Hi Scott
The values you mention will work fine. These filters have a wide tolerance. If you can not find one with the same value, it's best to use the next higher value. Do not use an extremely high value, 100 mfd, as this may overload the rectifier and caused reduced life of the tube. A capacator acts as a heavy load (short circuit) until charged and the larger the value the more time it takes to charge. Like you mention, always use a voltage rating equal to or greater than the original.
Norm
: Hi Scott
: The values you mention will work fine. These filters have a wide tolerance. If you can not find one with the same value, it's best to use the next higher value. Do not use an extremely high value, 100 mfd, as this may overload the rectifier and caused reduced life of the tube. A capacator acts as a heavy load (short circuit) until charged and the larger the value the more time it takes to charge. Like you mention, always use a voltage rating equal to or greater than the original.
: Norm
: Hi Scott
: The values you mention will work fine. These filters have a wide tolerance. If you can not find one with the same value, it's best to use the next higher value. Do not use an extremely high value, 100 mfd, as this may overload the rectifier and caused reduced life of the tube. A capacator acts as a heavy load (short circuit) until charged and the larger the value the more time it takes to charge. Like you mention, always use a voltage rating equal to or greater than the original.
: Norm
Hi Scott, I disagree with Norm, You can use a much higher
value, such as a 100 uf @ 150 or 200 volt if nothing else
is available provided you consider one thing that Norm
did mention, CURRENT. By raising the value of the
resistor between the rectifier cathode and the input
to the first filter capacitor you limit the current in
the circuit. Many of these circuits never had a resistor
in the circuit to begin with so a good starting value
is 200ohm 4watt wirewound. Measure the current between the
cathode and the new resistor and if it is too low, lower
the resistor value to maybe 100ohms. Max. average current
for a 35W4, or 35Z5 is 100mA, so with your meter in the
circuit turn the set on. As the heater warms up the current
will start to rise. If it appoaches 100mA shut the set
off quickly and go to a higher value resistor then perform
the current test again until the best value is found.
Incidently, I've found some two capcitor sets (50uf, 30uf
@ 150v) will perform with the 100uf cap alone but this
is not recommended since you could develope problems
with audio motor-boating. Goodluck
Bob
: : Hi Scott
: : The values you mention will work fine. These filters have a wide tolerance. If you can not find one with the same value, it's best to use the next higher value. Do not use an extremely high value, 100 mfd, as this may overload the rectifier and caused reduced life of the tube. A capacator acts as a heavy load (short circuit) until charged and the larger the value the more time it takes to charge. Like you mention, always use a voltage rating equal to or greater than the original.
: : Norm
: Hi Scott, I disagree with Norm, You can use a much higher
: value, such as a 100 uf @ 150 or 200 volt if nothing else
: is available provided you consider one thing that Norm
: did mention, CURRENT. By raising the value of the
: resistor between the rectifier cathode and the input
: to the first filter capacitor you limit the current in
: the circuit. Many of these circuits never had a resistor
: in the circuit to begin with so a good starting value
: is 200ohm 4watt wirewound. Measure the current between the
: cathode and the new resistor and if it is too low, lower
: the resistor value to maybe 100ohms. Max. average current
: for a 35W4, or 35Z5 is 100mA, so with your meter in the
: circuit turn the set on. As the heater warms up the current
: will start to rise. If it appoaches 100mA shut the set
: off quickly and go to a higher value resistor then perform
: the current test again until the best value is found.
: Incidently, I've found some two capcitor sets (50uf, 30uf
: @ 150v) will perform with the 100uf cap alone but this
: is not recommended since you could develope problems
: with audio motor-boating. Goodluck
: Bob
: : : filter caps must be. I know the max voltage must be
: : : equal or greater, but how critical is the capacitance?
: : : A set I'm working on has three 40 mfd and one 30 mfd
: : : filter caps which are all excessively leaky. The
: : : closest I can come in new stock replacements are 47
: : : and 33 mfd. I assume these should work fine since
: : : this cap application is not real critical, but what
: : : are the general guidelines in tolerance for
: : : electrolytics? Thanks. Scott Rhode
: : Hi Scott
: : The values you mention will work fine. These filters have a wide tolerance. If you can not find one with the same value, it's best to use the next higher value. Do not use an extremely high value, 100 mfd, as this may overload the rectifier and caused reduced life of the tube. A capacator acts as a heavy load (short circuit) until charged and the larger the value the more time it takes to charge. Like you mention, always use a voltage rating equal to or greater than the original.
: : Norm
: Hi Scott, I disagree with Norm, You can use a much higher
: value, such as a 100 uf @ 150 or 200 volt if nothing else
: is available provided you consider one thing that Norm
: did mention, CURRENT. By raising the value of the
: resistor between the rectifier cathode and the input
: to the first filter capacitor you limit the current in
: the circuit. Many of these circuits never had a resistor
: in the circuit to begin with so a good starting value
: is 200ohm 4watt wirewound. Measure the current between the
: cathode and the new resistor and if it is too low, lower
: the resistor value to maybe 100ohms. Max. average current
: for a 35W4, or 35Z5 is 100mA, so with your meter in the
: circuit turn the set on. As the heater warms up the current
: will start to rise. If it appoaches 100mA shut the set
: off quickly and go to a higher value resistor then perform
: the current test again until the best value is found.
: Incidently, I've found some two capcitor sets (50uf, 30uf
: @ 150v) will perform with the 100uf cap alone but this
: is not recommended since you could develope problems
: with audio motor-boating. Goodluck
: Bob
Hi Scott, I disagree with Bob!
We really shouldn't go around measuring current and stuff like that because we will probably kill ourselves with one of these ac/dc sets....!! and if we start raising the value of the caps too much who knows what is going to happen next...lordy lordy...