capacitors/resistors

7/22/2009 12:02:30 AMg berg

Hi all ..A quick question.... I noticed that in a few of the 1930s-40s radios that I have restored there are capacitors that are coupled with a resistor..Or in other words a resistor is "piggy backing" on a cap by being connected to both the + and - leads of cap...What exactly is the purpose of this... THANKS...

7/22/2009 12:19:02 AMPeter G. Balaszsy

:Hi all ..A quick question.... I noticed that in a few of the 1930s-40s radios that I have restored there are capacitors that are coupled with a resistor..Or in other words a resistor is "piggy backing" on a cap by being connected to both the + and - leads of cap...What exactly is the purpose of this... THANKS...
:

Since you are indicating that the cap has polarity marked on it... then it is probably an electrolytic so in that case it is ..probably a bleeder resistor to discharge the cap when shut off.

However if the resistor is in the cathode of the output amp tube with an electrolytic in parallel .. then in that case the resistor is used for "cathode bias" so the grid bias can have a negative reference.

The parallel cap in that case is called the cathode "by-pass" cap and is used to stabilize the cathode voltage when the grid signal swings are turning the tube on a good deal drawing more current causing the cathode resistor to have a greater voltage drop.

That causes signal distortion ( negative feed back) and so to counter that...the cap stabilizes and reduces those variations... keeping the grid bias reference point stable.

7/22/2009 12:30:31 AMThank you peter..and others...

::Hi all ..A quick question.... I noticed that in a few of the 1930s-40s radios that I have restored there are capacitors that are coupled with a resistor..Or in other words a resistor is "piggy backing" on a cap by being connected to both the + and - leads of cap...What exactly is the purpose of this... THANKS...
::
:
:Since you are indicating that the cap has polarity marked on it... then it is probably an electrolytic so in that case it is ..probably a bleeder resistor to discharge the cap when shut off.
:
:However if the resistor is in the cathode of the output amp tube with an electrolytic in parallel .. then in that case the resistor is used for "cathode bias" so the grid bias can have a negative reference.
:
: The parallel cap in that case is called the cathode "by-pass" cap and is used to stabilize the cathode voltage when the grid signal swings are turning the tube on a good deal drawing more current causing the cathode resistor to have a greater voltage drop.
:
:That causes signal distortion ( negative feed back) and so to counter that...the cap stabilizes and reduces those variations... keeping the grid bias reference point stable.

7/22/2009 12:31:27 AMg. berg...ooopss..caps are small wax paper caps...

oops caps are the small wax paper caps....

:::Hi all ..A quick question.... I noticed that in a few of the 1930s-40s radios that I have restored there are capacitors that are coupled with a resistor..Or in other words a resistor is "piggy backing" on a cap by being connected to both the + and - leads of cap...What exactly is the purpose of this... THANKS...
:::
::
::Since you are indicating that the cap has polarity marked on it... then it is probably an electrolytic so in that case it is ..probably a bleeder resistor to discharge the cap when shut off.
::
::However if the resistor is in the cathode of the output amp tube with an electrolytic in parallel .. then in that case the resistor is used for "cathode bias" so the grid bias can have a negative reference.
::
:: The parallel cap in that case is called the cathode "by-pass" cap and is used to stabilize the cathode voltage when the grid signal swings are turning the tube on a good deal drawing more current causing the cathode resistor to have a greater voltage drop.
::
::That causes signal distortion ( negative feed back) and so to counter that...the cap stabilizes and reduces those variations... keeping the grid bias reference point stable.

7/22/2009 12:34:02 AMPeter G. Balazsy

:oops caps are the small wax paper caps....
:
:

Still most likely cathode-by-pass on IF stages

Why not post the radio id and schematic instead of generalities?

7/22/2009 12:20:30 AMBill Nielson

well,there's many circuits that employ that configuration.
first of for grid Bias in earlier sets,some later.
2nd for Cathode Bypass i many sets.

7/22/2009 12:26:19 AMBill Nielson

Oops ,didn't notice that "connected to both the + and - leads of cap" part ,Means I must sleep Now ,Goodnight All,ZZZZZZZZZ.
:well,there's many circuits that employ that configuration.
:first of for grid Bias in earlier sets,some later.
:2nd for Cathode Bypass i many sets.
:
:
::Hi all ..A quick question.... I noticed that in a few of the 1930s-40s radios that I have restored there are capacitors that are coupled with a resistor..Or in other words a resistor is "piggy backing" on a cap by being connected to both the + and - leads of cap...What exactly is the purpose of this... THANKS...
::