[R-390] Question to post

[Barry Hauser]

The Scott RCH receivers have four stud-mount oil filled 4 mfd 400v 
capacitors right in a row on the chassis.  They're metal cans but the can is 
isolated from the stud so not (necessarily) grounded.  They have two 
contacts on their bases -- non-polarized.  Not easy to find equivalent 
tubulars so have to be replaced with multiple caps in parallel, I guess. 
These caps last a long long time, but they have insulator material between 
the body and the stud and if struck or "leaned on", can break and leak their 
mojo bug juice.  (Probably PCB-laden oil) I've got one which was broken as 
delivered and one of the other four hanging by a thread.

I've seen Orange Drops listed as high as 2 mfd. but not often.  I believe 
you can put electrolytics in series to make a non-polarized combo - or buy 
non-polarized electrolytics used in speaker crossovers, but wouldn't assume 
they have the right parameters or available in high enough voltage ratings.

Barry

> Jack,
> Not sure but here's my thought. These caps are non polarity and even 
> today, non-polarized caps seem a bit big compared to their brethren 
> electrolytics. Trying to think about 1950 manufacturing gives me pause 
> that Collins couldn't get a 2mf cap either easily or as cheap as two 1mf 
> caps as you suggest. I had one go bad and replaced both of them with about 
> 1.5mf total and it works great.
> 73's
> dave
>
>
>
> At 02:45 PM 5/2/2005, Jack Sullivan wrote:
>>My Collins R390 (not "A" version), on I.F. deck, has
>>two top chassis mounted OIL FILLED condensors, side by
>>side, 1 mf-400 volts each, hooked in parallel, giving
>>2 mf 400 volts.  They are a coupling to AGC circuit.
>>Why in the world did Collins design two such
>>condensors to be wired in parallel, rather than just
>>installing one 2 mf-400 v. condensor, was it, perhaps
>>because a larger 2 mf. wouldn't fit in spot on chassis
>>top, or could it have been that they just didn't have
>>available to them at time 2 mf cond. needed?  Best,  Jack
>>
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