[DavGoodlin]

I pulled the chassis last night and saw nothing unusual. the 2-amp line fuse was not open, so I carefully switched it on looking for more smoke, got no smoke/sparks but there was now a moderate hum. All the while monitoring rising cathode voltage on the 6CA4 as heater warmed up.

The first electrolytic after the 6CA4 rectifier tube was the half-circle terminal on the 4-section lytic, which I had disconnected and installed a pricey, new 100 mf @ 250 volts, correct polarity. Im sure this is where the smoke came from, as it smelled like a "new" component fail.
My F***-up for not going with a 350 volt cap, since the 6CA4 cathode measured 280 volts, with a now-open filter. I guess 250 means 250 and NO more. i did not expect B+ over 250 in this set, but the existing 4-section is rated at 350. =( Of course its possible it froze, due to a few sub-zero nights in the shop.
Who knows what this would rise to with a good cap. The schematic inside the cabinet did not show any voltages! Once I see the sams, I may know what the correct voltages are.



Also replaced was about 9 wax-paper caps and a 1 mf/25 v cap at the ratio detector tube, 6BJ7. I did not hold back here except on the x-pensive caps.
I was sure that 100 mf was the source of smoke, since I left the box (40 mf) and triangle (30 mf) as the ESR was OK on those also. I normally replace the first electrolytic filter cap after the rectifier regardless of how it tests, just because 50 years is old enough.
I figure if the down stream filter caps suddenly short, a resistor will get smoked, not a tube and/or transformer.

I looked through the spare parts and had no 450 volt caps close to 100 mf, so I figure on placing 3 x 33mf @ 450 volts in parallel. That should get it.

In the meantime, I can try isolating the silver mica - diseased IF transformer (s), by shunting signal to ground with a .47 cap from grid-to-ground on each of teh 6BA6 IF tubes. This method worked well for me on a Zenith H845 am-fm table radio, kind of like the cylinder-kill switch on an engine analyzer to find an ignition miss.

Then surgery is performed on the IFT removing and repairing it, and likely re-aligning the stage as well.Sure don't want to open up all 5 of them, 2 AM, 3 FM, and a bad mica cap in the base of any one can cause the static on both AM and FM.