WARNING on 811A's

[Jack, W7EJJ]

TUBES FOR LINEAR AMPLIFIERS USING 811A.

Stay away from Cetron 811A's. Out of three the plate caps have come off of
two. They are not bonded very good. Spend a little more money and buy
Svetlana 572B's, they are built like Russian Tanks. The Svetlana 572B is a
direct replacement for the 811A in all cases except the Yaesu FL-2100 series
of linear amps.
-
Jack, W7EJJ

[Mark Keith]

"Jack, W7EJJ" <mal...@c2i2.com> wrote in message news:<trrra13...@corp.supernews.com>...

Dunno, I have to kind of disagree with that assumming normal tube
values. The 572 really needs a higher plate voltage than the 811a's.
I've heard of many people having problems with parasitics, and excess
oscillation problems using 572b's with the lower voltages that most
811 amps use. If I had an 811 amp, I'd stay with 811's unless you can
cough up 2400 volts. Thats what the 572's like to have . Most 811 amps
run 1800 volts or less. Just my 3 cents...BTW, I thought cetron went
out of biz long ago...Did they crank up again??? I still have a set of
old cetron 572's in a sb-200. They made good 572's back in those days.
Dunno about the 811's... Didn't know they made them. I had thought
most people were using the Svetlana 811's in 811 amps?? Did they quit
making 811's? MK

[Jack, W7EJJ]

Cetron's are not made any more, but some suppliers have a big stock of
them left over (or bought them surplus).
Svetlana says use the 572B in place of the 811A. I can only assume from
this that they will not make any more 811A's. BTW you cannot find anybody
with Svetlana 811A's in stock.
RF Parts Co. also recommends Svetlana 572B's as a replacement for
811A's. Go to their website and they have much info on using 572B's in place
of 811A's. www.rfparts.com
Only 811A amps that will not take 572B's direct is the Yaesu FL-2100
series, but Svetlana has a Technical Bulletin on how to modify the Yaesu
FL-2100 series so you can use the 572B's. The Yaesu FL-2100 series of amp
will go into oscillation that is the reason for the Tech. Bulletin on how to
modify.
The 572B's operate great at 1.5 KV and just loaf along at 600 watts for
the AL-811 which has 3 tubes, they also work great in the AL-811H which has
4 tubes.
-
Jack, W7EJJ

"Mark Keith" <nm...@wt.net> wrote in message
news:25eb70d7.01100...@posting.google.com...