[R-390] ReCapping R-390A

[bw]

Dan,

Somebody posted a report by somebody a while back. I have it on another 
computer at the moment. The IERC shields with 'fingers' lining the 
inside of the shield transfer more heat from the tube than any other 
type of shield. The shiny ones seem to reflect heat back to the tube and 
actually raise tube temperatures. Chuck used to have a short list of 
tubes suggested for having shields. Most are best used unshielded.



the other other Barry

>George,  when I got my 390a I sort of did what you did.  I took a look inside
>and assessed what looked bad.  My basic approach is "if it ain't broke,  don't
>fix it."  But I gave in to the idea of replacing the critical cap in front of
>the mech. filters just because that didn't really take much work and there's
>nobody that says it's not going to fail eventually with serious consequences.
>I replaced a few others but more or less when I could tell there was a
>malfunction.  There is one physically small,   cathode bypass cap,  in the audio
>section as I recall,  that invariably seems to be bad and it's condition can be
>spotted and I replaced that.  And I replaced the plug-in power supply caps. So
>far the receiver has operated pretty well.   I would say completely recapping
>the whole receiver is a bigggg  job.   My 390a is one of the later EAC types so
>I expect it might have more life in the original parts than some of the earlier
>versions.  I have no  experience with earlier versions so that statement is
>based on intuition and occasional statements from others to that effect.  The
>general consensus seems to be that the black IERC actually cool the tubes,
>whereas the others are more or less ineffective,  if not worse than no shield as
>far as cooling goes.   Dan
>  
>