Question

[Sandy W5TVW]

Subject: Question


> I need a 5AR4 vacuum tube and have 4 or 5  5U4 tubes sitting around.  I
> have checked my RCA tube manual and the pin alignment is very similar
> and with nominal re-wiring I think I could use the 5U4 rather search for
> the 5AR4.  Anyone know of any reason why I can't use the 5U4 in place of
> the 5AR4?
>
> Thanks in advance.
>
> Dave, W8QW

The 5AR4 could more suitably be replaced by the 5R4G/GY.  The filament is
very close
to the 5AR4 in current consumption and the other ratings equal or exceed the
5AR4.
The 5U4 could be used if the power transformer is up to supplying another
ampere
of filament current.  Beware of replacing the rectifier with silicon diodes.
Series
limiting resistors will probably be needed as the B+ available with probably
rise
if this is done.  Depends on the condition of the filter capacitors and
voltage
rating, as well as whether the equipment involved would handle the
additional
B+.

73,
Sandy W5TVW

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