[R-390] Re: [R-390A] Electrolytic Can Filters C603 & C606

[Drew Papanek]

Bob Camp wrote:

>What is commonly available are plug in cans with octal bases on them. They 
>don't look like the original capacitors but most of them fit just fine in 
>the same location. Some of the cans are plastic and others are metal. I 
>prefer the metal ones, but that's because I dig them out of the trash at 
>work.

Ahhhh!  Man after my own heart.   I'm reading this on a monitor acquired 
from "Curbside Computer" :)

Gutted cases from square octal based relays work well also.  Of benefit is 
that there is no black
uckumpucky to dig out as with the original caps.

One could also dispense with any kind of octal plug.  The new caps could 
simply be installed under
the audio deck chassis.   They could also be installed from above; use 
radial leaded caps and insert
leads through the existing chassis sockets, solder leads to terminals 
underneath.

>Opinion is mixed on just how large a capacitor to use if you do go larger. 
>Bigger capacitors give less ripple, narrower current spikes and higher 
>voltages. Less ripple is good there is some debate about the higher 
>voltages.

The stock value caps are probably on the large value side.  Perusal of the 
Cost Reduction Report
reveals that larger values were used to compensate for the tendency of 
electrolytics to reduce capacitance at very low  temperatures.   Drag out 
the fat caps for when you stick the radio in your igloo.

>Narrow current spikes are not a good idea. The caps that are located after 
>a choke don't have any problems but the input capacitors do.

All is copacetic in spikeland.  The R-390A B+ power supply is choke input.  
No worries there.

>If you decide you need to pick up some more plug in capacitors what you 
>need to be pretty careful about is the can height.

>You don't have to worry much about value or voltage since what ever is 
>inside is
>probably long dead anyway.

The 2 section cap could be a much shorter can.  For uckumpractice, the first 
one I gutted was an octal
can (not from an R-390A) about 2" tall.  I didn't use that can, but it had 
plenty of space to accommodate
a pair of 47uF, 350v radial leaded caps.

[On Fair Radio...]
>Either way they are a likely source if you need to go mail order.

How about that other place further out west?  They'll sell you a reformed 
(iffy proposition at best)
NOS cap for "only" about $40.

If one simply must attempt to use original or NOS electrolytics (with their 
original insides), it would be well to remember that the General Instrument 
units used in the '67 EAC contract are by far the worst.

Drew

_________________________________________________________________
Stop worrying about overloading your inbox - get MSN Hotmail Extra Storage! 
http://join.msn.com/?pgmarket=en-us&page=hotmail/es2&ST=1/go/onm00200362ave/direct/01/