[maxhifi]

Consider that the voltage could be low for another reason, before modifying the design by adding diodes. Most likely either something is drawing too much current, or the voltage shown on the schematic represents an average value, which is subject to a tolerance.

How much too low is the B+ voltage? Can you show the portion of the schematic which is effected? I would say that you should check all resistors for tolerance and the tube bias voltages before changing anything. In the worst case you could put even more current through something which is already drawing too much current and cause damage, with the diode mod.

If a circuit isn't working properly, it's better to find out why, instead of employing brute force type solutions to force the numbers to look good.

Another thing to be wary of when changing out rectifier tubes for diodes, is that the tube has a warm up time, and the diode does not.. thus the B+ may surge to a value exceeding that of the filter capacitors voltage rating before the other tubes in the TV warm up.