I just puchased a Brandes B16 radio. The 280 rectifier tube was missing so I replaced it with an 80. I slowly turned the varactor up and before I got to 75% of maximum voltage, I saw the 80 tube begin to illuminate blue and spark on the inside. I am guessing there is a short somewhere in the rectifier ciruit. Can someone give me any other things to check for with this issue in mind.

Also, can someone tell me if any of the condensors in the condensor block diagram on sheet 2 of the schematic are polarized electrolytics?

Thanks

Greg

Greg, I can't say whether the original caps in the block are electrolytics or not. But the larger ones, at least, you'll probably replace with e-caps. The most positive point in the set is the rectifier cathode, so you can figure out how to arrange the replacement caps' polarity.

Chances are one or more of your filter caps is leaking/shorted causing the 80 to light up.

A 280 and an 80 are the same tube.

Hi Doug,

Can you tell me which pin is the cathode on the 80 tube? You can reference this site

http://www.nj7p.org/Tube4.php?tube=80

Please forgive, I'm learning as I go.

Thanks

Greg

:Greg, I can't say whether the original caps in the block are electrolytics or not. But the larger ones, at least, you'll probably replace with e-caps. The most positive point in the set is the rectifier cathode, so you can figure out how to arrange the replacement caps' polarity.
:
:Chances are one or more of your filter caps is leaking/shorted causing the 80 to light up.
:
:A 280 and an 80 are the same tube.

:Hi Doug,
:
:Can you tell me which pin is the cathode on the 80 tube? You can reference this site
:
:http://www.nj7p.org/Tube4.php?tube=80
:
:Please forgive, I'm learning as I go.
:
:Thanks
:
:Greg
:
::Greg, I can't say whether the original caps in the block are electrolytics or not. But the larger ones, at least, you'll probably replace with e-caps. The most positive point in the set is the rectifier cathode, so you can figure out how to arrange the replacement caps' polarity.
::
::Chances are one or more of your filter caps is leaking/shorted causing the 80 to light up.
::
::A 280 and an 80 are the same tube.

Greg,

The 80 is a filament type full-wave rectifier tube. Pins 1 and 4 are the 5 volt filament connections. Pins 2 and 3 connect to the high voltage winding of the power transformer. The B voltage can be taken off either pin 1 or 4 to the filter capacitor circuit. Looking at the 80 base with the pins facing you, there will be two big pins and directly across two smaller pins. Count the pins with the first large pin to the left as pin #1, next #2, etc.

Radiodoc

Radiodoc

Sorry. This is a filamentary tube. The cathode is the same as the filament, Pins 1 and 4 (the two big ones).

:Hi Doug,
:
:Can you tell me which pin is the cathode on the 80 tube? You can reference this site
:
:http://www.nj7p.org/Tube4.php?tube=80
:
:Please forgive, I'm learning as I go.
:
:Thanks
:
:Greg
:
::Greg, I can't say whether the original caps in the block are electrolytics or not. But the larger ones, at least, you'll probably replace with e-caps. The most positive point in the set is the rectifier cathode, so you can figure out how to arrange the replacement caps' polarity.
::
::Chances are one or more of your filter caps is leaking/shorted causing the 80 to light up.
::
::A 280 and an 80 are the same tube.

Looks like Doug is right. I went to this website and found the answer.
http://en.wikipedia.org/wiki/Vacuum_tube

The filiment is definately the cathode.

Next question. These 6 caps are encapsulated in a black epoxy'd box. I am guessing the #1 & #2 cap are polarized. Can anyone tell me if the remaining 4 caps could be electrolytic as well? If I was to replace these 4 caps with just non electrolytic caps, could this ruin the radio?

Greg

:Sorry. This is a filamentary tube. The cathode is the same as the filament, Pins 1 and 4 (the two big ones).
:
::Hi Doug,
::
::Can you tell me which pin is the cathode on the 80 tube? You can reference this site
::
::http://www.nj7p.org/Tube4.php?tube=80
::
::Please forgive, I'm learning as I go.
::
::Thanks
::
::Greg
::
:::Greg, I can't say whether the original caps in the block are electrolytics or not. But the larger ones, at least, you'll probably replace with e-caps. The most positive point in the set is the rectifier cathode, so you can figure out how to arrange the replacement caps' polarity.
:::
:::Chances are one or more of your filter caps is leaking/shorted causing the 80 to light up.
:::
:::A 280 and an 80 are the same tube.

Greg, I don't think you need to worry about which, if any, of the original caps in question are polarized. You just need to be sure that any polarized e-caps you install as replacements are wired in correctly, polarity-wise.

Except for physical size, e-caps and non-polarized film caps are interchangeable, assuming they are of the same rating and voltage.

:Next question. These 6 caps are encapsulated in a black epoxy'd box. I am guessing the #1 & #2 cap are polarized. Can anyone tell me if the remaining 4 caps could be electrolytic as well? If I was to replace these 4 caps with just non electrolytic caps, could this ruin the radio?
: