> Corona in a amplifier with a 3000V anode supply?
>
> >I thankyou Alek for that information. I don't think I'll pursue it
> >anymore. The amp I have is 15 plus years old with the original
> >3-500Z tubes and it still puts out 800 watts PLUS, with no sign of
> >arcing, at least not yet. I have never heard of corona washers
> >before belive it or not. I still learn something everyday, and that
> >is good.
Anyone who has built a Heath SB-1000 is very familiar with the corona
washer. It is included with the kit. Perhaps one can download the manual
from BAMA or somewhere if you want to see pictorials and installation
instructions for it. It is a simple flat washer that is placed on one of the
band
switch contacts.
There is seldom any one cause for the need for special additions to an
amp design. W8JI explains well on his web site the proper way to construct
a band switched tank assembly. Heath had no control over the level of
soldering expertise that Joe Six-Pack would have, so they hedged their
bet with the washer. In addition, the nearness of that particular switch
terminal
to the chassis and other components (layout) is something unique to the
SB-1000. Because this amp operates on at least 8 bands including 160 meters
in a very small RF compartment using all air wound inductors, all bets are off
concerning how much corona and point-to-point arcing can occur. Depending
on the load and tuning (or mis-tuning) it is certainly enough to toast the band
switch on the SB-1000. It was certainly enough to toast a Radio Switch Corp.
model 86 switch on my 8877 amp with a similar layout to the SB-1000.
This tells me that a >7000 volt arc can be produced from a 4000 volt anode
supply. The model 86 switch does not have multiple fingers that
short out unused taps on the tank coil. This style switch prohibits successful
use on more than the traditional 5 bands (80-40-20-15-10m) without resulting
fireworks. (been there, done that, $136 mistake!) If you will look at the band
switches on the AL-1500, Alpha 77 series, and other 6-9 band amps, you will
see how each manufacturer avoided making a nice Tesla coil out of a tank
circuit.
Sorry for the rambling, but I wanted to cover a couple of topics.
(((73)))
Phil, K5PC
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