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 Post subject: Eico 249 cap
PostPosted: Jun Tue 18, 2019 1:30 pm 
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Location: Clayton, Ind.
I am recapping an Eico 249. Why the big 1000 volt paper cap? Is this to handle a voltage under test? But the top range is 1500....

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 Post subject: Re: Eico 249 cap
PostPosted: Jun Tue 18, 2019 2:46 pm 
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Joined: May Wed 18, 2011 2:40 am
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Location: Littleton, MA
(Note: The schematic can be found in the Boatanchor Manual Archive (BAMA):
http://bama.edebris.com/download/eico/2 ... 32-249.pdf)


The AC function is specified for frequencies between 30 Hz and 3 MHz. At those frequencies, capacitor C1 has a low impedance compared to the 1.375 MΩ resistance of the AC voltage divider formed by the series connection of R2, R3, and R4. Therefore, when exposed to AC with no DC offset, the capacitor has very little voltage across it.

The 1000 Volt rating is to handle situations where the AC has a DC offset, for example when measuring power supply ripple or the audio voltage on the primary of an output transformer. Some VTVMs specify the maximum allowable peak voltage for the AC input, but Eico doesn't specify it in the manual for the 232/249.

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