(ET) Fw: E15 control board #1

I wonder what is going on with using that size(capacitance) capacitor. Since the time constant of an RC network is R times C, that network would have a time delay 50 times as large as the original diagram indicates. Using a resistor 50 times as large also would result in a time delay 2500 times as large. To get the same delay with a capacitor 50 times as large requires a resistor with only one-fifti-eth of the resistance. The wattage rating of the resistor might need to be changed also. The circuit current would be different also.

Rhett T. George wrote:
The board I am working on has in locations C104, C104, and C105 50
uF, 50 V caps.
The schematic shows 1 uF, 100 V caps at those locations.
My question is, "Has anyone come across this discrepancy and
resolved it to his/her
satisfaction?"

As my card failed, I just connected pins (10) to (11), etc. Let me
take a cut at this circuit: The cap cause a delay between switch 1A
closing (10) and energizing the coil of relay 1A (11) determined
mostly by C103 and R 109. They delay uni-junction transistor Q101
from triggering SCR 106 on. The SCR then connects (10) to (11).
Larger cap or resistor increases the delay. The circuit may also
protect the switches from in-rush current while the contacts are
just making. Not as big a deal as avoiding arcing when the switch
opens. CR106 and R105 may help this.

"Also the 100V caps probably have twice their 'rated' capacity at
half the voltage." Not true. Capacity is related to area of the
foils connected to the wires, and the thickness and type of
dielectric between them. Doesn't vary with applied voltage (much).
What is true is that capacitors built for half the voltage could
have nearly twice the capacity in the same size package, as the
dielectric can be thinner without shorting. Both would store about
the same energy at rated voltage if I remember right.

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