[Amps] Long stored SB-220

[Vic Rosenthal 4X6GP/K2VCO]

It certainly wouldn't hurt to remove the tubes and bring it up on a 
variac to reform the capacitors.

The best thing to do with the tubes is to build a device that will let 
you apply a variable plate voltage so you can slowly degas the tubes. 
You want to let the plates glow a dull red for some time to activate the 
gettering process, and if you can do this at a lower voltage, that's 
safer. Then you can increase the voltage to make sure that the tubes are 
OK before putting them in the amplifier.

If you want to be a little less cautious, you could start the amp in CW 
position and either reduce the bias enough to produce enough standing 
plate current to redden the plates or run it into a dummy load with a 
small amount of drive (I suppose it wouldn't hurt to detune the amp to 
increase the plate current) to accomplish the same thing.

You want to be sure that you have a glitch resistor in series with the 
plate supply just in case there is flashover. But you should have this 
anyway.

On 25 Nov 2014 01:42, Tony Brock-Fisher via Amps wrote:
> I recently acquired an SB-220 which has not seen power in 5 years or
> more. What's the consensus on powering up this beast - bring her up
> slow, reforming the caps, worry about gassy tubes; or just plug 'er
> in and let 'er rip? I actually owned this amp in a previous decade,
> so I know I added a lot of protection stuff like diodes on the meters
> etc.
>
> Tony, K1KP

-- 
73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/