[R-390] Capacitors

[Chuck Rippel]

Walter Wilson wrote:

Walter is absolutely right.  I get e-mails nearly daily about replacing 
capacitors wholesale.  There are not that many that need replacing.  
Remember, unlike other Collins designs such as the 75A-4, there are no 
capacitors (except in the audio stages and C553) that couple the grid of one 
stage to the plate of the preceeding stage.  Thus, serving as plate block caps. 
These are under the most stress.

That problem is circumvented by design in that the R390A is largely 
interstage transformer coupled.  They also fail and often.  The problem usually 
first appears as a "popping" on strong signals.

Don't get to "enthusiastic" replacing parts, you may do more harm than good.

>Below are a few items from others that have been posted to this list
> previously.  I hope this helps you make your decision.  Just be careful
>not  to redesign the radio too much. [;-)
-----------------------------
Chuck Rippel, WA4HHG
R390A List Co-Administrator
Reply to: R390A@R390A.com

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1968 Contract Dittmore-Friemuth R390A #38
1967 Contract EAC R390A #2808 with outboard Sherwood SE-3 Sync. Detector
1967 Contract EAC R390A #5295
1967 Contract EAC R390A #5591
1967 Contract EAC R390A #1023

All in regular use as premier Shortwave Broadcast DX Receivers
       -and-
Vintage AM Amateur use
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