Hello ,

The power supply in my old radio has 2 Electrolytics capacitors separated by a choke transformer which make the electromagnet of the speaker.
One of the capacitos is 30uF and the other one is 16uF, both rated at 450v .

The 30uf had signs of leaking, and was completely dry.
I opened the can, took of the old stuff, and put a small 220uF /450v inside the old can.

The other one capacitor of 16uF is still good and keep its charge. But for how long i dunno. I wonder if i should replace that one too ? What would you do ?

I suppose they had no 220 uF / 450v in 1936 !!!

16uF is not terrible for filtering and regulation.

Vianney

Replace the other cap too. It is a time bomb.
:Hello ,
:
:The power supply in my old radio has 2 Electrolytics capacitors separated by a choke transformer which make the electromagnet of the speaker.
:One of the capacitos is 30uF and the other one is 16uF, both rated at 450v .
:
:The 30uf had signs of leaking, and was completely dry.
:I opened the can, took of the old stuff, and put a small 220uF /450v inside the old can.
:
:The other one capacitor of 16uF is still good and keep its charge. But for how long i dunno. I wonder if i should replace that one too ? What would you do ?
:
:I suppose they had no 220 uF / 450v in 1936 !!!
:
:16uF is not terrible for filtering and regulation.
:
:Vianney
:
:
:

Replacing a 30uf with a 220uf might work but not needed and may not be wise.

If the 30uf cap was the first cap after the rectifier then a 220uf is way too much... depending on which rectifier tube you are using.

The tube manual tells you the max cap size should be right after the rectifier.

If the 30uf was the 2nd cap or the one after the choke then the 220 may be ok but still way over kill.

You can go up in value a bit but it is best to stay near or close to the original design

Agreed, Replace the second cap with a 20 or 22 mf. Should be plenty considering you have a choke in between. Never increase the size of the first cap by more than 25% lest you fry your rectifier tube.

FYI, chokes were cheaper than electrolytics way back then.

:Replacing a 30uf with a 220uf might work but not needed and may not be wise.
:
:If the 30uf cap was the first cap after the rectifier then a 220uf is way too much... depending on which rectifier tube you are using.
:
:The tube manual tells you the max cap size should be right after the rectifier.
:
:If the 30uf was the 2nd cap or the one after the choke then the 220 may be ok but still way over kill.
:
:You can go up in value a bit but it is best to stay near or close to the original design
:
:

Thanks to you !!

I should have read my tube manual before replacing capacitors...

You were right.
The rating chart for the 5U4G rectifier with capacitor input to filter say: 40uF max, this to avoid increasing the peak plate current.

Ok I will change the second cap also.

Vianney

I would say that if the set is yours and the electrolytic really does test good, and you'd like to make use of it until it doesn't, then keep using it, but add a fuse to the B+. A #47 or 44 (depending on current draw) bulb on the h-v center tap should work.

It is best when using any old electrolytic to first test it on a reforming circuit for a half hour or more to see if there is excessive current draw or heating. If current draw goes down and stays down, then the electrolytic is satisfactory for use. For circuits over 120 VAC it is best to fuse the power supply, though a fuse is good for any circuit.

1930s electrolytics aren't as reliable as the better ones made from the 1940s onward (twist-lock, Mallory, Sprague Atom, and Cornell Dublier). Still, the big wet ones last a long time if kept formed. Their biggest problem is a bad rubber seal, where all of the fluid leaks out. They will get hot and overload the power supply if they need reforming (which, if done properly, can alleviate this problem).

Otherwise, if you're not interested in seeing how long it will last (which could be a long time if the seal holds and you use the device regularly), replace it.

I have made use of many old electrolytics, mostly the better ones I listed, especially when I was younger and money was more of an issue. I have had a few dry up on me over the years, but most still continue to work well for me. Most of these were in fine working condition when obtained, and some were reformed.

T.