this is the Audioromy FU29 pp amp, the main issue with this amp
is "red plating" since cathode is common to both sections,
the only way to balance currents in both plates is thru fixed bias....
(actually there are two other mods that can be done, one is by manipulating
the filament voltage, and the other by tweaking the screen grid voltage
from its set point of about 200 volts....i am looking to implement these
in my upcoming 829b builds)
in order to fix the issue, i changed bias to cathode resistor bias instead...
a 270 ohm 5 watt resistor drops 17 volts, so that at idle, total
plate dissipation for both tubes is about 26 watts, so that either
plate is dissipating about 13 watts...remember that this tube can dissipate 60 watts...
so that longer life expectancy for the 829b is more or less secured....
before mods..
after mods..
other mods included changing plate caps to ceramic type...
the nylon type used was actually a solderless connector...
