I read the article on replacing the ac cord resistor and so I tried it on my Emerson Model 108. It said to use a 10u nonpolarized electrolytic. I didn't have one so sent to PartsExpress and got one. Put it in and the filaments lit too bright as there was 92 volts across the string so sent for an 8u and then I had 75 volts across the string and seemed fine. I ran it for 20 minutes then shut it off. I turned it on a couple of more times for 10 minutes each and the third time it ran for only 5 minutes and smoke poured out and the cap got real hot. Does the cap not have the current carrying capability? I measured and the filaments were drawing .3 Amps. Where can I get a cap that will work?

If you still have the 10MFD. I think it would be alright just to add a resistor. Here is a link to an Ohms Law on line calculator

http://www.the12volt.com/ohm/page2.asp

See how well you do, and come up with the right resistance and wattage.

:I read the article on replacing the ac cord resistor and so I tried it on my Emerson Model 108. It said to use a 10u nonpolarized electrolytic. I didn't have one so sent to PartsExpress and got one. Put it in and the filaments lit too bright as there was 92 volts across the string so sent for an 8u and then I had 75 volts across the string and seemed fine. I ran it for 20 minutes then shut it off. I turned it on a couple of more times for 10 minutes each and the third time it ran for only 5 minutes and smoke poured out and the cap got real hot. Does the cap not have the current carrying capability? I measured and the filaments were drawing .3 Amps. Where can I get a cap that will work?

John the 8uf cap is good but maybe you bought one rated too low in voltage. Lie about 100-150v
That's too little.

Your typical house currunt is probably 125 volts AC (RMS) right?... And RMS voltage is actually 1.41 times greater to the PEAK of the AC.
So with 125v AC RMS you'll need to use a cap that has the capability of actually handling 1.41 x 125v = 177v
So you should try to get one rated for at least about 200vAC or higher.

Now if the cap has a voltage rating on it expressed in DC ....you'll have to reduce it by 40-50% for use in AC.

So for instance ...a 450v DC cap can be de-rated 40% for AC = 270volts

450v - 40% = 270v

::I read the article on replacing the ac cord resistor and so I tried it on my Emerson Model 108. It said to use a 10u nonpolarized electrolytic. I didn't have one so sent to PartsExpress and got one. Put it in and the filaments lit too bright as there was 92 volts across the string so sent for an 8u and then I had 75 volts across the string and seemed fine. I ran it for 20 minutes then shut it off. I turned it on a couple of more times for 10 minutes each and the third time it ran for only 5 minutes and smoke poured out and the cap got real hot. Does the cap not have the current carrying capability? I measured and the filaments were drawing .3 Amps. Where can I get a cap that will work?
:
:John the 8uf cap is good but maybe you bought one rated too low in voltage. Lie about 100-150v
:That's too little.
:
:Your typical house currunt is probably 125 volts AC (RMS) right?... And RMS voltage is actually 1.41 times greater to the PEAK of the AC.
:So with 125v AC RMS you'll need to use a cap that has the capability of actually handling 1.41 x 125v = 177v
:So you should try to get one rated for at least about 200vAC or higher.
:
:Now if the cap has a voltage rating on it expressed in DC ....you'll have to reduce it by 40-50% for use in AC.
:
:So for instance ...a 450v DC cap can be de-rated 40% for AC = 270volts
:
:450v - 40% = 270v

Thanks,Peter. Sounds good. My cap only has 100 volt rating....BUT WHERE CAN I GET an 8u rated 200v or higher??

:Thanks,Peter. Sounds good. My cap only has 100 volt rating....BUT WHERE CAN I GET an 8u rated 200v or higher??

Here:
http://www.goldmine-elec-products.com/prodinfo.asp?number=G12729

::Thanks,Peter. Sounds good. My cap only has 100 volt rating....BUT WHERE CAN I GET an 8u rated 200v or higher??
:
:Here:
:http://www.goldmine-elec-products.com/prodinfo.asp?number=G12729

Well, I looked at that one but it is only a 4 and I will need a 7.5 or 8ufd

Here is a link to " Just Radios " has what you need.

http://www.justradios.com/orderform.html

:Here is a link to " Just Radios " has what you need.
:
:http://www.justradios.com/orderform.html

Looked on that link and they don't appear to have that cap. either.

I am looking at that page now.

Under 450 Electrolytic they have an 8MFD at 450 for $1.15

: I am looking at that page now.
:
:Under 450 Electrolytic they have an 8MFD at 450 for $1.15

I don't think a polarized one will work...Will it?

This is a DC rated cap at 450. As peter said in his post, this will now have a rating of 270 used in an AC application. That should be just fine.

:This is a DC rated cap at 450. As peter said in his post, this will now have a rating of 270 used in an AC application. That should be just fine.
-------------------------------------

That is not correct.
DO NOT use polarized electrolytics.

A DC rated cap MUST ALSO be NON-polarized for use in AC applications.

So you must simply get non-polar caps that have a DC rating of 400v or more ...or are rated for AC @ 200v or more

The link I gave you for :
http://www.goldmine-elec-products.com/prodinfo.asp?number=G12729
has other value caps. If you cannot find an 8uf there you can put two 4uf caps in parallel.

Thought the subject was covered as to back to back making an npo ?

:Thought the subject was covered as to back to back making an npo ?

Hi Warren:
Back to back electrolytics? Yes, that certainly can be done.

I have done it. And as an experiment it certainly worked.

However I did feel a little too much heat being generated. So there must somehow have been leakage going on somehow.

So although it ought to work... and maybe it can work... it may be just more prudent to use non-polars to get the job done safely.

Yeah Peter, if it was me playing with this, I would start off with the 10MFD npo 450 and around a 60 ohm 5 Watt wire wound in series .. Seems that should do it ..

:Yeah Peter, if it was me playing with this, I would start off with the 10MFD npo 450 and around a 60 ohm 5 Watt wire wound in series .. Seems that should do it ..

Hi Warren:
Yes Warren that would work ..But why generate all that heat with such a big resistor? Why not let the cap do all the work?
With a 60 ohm resistor it would drop 22 volts causing a lot of heat requiring a 5 or 10 watt resistor.

You can easily allow the dropper cap do some of that voltage dropping at NO heat at all because of the voltage/current phase shift.

Since part of the idea of a dropper cap is to avoid all that wasted heat ...I find ( using the formula) that an 8uf cap with a 10 ohm surge resistor is better. The surge resistor will only drop a few volts and can be as little as 1 or 2 watts.