I have a Stewart Warner series 900 radio. It came to me without tubes so I was going to rely on the schematic. Ryders volume 1- 7. The problem is in the schematic it shows a 280 BUT in the tube position chart marked "Model 900 Series AC", which is how my radio is marked, it shows an 83. The chassis is not
marked for tubes as in some older models.

Both of these rectifiers are equivalent, with 4C basing. But, you don't need to use a tube marked 280 or 283 -- just use an 80 or an 83, whichever you like the looks of and fits your budget.

Though both will work, the 83 is actually the equivilant to a 5U4, whereas the 80 is equivilant to a 5Y3 or 5Y4. The 5U4 does work in most 5Y3 circuits, but if the transformer cannot handle the heavier filament current, it may overheat. When you make a sub, keep this in mind and compare original transformer temperature with new temperature. Also, though about 90% of people will not run into this problem, if you obtain some strange piece of equipment like the Heath O-2 oscilloscope (one of their first oscilloscopes from the 1940s) that uses a 5Y3 in the high voltage rectification section (1000 volts), if you sub a 5U4 in this application, it will blow up. It can handle high current, but the high voltage will jump through the tube.

Thomas

:Though both will work, the 83 is actually the equivilant to a 5U4, whereas the 80 is equivilant to a 5Y3 or 5Y4. The 5U4 does work in most 5Y3 circuits, but if the transformer cannot handle the heavier filament current, it may overheat. When you make a sub, keep this in mind and compare original transformer temperature with new temperature. Also, though about 90% of people will not run into this problem, if you obtain some strange piece of equipment like the Heath O-2 oscilloscope (one of their first oscilloscopes from the 1940s) that uses a 5Y3 in the high voltage rectification section (1000 volts), if you sub a 5U4 in this application, it will blow up. It can handle high current, but the high voltage will jump through the tube.
:
:Thomas

The 83 is not a replacement for the 5U4. The 83 is a mercury vapor rectifier with different rstings. You must be thinking of the 83V which has simular but lower ratings. The 83V also has the four pin base like the 80

Hi

For a radio you would be better off using an 80 (2 amp filament) rectifier. If more current is needed a 5Z3 (3 amp filament).

A 83 mercury vapor rectifier can cause noise in a radio if the circuit isn't designed for this tube. B+ voltage will also be higher with an 83 as mercury vapor tubes have a voltage drop of 15 volts. An 80 will be closer to 50-60 volt drop.

Although an 83V will operate in the same socket it's a close spaced rectifier. This tube will have a lower voltage drop (20-25 volts) than 80 and can arc over in some circuits.

Norm

::Though both will work, the 83 is actually the equivilant to a 5U4, whereas the 80 is equivilant to a 5Y3 or 5Y4. The 5U4 does work in most 5Y3 circuits, but if the transformer cannot handle the heavier filament current, it may overheat. When you make a sub, keep this in mind and compare original transformer temperature with new temperature. Also, though about 90% of people will not run into this problem, if you obtain some strange piece of equipment like the Heath O-2 oscilloscope (one of their first oscilloscopes from the 1940s) that uses a 5Y3 in the high voltage rectification section (1000 volts), if you sub a 5U4 in this application, it will blow up. It can handle high current, but the high voltage will jump through the tube.
::
::Thomas
:
:The 83 is not a replacement for the 5U4. The 83 is a mercury vapor rectifier with different rstings. You must be thinking of the 83V which has simular but lower ratings. The 83V also has the four pin base like the 80

Yep. I mixed them up.