>Seems that idea worked pretty good!</P>
<P> </P>
<P>Larry Odham</P>
<P> </P>
<P>Quad Tape Transfer</P>
<P><A title=http://www.quadtapexfer.com/
href="http://www.quadtapexfer.com/">www.QUADTAPEXFER.com</A></P>
<P><BR><BR> </P>
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<DIV>Hi Larry:<BR><BR>I've seen a few failures like this, but not this
bad!!!</DIV>
<DIV> </DIV>
<DIV>Most of the tantalums that Ampex used in the quad era were mil-spec,
hermetically sealed units, and they almost never go bad. However, these
particular ones are wet tantalums which are not hermetically sealed.
Since these are simply filters across the power supply busses, you could
replace them with modern-day electrolytics which are small enough
these days to fit in the space available. However, if you insist on the
"original" parts, they are still available from suppliers like Avnet or Arrow,
but you'll pay $40 to $50 EACH for them. I did spot a few on eBay for
$15/ea....a real deal!!!</DIV>
<DIV> </DIV>
<DIV>I have seen some instances where a board was "shotgunned" and all of the
expensive hermetically sealed caps (the ones that almost never fail!!!) were
exchanged for cheap electrolytics. I've never believed in doing that,
because I've experienced more failures with the new
electrolytics than with the old mil-spec caps. But in the case of
actually needing to replace one of the expensive caps, if we don't have the
original part, I'll go with an electrolytic unless the customer requests
otherwise.</DIV>
<DIV> </DIV>
<DIV>Don Norwood<BR>Digitrak Communications, Inc.<BR><A
title=http://www.digitrakcom.com/ href="http://www.digitrakcom.com/"
target=_blank>www.digitrakcom.com</A></DIV>
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