[R-390] R-388 caps (OT)

[2002tii]

Roy wrote:

>Of concern are any silver mica caps you may find.  They are suspect
>now.  Get new replacements from Justradios.com in canada.  Good
>prices, friendly service, and prompt filling of orders.
>http://www.justradios.com/

One caution I would offer -- these folks offer "orange dip" 
capacitors and say they are "dipped in orange epoxy like Sprague 
Orangedrops used to be."  Sprague (now owned by Vishay, which has 
been one of the most highly regarded electronic component 
manufacturers in the world for decades) still makes Orange Drops and 
they are still dipped in orange epoxy.  See 
http://www.vishay.com/docs/42018/715p.pdf, 
http://www.vishay.com/docs/42019/715phv.pdf, and 
http://www.vishay.com/docs/42020/716p.pdf.

Personally, I would use nothing but Vishay/Sprague 715P or 716P metal 
foil and polypropylene caps it tube radios where film capacitors are indicated.

Note well: NOT metallized film -- film-and-foil only.

The source Roy mentioned is about half-price compared to what Mouser 
charges for real 715P Orange Drops (see 
http://www.mouser.com/catalog/634/829.pdf), but until we have 40 
years of experience indicating they are as reliable as the Spragues, 
I'll use the real Orange Drops and happily pay the difference.  The 
real Orange Drops come in substantially larger values, too.

As long as we're on the subject, I never use film capacitors as 
bypass caps -- ceramics are much superior in that role, and no amount 
of desire to "keep things original" would persuade me to use anything 
but the best part for the job when I'm putting in the effort to 
replace 50+ capacitors in devilish locations in a radio.  I do use 
them for all interstage coupling and AGC filtering.

Best regards,

Don