Discussion in 'Amateur Radio Amplifiers' started by N8SAN, Jun 28, 2017.
15=2.0 or better
10=1.5 or better
I've seen sets, 2 sometimes 3 of 8950's out there.
Can you mixed sets of tubes?
So if I come across a good pair, can those go in with the other pair? Or do I need to find a matched set of 4 which would be impossible.
If you go really easy on the amplifier yes you can.
The only time I support matched sets of tubes is in sweep tube amplifiers....
8950s are beefed up sweep tubes....
Really easy meaning, don't run full power for what their worth?
So for instance if a good pair and the old pair can output 800. I should run at 600?
And I KNOW this is a heavily loaded question but is 300 watts reasonable to achieve by swapping out for a good pair?
I think nobody will really know, you just have to try it.
One "problem" with sweep-tube amps is back in the 1950s-60s-70s when million of TVs were being manufactured using them, there were millions of good sweep tubes also being manufactured, right here in America.
That all stopped when TVs stopped using tubes!
Sweep tubes in the 1960s cost $2.95/each brand new and were very good. That's why some rigs and some amps used them.
"Transmitting tubes" were more expensive at the time, so that's why some rigs and amps didn't use them. Now, sweep tubes aren't American made and what anyone is selling is either "NOS" manufactured decades ago, or tubes made in China. IMO, you never really know what you're going to get unless you try them.
They won't put out eight hundred...
On a good day when the line voltage is high you will see a tad over six hundred with a matched set.
If the tubes are too badly mismatched the weak ones will wear down the strong ones since they will be sharing a disproportionate share of the load.
I wouldn't expect more than five hundred watts.
That makes really good sense.
I'm suprised, although maybe I shouldn't be that there isn't Something close to the 8950.
I've seen ones where you change the heater voltage but you lose a lot on the output.
Oh that's makes a lot of sense.
So to me it would make sense to acquire a strong pair. And then another strong pair at a later date. Just keep hunting around.
Then I would have a more evenly balanced set of 4.
Good theory? Or am I off.
Actually there is something close to the 8950, but it is perhaps more rare.
That would be the Sylvaina 6LF6, to use it modification is required. the filaments need to be rewired since the 5LJ6 is a 6.3V filament, the 8950 is a 12.6V filament, otherwise it is a drop in replacement.
You can't use another brand, the Sylvania tube is shorter than an RCA or GE version of the same tube.
Or save up your money and buy two matched pairs that are close from RF parts.
They are expensive by the way.