My Christmas day 9T246 restoration! Almost.....

[M3-SRT8]

Now you see 'em...



Now you don't...

[Penthode]

To further belabor the reforming of an old electrolytic capacitor discussion , the reforming takes time, especially if the capacitor has remained dorment.

Last year, when I restored an RCA 9TC275 (1949 with a 16AP4)) according to the original owners, the set had sat in a basement since 1964 un used. This set was a good test case as someone plugged in the set and melted one of the 5U4's literally!!

I was curious if the capacitors could be revitalized after this abuse. I found all the electrolytics almost a dead short. I left in position each electrolytic can on the chassis and isolated the connections to individually test each capacitor. I used my Sprague TO-6 to reform the dielectrics one-by-one. Each electrolytic section took about two to three hours to reform. After replacing all the paper capacitors and a few other components (mostly bad tubes and resistors) I ran the set on the bench for a couple of weeks, keeping an eye on the electrolytics. A 40ufd section of a multi-section capacitor opened and i replaced it with a new old stock multisection unit (after reforming it). I now use the set almost daily and it is reliable without any capacitor issues.

What must be remembered is that even the dry electrolytics have a healing property. The crumbliness when disassembly is normal and does not necessarily mean the capacitor is bad.

Incidently, I am still working on my CTC5 and it was another long time dorment set with shorted electrolytics which reformed nicely apart from two Canadian Mallorys which was part of the Canadian 25Hz modification. The US RCA original capacitors all restored fine and are healthy with leakage below 100uA at full rated voltage.

I would encourage all to consider at least testing the components before condemning them.

Saying that, I have also done my share of restuffing over the years. My method is to slice the can about half an inch higher than depicted above. That is, about 1/2" above where the can becomes larger in diameter. I then obtain short section of aluminum tube slightly larger in diameter than the electrolytic and cut a 1" length. I then carefully slice it to remove a longitudinal section to reduce its diameter just enough to ensure a force fit on the inner diameter of the old electrolytic tube. I install new internal capacitors and then press fit with a vice the capacitor back together over the prepared 1"section of tube. The result is clean and barely perceptible from the original.

[cbenham]

Originally Posted by M3-SRT8

Now you see 'em...

Now you don't...

Does anyone know if the black cardboard tubes you have used are available anywhere new or even new old stock?

I used to see them in the mfgr.'s catalog and in the radio supply stores but
no more. Seems like these would be a good sale item for restorers.

Cliff