to replace or not to replace

[radio nut]

My current project is a capehart by farnsworth radio model 21n 2. This set has a chassis for the tuner and a seperate one for the amp/power supply. This set reminds me of military set with its oil filled caps and resistors and caps on terminal strips. I tried to variac the set up with original parts but the electrolytics didn't like me too much. I ordered all new caps and I should be getting them soon. A friend said that the oil filled caps will not go bad and unless they leak do not replace them. Ok, is this good advice or a recipe for problems? I have worked on military with oil filled caps but my job was just to get the set functioning, not restore them. I have no idea about the lifespan of oil filled caps.

[bob91343]

I have some oil filled capacitors that test fine. They are stamped with a 1946 manufacture date.

[Electronic M]

I've been wondering if empty oil filled caps can be fixed by refilling?

[compu_85]

I'd be worried about the PCB's in the old oil.

-J

[marty59]

Originally Posted by compu_85

I'd be worried about the PCB's in the old oil.

-J

Did all (old) oil filled caps use PCB's? I've seen A/C motor-run caps that were but I've always wondered about the others....

[holmesuser01]

As long as they aren't leaking, you are OK.

[bob91343]

Amazing how nobody worried about PCBs back then, and I never heard of a case where a problem occurred.

Yes you can refill the oil but there are some practical problems associated with that. Sealing is the toughest and, of course, what oil to use. Those old capacitors were sealed by crimping, and the terminals were sealed with a grommet of some sort. The interaction of materials is the prime concern; will the grommet contaminate the oil, or the oil dissolve the grommet, and what about temperature considerations. It's safer and cheaper to get a new part.

[radio nut]

well, I put in all new paper and electrolytic caps and will replace the oil filled ones this weekend. I have been running the set and I have an unusual problem. After a while it seems to lose signal and starts humming. If I change bands the humming goes away for a while. Is this a cap oriented issue? I did try a contact cleaner but its not exactly de-oxit.

[radio nut]

Well it seems like I answered my own question, I replaced the oil filled caps and now I have no problems. So I will calibrate the set and enjoy listening to it!

[ctc17]

I found a big bag of them and tested them just for fun. 80% were bad. Good choice to replace.