[Masonparker]

Replacing a paper condenser  Part# 110377  which is labeled "Condenser - elect.   10 mfd  50 volts".  The question is what type of condenser do I replace this with.

If i use an Electrolytic Capacitor  not sure which side  the (-) or (+) would go.  I know the black band on the old condenser is not a sign of polarity.

 Looking online for 10 MDF  polyester film condensers and I can't find any.

I think my concern is the wording "elect"  does that mean Electrolytic?

[morzh]

If you do not show the sch or at least tell us what radio it is in, it is tough to answer your question. About the polarity.
Wouldn't hurt to mention it.

[Masonparker]

added note from original post.

I did find a 10MDF 400V polypropylene on line

[Masonparker]

Its a Stewart Warner 1812

[morzh]

And the cap's number in the sch is?

[morzh]

110377 is 10uF 25V
112113 - 10uF 50V

##20 and 21.

The cap #20, 10uF 25V, has its PLUS at GND, and its MINUS at the Centertap of the transformer.

[Masonparker]

First let me say thank you.

So i can use Electrolytic Capacitor?

I have to ask by looking at the schematic how did you determine the polarity?

I wish i could find i place that taught a class on radio repair. My 1955 lesson book on How to Become a Radio Repairman is a slow process.

Thanks Again

[RodB]

You can buy 2 electrolytic capacitors that are 10 mfd, one at 35 volts and the other at 63 volts. As Mike said, be sure to install the new ones according to the schematic polarity of each capacitor.

[morzh]

The answers to your questions are:

1. Yes you can use electrolytic cap. I even think it was in the beginning as in those times I doubt a reasonable size 10uF non-electrolytic cap existed. It might but......so, yes, electrolytic is fine and it could be a Generap Purpose one, does not have to be anythings special.
2. The polarity is determined very simply: here's the rule, I am gonna write in in big bold letters:

IN EVERY SCHEMATIC THE NEGATIVE POINT OF THE RECTIFIER (TRANSFORMER CENTERTAP) IS THE MOST NEGATIVE POINT.

This means that the GND is positive relative to it, therefore the positive of a cap will go to it, if it is wired between GND and the centertap of the power transformer output winding.


Oh.....and there is nothing wrong with using film caps either. Then you do not have to think about polarity.

Another point:

The very first cap of the rectifier (right after the rectifier tube) should be a "high ripple" or "low ESR" (I prefer high ripple, though it usually means Low ESR and vice versa) type. The rest could be GP.

[Masonparker]

Thanks for both replying i'm sure i will have another question

[Radioroslyn]

Here's cleaner schematic https://worldradiohistory.com/Archive-Ri...39-STU.pdf  Scroll to pg 195.

#19 33mfd @ 450v + side 5w4 filament. - side hv ct.
#25 10mfd @ 450v + side pin 4 of 6k6 - side chassis
#20 10mfd @  50V + side chassis - side hv ct.

Would use electrolytic caps rather than the polys. They are more common,cost effective, and smaller in size.

[Dan Walker]

The best book I found  for learning radio repair is
 ''The elements of Radio'' by  Marcus and Marcus
 I knew nothing about radio restoration until I read that book.
 It is highly recomended.
Dan in Calgary

[RodB]

Marcus was my first textbook back in '63 high school radio electronics class. Three hours a day, included one hour of lab.

[Masonparker]

Dan Thanks I found the book online and bought it.

Question about Condenser #21  see the attached picture

The schematic to me looks like it should be jumped across the two taps of #4 110786.  It actually goes from the tap on #4 to 6U7G.  If i follow this then what is the (-) and (+)
side

[radiorich]

Hello Masonparker,
First of All Welcome to the Forum !!
Yes I second what Dan said and far as the electrolytic capacitors I like buying from mouser Electronics and I buy my Coupling Capacitors from Sal's Capacitor Corner's And he sells all types of parts and we have some other great guys who sell parts too.

Sincerely Richard