[Premium-Rx] Tantalums, bead and other varieties.

[Dan Rae]

I think it's important to distinguish between the bead ones that fail 
short circuit, usually on switch on, and can release smoke or even 
explode if there is enough current available, and the regular tubular 
tantalums that Michael O'B was talking about.  I've seen a ribbon cable 
in a 6790 that had one melted conductor.  Guess why!  Not all those 
supplies are current limited.  John Miles and others are correct in 
advising to go to a higher working voltage for the beads.  On the 
6790/GM it seems to be often the 15 µF 25 V ones on the 15 volt rails 
that go bang.  Replace with 35V ones. There were certain batches of the 
beads that were worse than others. I have an RA1792 that had 5 that were 
dead short when I got it.  That was the only time I felt it worth the 
effort of changing all of them in a radio, there are a *lot* of them in 
there, all with swaged leads.  More than a day's work and quite a few $, 
but 5 years later, still no more trouble. 

 I have an RA1772, the family that Michael mentions.  In those, like in 
all 30 year old radios,  the tantalums go leaky and get high ESR as do 
the regular electrolytics, and those are all worth changing out.  The 
difference in the AGC performance before and after in that case was 
amazing, but none were the bead type.

So, if the radio dies, use the nose first!
Dan