just recieved this radio.was checking the tubes.it has the tube lineup of 6p7,6a8,6f6,and a 5u4.the print shows 5y3 or 5z4....is the 5u4 okay to sub for the 5y3

:just recieved this radio.was checking the tubes.it has the tube lineup of 6p7,6a8,6f6,and a 5u4.the print shows 5y3 or 5z4....is the 5u4 okay to sub for the 5y3
:
Yes.

Here's some info to consider on the swap...
A 5Y3 is limited to 125 ma current, 5U4G can supply 225 ma. There is also a difference in internal voltage drop within the tube. A 5U4G will have a lower voltage drop than 5Y3.

One other important item to consider - 5Y3 has a 2 amp filament while 5U4 3 amps. This is ok if a transformer can handle the extra filament current without overheating

:Here's some info to consider on the swap...
:A 5Y3 is limited to 125 ma current, 5U4G can supply 225 ma. There is also a difference in internal voltage drop within the tube. A 5U4G will have a lower voltage drop than 5Y3.
:
: One other important item to consider - 5Y3 has a 2 amp filament while 5U4 3 amps. This is ok if a transformer can handle the extra filament current without overheating
:so it needs a 5y3 to help out on the transf.

::Here's some info to consider on the swap...
::A 5Y3 is limited to 125 ma current, 5U4G can supply 225 ma. There is also a difference in internal voltage drop within the tube. A 5U4G will have a lower voltage drop than 5Y3.
::
:: One other important item to consider - 5Y3 has a 2 amp filament while 5U4 3 amps. This is ok if a transformer can handle the extra filament current without overheating
::so it needs a 5y3 to help out on the transf.
:
:
Yes. I wouldn't make that substitution due mainly to the filament current. That can cause damage to the power transformer.

All the Best,

Bill Grimm