Selecting THE screen grid resistor value foir my '66 Bassman

[Jerry2013]

So I have been researching the best value resistor to put across the two screen grids of the two 6l6's of the 1966 Blackface Bassman amp.

Guys are saying to stay with the 470K ohm ( edit 470ohm) 1 Watt for purposes of "fusing" , without resorting to an HT fuse. Plus, from what I gather, that 470K 1 Watt stock original resistor value pushes the tube best and sounds best . Some do not like that stock value as it is too easy to fuse /toast.

Otherwise, i have read where some push the value up to 680, for more tube protection .

There is some support for going up from 1 watt to 2 and 3 watt flameproof Metal oxide, which on the screen grids, doesn't seem to matter as far as tone.

I am looking at getting a couple reasonably priced 680K 2 watt Metal Oxide Flameproof resistors.

Right now, I have 1K 5 watt Dale resistors, which are similar in value to cement resistors some people favor.

I am inclined to now believe that 5 watts might be too "loose" bassy -even muddy. Plus they would not fuse in all-to-likely tube meltdown with cheap modern tubes.

Right now, I am inclined to be getting a couple reasonably priced 680K 2 watt Metal Oxide Flameproof resistors.

[rdjones]

Pay attention to your values, the stock Fender value is 470 OHMS, not 470 THOUSAND ohms.

I occasionally use 1,000 Ohms (1K) when changing out these resistors.
In cases where I rewire the socket to allow EL34s 1,500 (1.5K).

I doubt there is any audible tone difference between the types of construction or wattage.

rd

[billyz]

I like the stock fender values of 470 ohms and 1 w. I would much rather replace a resistor when the inevitable tube shorts the screen. I find higher values of resistance do add compression. So consider it a personal taste thing.
El34's are safer with 1k though.

Having said that I have a nice stock of 2w 470 ohm AB resistors and I do use those.

[tictac]

IMHO screen resistors should not be considered as some sort of fuse protection; they're function is to prevent oscillation and keep the power tube from over current damage...

If you'll be playing clean go with the 470 ohm value; if you're going to crank up the volume use 1K/5W.....

TT