Silver Mica w/ EM on it

[angelodp]

Hi, I have a stash of silver mica caps - 250pf has a 10% EM on it.

Looks good any way of knowing the rating for these voltage wise?

[ApexJr.]

The EM is only the manufacturer - Elmenco
There are 4 types of silver mica's
Commercial - DM 05, DM 10, DM 15, and DM 19
Military would be the same except CM and if military it would
be on the part CM15 251K
You'll need to look up these numbers on the internet and go by
the sizes to get your rated voltages.

[angelodp]

Thanks Steve, all I see on here is EM 250 +- 10% no other codes??

Ange

[gui_tarzan]

A capacitor reference chart says that 250 = 25pf.

[angelodp]

My cap meter shows 250pf

[angelodp]

EM appears to stand foe El Menco and they are Vintage, or so some articles say.

[tubeswell]

Get a 1000V variac, wire the cap in series with a 10W 150R resistor (for fail-safety to protect your variac), and clamp a 15V decent rated power zener in parallel with the resistor. Hook the variac up across the cap and resistor in series. Now start winding the voltage up, whilst measuring the voltage drop across the cap. If you get to 450V and it still doesn't short, I'd say it'd be good for 500V. If it does short, it was never gonna be any good for a tube amp anyway.

[ToneMerc]

EM appears to stand foe El Menco and they are Vintage, or so some articles say.

EM stands for the Electro Motive company and their brand was El Menco. They made great caps, the film caps were licensed using the original Sprague 6PS dielectric forumla and the dipped silver micas are great caps too. I usually will use the older EM and CD dipped silver micas over any of the modern stuff.

Do you have any pictues or measurements? I can give you an estimate ofthe voltage ratings.

TM

[ApexJr.]

Here are the 4 different sizes, I should have done this first
since I have stock.

[angelodp]

Hi, Here is a shot of one of caps. Any idea on voltage rating for this?

thanks


[IMG768]http://i260.photobucket.com/albums/ii9/angelodp1/IMG_0372_zpsf570cf80.jpg[/img]

[ApexJr.]

This looks like a DM15- CM05 so rated at 500V

[angelodp]

thanks for that.

[angelodp]

Would this be 500v as well?


[IMG:768:1024]http://i260.photobucket.com/albums/ii9/angelodp1/IMG_0373_zps21dc194b.jpg[/img]

[ApexJr.]

Yes, those too look like the DM 15 type rated at the 500V