Capacitors and resistance

[Decko]

Do capacitors have resistance? I reference some heater wires to ground using two caps. i realized later that I could have fried the caps if it wasn't for the higher voltage rating. That said it did get rid of the unwanted hum. Then I thought that I should use 100R resistors but they did not work to reduce the hum. Now I am thinking that I coud measure the resistance on the 40 uf caps and use that value to ground the heaters. Any thoughts?

[tubeswell]

Yeah its called ESR

[Jana]

Something else that works, on old cars that smoke a lot, is to drain out all the oil from the engine—it cuts down on the smoking tremendously.


You asked for "Any thoughts?"

Seriously, buy an electronics theory book.

[flood]

i'm just a noob, but my gut feeling says that your plan of action will not end well.

[C Moore]

No they do not have resistance. What they have is capacitive reactance. You need to have some understanding of AC theory for it to make sense to you. Xc is equal to 1 divided by 2 x Pi x frequency x capacitance. Being an AC component it is also frequency dependent.
Unlike DC resistance, which can be added summarily, reactance must be added vectoraly. You need to perform some basic trigonometric functions to arrive at the correct answer. One of these guys with a degree can guide you through it much better than I can. But if you do a search of AC theory.....

[danotron]

In a crude way the caps are changing your heater supply from AC to DC voltage. Use the search here to find a rest of the circuit. You need some dropping resistors.

[flood]

long story short.... use two 100 ohm 2W-5W resistors from each lug to ground (or reference them to the output tube cathode).

however, from the sound of it, it seems you know less about these amps than i do, and i know really very little. please read up a bit more and get some fundamental knowledge on amps.

[Decko]

Hi All,

Thanks for the feedback. Judging by the responses I do apologize for this ridiculous question. Now I am seriously considering a class on AC theory.

[C Moore]

If anything was ridiculous, it was my answer. I really did not grasp the question you were asking until I read your post a second time. You are doing the right thing with the 100 ohm resistors. You may be unbalanced however, and that is why some manufactures (Ampeg) used a 100 ohm potentiometer in place of the resistors. You may find that using a pot will allow you to turn away a lot of the "hum' you are hearing. It would certainly be worth a try.
Good Luck

[Dai H.]

to deal with noise, read about layout, grounding, basic theory. Lots of people don't bother and I suppose if they are working from set instructions that are confirmed, etc. it can work but it's just basically better to know than not.

[Structo]

If anything was ridiculous, it was my answer. I really did not grasp the question you were asking until I read your post a second time. You are doing the right thing with the 100 ohm resistors. You may be unbalanced however, and that is why some manufactures (Ampeg) used a 100 ohm potentiometer in place of the resistors. You may find that using a pot will allow you to turn away a lot of the "hum' you are hearing. It would certainly be worth a try.
Good Luck

Yes as many Fender amps had the hum balance control which isn't such a bad idea.
You can still have adjustable bias and the hum balance.

Does the hum balance pot have to be a wirewound?
Thinking it may only be around a 125ma maybe not?