[Boatanchors] Capacitor question

[Chris Bower]

Thanks Chuck, I am going to go with a film replacement. From what I'm
learning it's not going to make a difference.
I'm wi
>
> Chris -
> Long ago, some folks believed you got better bypassing if the outer foil
> of a bypass capacitor was the end that you grounded.   Similarly, they
> might want to use the inner foil to a high impedance grid on an input
> stage.  Current thinking seems to be that the difference isn't big enough
> to be noticable, unless you are one of those audio people with magic ears.
>
> Any good quality .1uf, 1000volt rated film capacitor should work just fine
> in the VTVM.
>
> While you are working on it, may I suggest you also replace the ohms-scale
> battery with a regulated 1.5 volt source run from the 6.3vac filament line.
> An example is shown here:
> http://mikeyancey.com/VTVM_battery_eliminator.php
>
> This is particularly important if you were going to use an alkaline
> battery - as the alkaline PotassiumHydroxide electrolyte is much more
> corrosive than the sulfuric acid electrolyte of the old carbon/zinc cells,
> and there seems to be more of it.  I just finished working on a badly
> corroded RCA VTVM - the electrolyte had ruined the power transformer, two
> tube sockets and a bunch of parts.
>
> Enjoy your project !  May I also suggest you become familiar with the
> Antique Radio Forums:
> http://antiqueradios.com/forums/index.php
>
> 73,
> Chuck K7MCG
> On Sun, Jul 8, 2012 at 4:36 PM, Chris Bower <n8nwham at gmail.com> wrote:
>
>> Hi all, I hope everyone is having a nice Sunday (or whatever day it is at
>> your locale).
>> I have a question about an old capacitor. I'm currently freshening up an
>> Eico 249 VTVM. It was my Dad's, was working when last used about 10 years
>> ago, and still does although it's way out of calibration now. I'm
>> attempting to restore it electrically for daily bench use. Of course, one
>> of the repairs I'm making is to replace most all of the caps. Here's where
>> the question comes in.
>>
>> There is a .1 mfd, 1000 volt capacitor that has no brand name on it, but
>> is
>> marked "Type 85TOC". It is rather large and cylinder shaped, heavily
>> coated
>> in wax, and appears to be made of yellow-colored paper or cardboard. In
>> the
>> schematic, it is connected directly to the test probe in certain function
>> switch positions.
>>
>> Here is my question: one end of this capacitor is marked "Outside Foil". I
>> can't say I've ever seen this before. Could someone enlighten me about
>> this
>> marking? I understand how this capacitor is built, likely two long foil
>> strips seperated by a dielectric strip and all rolled together. But why
>> would one need to know which foil strip was the outside one? It doesn't
>> appear to be an electrolytic capacitor as there are no polarity markings.
>>
>> I can get a very reasonably priced replacement film capacitor from Mouser
>> with exactly the same specs; will that work as a replacement?
>>
>> Thanks much in advanced! I should mention I'm not new to electronics but I
>> am fairly new to Boatanchors. The bug bit me about a year ago...quite hard
>> ;-)
>>
>> Chris Bower
>> N8NW
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>
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