Discussion in 'Amateur Radio Amplifiers' started by KK4ZYM, Nov 3, 2015.
are back in stock at RF Parts. They've come down $5 since the last go around.
How could they cut cost like that ?
No more gold plating maybe.
It didn't seem like there would be much incentive to cut the cost when they sold out the last lot in less than a day.
Weeeeeeell I said I wasn't going to but I did. On the bright side I just doubled the value of my SB200
Anyone here ever replaced the 811's in a AL-811 with 572's? I see a lot of people that talk theoretically about it, bash it etc. but have yet to
read from someone that has actually done it and used them for a while.
I know two Locals, WA2WDX has, and so has K2DXN, formerly KD2DXN, and they are happy.
The 572b will take much more abuse than the 811a tubes, and are a drop in replacement, not any higher output power,
but if your antenna swr is not all that good the tubes will live longer. Price of the 811a, vs 572b, that you will have to decide if it is worth it.
Thanks - I was toying with the idea because they should be more forgiving - I had read that you could use 200 Ma grid current rather than
have to be at or under 150 Ma like the 811 and I am sure they would not glow red when I was using them for 100 - 150 W rtty. I have a
tuner at the output, so the SWR the amp sees is always good!
Do a little more searching. This is not something new and hams have been doing this replacement for years. There is a lot of info out there about replacing the 811 with the 572B in the 811 and 811H. I'll never do it in my 811H. Definitely not cost effective and there is no increase in output power.
Check out this link. http://w8ji.com/al811h_schematic.htm
I installed 572b tubes in my 811H. There was a 75-100 watt improvement in output on the 12 and 10 meter bands. However, I would tend to believe that this was due to the previous owners abuse of the 811a tubes.