Date: Wed, 15 Jun 2016 15:30:11 -0700
From: "David Gow" <d.gow@frontier.com>
To: "'Joe'" <nss@mwt.net>, "'Amps group'" <amps@contesting.com>
Subject: Re: [Amps] Bring a SB-220 Back To Life.
Those tubes ae rated at 4000 volts absolute maximum according to Eimac data
sheets.. Most companies ran them at about 2800. Henry was an exception, my
Henry 3K-A uses a 4000 volt transformer with choke input and the loaded
voltage is about 3600 which is proper for choke input and Henry rated the
amp at 2000 watts OUTPUT. If you are putting 5600 volts on the plates
that is why you are getting so much output but it is way beyond the tube
ratings. Possible someone replace or rewound the plate transformer since
the manual says unloaded plate voltage should be 2500 volts or I hope you
were not running an amplifier jumpered for 120 on a 240 volt circuit which
would make the filaments bright indeed and also eventually make the
capacitors explode, probably. Good luck, I have had several SB-220s and
they are great amps.
Dave W7VM
## IF your tuned choke henry ps is putting out 5600 vdc... instead of the
usual
3600, the reason is obvious. One of the bleeders has opened up.
4000 x .9 = 3600 vdc.
4000 x 1.414 = 5656 vdc
On any of those resonant choke setups, they all suck a ton of bleeder current,
so
the choke looks like a choke. If any of the bleeders opens up, it will now
look like
capacitor input filter. This happens all the time with henry power supplies.
Jim VE7RF
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