Jim, I would suggest a bit more than a minute or two.. You may want to
pop that question over on rec.radio.amateur.amps and get the group
opinion... I would suggest a 24 hour filament preheat after long
storage... There is no more effort in letting it cook 24 hours than
for 3 minutes...
I have no direct experience with the 8877 but I do speak 4cx800... The
majority of the amp builders getter new tubes with filament heat only
for up to 24 hours before applying HV.... One of the failings of hams
is that we seem to think that turning on the filament is wearing out
the tube... Whereas the broadcast industry turns the filaments on and
leaves them on because they know what wears out the tubes is cycling
the filament from cold to hot over and over...

I just finished bringing a 3CX1200D7 back to full output with a
controlled filament over voltage for 6.5 minutes with no HV applied...

cheers ... denny / k8do


Jim Barber wrote:
I have several Eimac 8877's I bought as tested new-equipment pulls
around 5 years ago. I tested them again myself at the time, then packed
them away.

Here it is 5 years or so later. The question for the panel is how long
should I "cook" the filaments before putting plate voltage on?

Thanks,

Jim, N7CXI