[R-390] Orange Drop Capacitors

[Flowertime01 at wmconnect.com]

WB5KXO,

The Collins engineers were limited by two things...cost and available 
technology at the time.  There were no doubt better caps available than was 
used in the R-390A...all one has to do is look back to the R-390/URR to see 
that, but cost was the culprit.  Cecil Acuff, Very true. Collins was limited 
to parts already qualified as military acceptable. Getting another part into 
the support system cost money.

Most of the caps I am aware of that are 
being replaced in the "A" are paper caps and the orange drops are very well 
suited to the job and should out last the original paper caps by a factor of 
at least 2. 

Consider that the factor was at least 30 years. 

 No question other caps available today will also do the job. 
I've seen anything from yellow poly caps to German made film caps.  All will 
work.  I guess if you wanted to you could change them all with ceramic disks 
as is done in the SP-600 series.  I think the orange drops have better 
characteristics for coupling and use in audio stages than the ceramics which 
are well suited for bypass work.  In summary the orange drop is just hard to 
beat for all around general use....and by all means stay away from anything 
NOS in paper capacitors.

Cecil Acuff K5DL

-----------------
Good stuff from Cecil.

The orange drops are just considered quality parts. You expect every one to 
work as rated and last.

There are much smaller parts than the orange drops. I used some other small 
brand in my IF deck. I have so much more space in the deck than before. and 
more than if I had used the orange drops.

Most times the orange drops are rated 600 volts. And 300 volt or even 250 
volt caps will do fine. The lower voltage is smaller parts size. The higher 
voltage is less likely to fail ever under use at the R390 voltages.

Collins was not trying to use bad stuff. You can only buy what is in stock at 
the hardware store. Collins could only use what had a stock number and was a 
part that could get issued. 

Every part that was not a stock item cost money to get into the logistics 
supply chain. After the front panel, wire harness, filters, RF transformers, how 
many other new parts do you want to introduce at the cost if there is 
something in stock already that will work?

Roger. AI4NI