[R-390] Orange Drop vs ceramic disc

[Curt Nixon]

rbethman wrote:
> OKAY, just my $0.02 worth.
>
> We are talking about R-390A/URRs that *have* BBODs.  My experience has 
> been that the pre '67 EACs have BROWN BODs.  Such as the '51 contract 
> Collins Blue-Striper I'm restoring.
>
> I've finally located the nasty caps under the RF deck.  I had problems 
> identifying them based on color photos, and discoloration of components 
> from heat.
>
> Looking at this from a "practical" aspect, I don't care to use Orange 
> Drops per se.  They are TOO large and a pain to use.
>
> Now that that is tossed out there, the SP-600 I got in trade in 2004 for 
> my '67 EAC, HAS been recapped underneath with ORANGE DROPS!
>
> I have been running it pretty constantly.  There have been NO issues.  
> My ears are still *real* good.  Why, I have no idea.  I'm NOT an 
> Audiophile, BUT I can hear when there is distortion.  I only here it on 
> a very strong station that you have to start reducing the RF gain, AND 
> the volume.
>
> I've been using some kind of film caps to recap the Collins.  They 
> aren't ODs.
>
> I *think* this is really getting blown out of proportion!
>
> I'd have to ask Barry if having used ODs - "Do you notice ANY degradation?"
>
> Bob - N0DGN
>
> On 4/1/2011 8:54 AM, Cecil Acuff wrote:
>   
>> I think it's important to also mention...there are two different type of
>> Orange Drop caps.  Can't remember the designations without the catalog in
>> front of me but...there are.  I think one is metalized film and the other
>> film/foil types....am I off track here?
>>
>> We need to make sure we don't direct folks using the Orange Drop terminology
>> in a blanket fashion.  As I remember one is recommended and the other not so
>> much.
>>
>> I'll have to pull the catalog to fill in the blanks if someone else doesn't
>> chime in...
>>
>> Cecil
>> ----- Original Message -----
>> From: "Barry"<n4buq at knology.net>
>> To:<R-390 at mailman.qth.net>
>> Sent: Friday, April 01, 2011 7:36 AM
>> Subject: Re: [R-390] Orange Drop vs ceramic disc
>>
>>     
>>>> Those are metallized film capacitors, which for the reasons
>>>> previously discussed (breakdown/self healing) are disasters waiting
>>>> to happen in boatanchors.  I'm not aware of any axial lead
>>>> film-and-foil caps currently available.  Much better to use the best
>>>> part for the job (film-and-foil) and accept a bit of inconvenience
>>>> installing them than to use a lesser part just for convenience.
>>>>         
>>> I wish I had known.  I recapped an R390A with these:
>>>
>>> http://www.justradios.com/capacitors.html
>>>
>>> Barry - N4BUQ
>>>       
>
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>   
Found this interesting discussion of metalized vs foil types and 
specifics of the "healing" mechanism.

I doubt that the energies specified would ever be a catastrophic event 
in any blocking application in a receiver.  Normal levels were said to 
be on the order of 10microwatt-seconds with extremes being 
100microwatt-seconds.  That level surely is not going to be anything 
more than a blip of noise in a tube circuit..even a coupling or blocking 
application at 300V into a grid circuit.

Not saying it isn't a better choice to use real foil types, but I will 
not be red tagging any radios that have self-healing caps.

http://www.electrocube.com/support/metalized_caps.asp

JMHO

Curt
KU8L