You are right. The computer is in a different room than the amp
project, and I got them transposed in the time it took me to walk to
the computer.
The voltages are where they should be.
I see what you're talking about in reference to the HV. I went back
to the schematic for a better understanding.
The reason for my question was I thought maybe the metering circuit
wasn't complete without the tubes in place, but as you say, the
metering circuit pulls right from the board where the multiplier
circuit diodes are. So that meant I had another problem.
The good news is, I found the problem. Once again, according to the
schematic, there wasn't much that could go wrong. I knew the meter
was good because I'd tested it prior to installation. So that left
either the switch or a solder connection somewhere.
The 3 position switch I am using is not original. In putting the
faceplate on the chassis, I damaged the switch. I repaired the damage
and the multimeter now reads the same as my analog Triplett meter.
Thanks for the reply,
Jeff/KD4RBG
---- Original message ----
>Date: Mon, 15 Dec 2008 18:57:46 -0800
>From: Kevin K7ZS <kevin.k7zs@gmail.com>
>Subject: SB-220
>To: Jeff Carter <amps@hidden-valley.com>
>
>Hi Jeff
>
>Sounds like your back on the right track. To answer your question, YES
>the metering should show the HV even without tubes. The HV is present,
>but not conducting until the tube conducts, so there is always HV on
>these amps, and the resistor which feeds the meter is inline all the
>time (when the switch is on the HV position of course)
>
>As for your voltages, they are BACKWARD! The CW position should have
>the lower HV, and the SSB should have the higher voltage. This stems
>from the old days when the legal limit in the USA was 1000 watts DC
>INPUT (CW), and the SSB limit was 2000 watts PEP INPUT (emphasis on
>INPUT). With these amps operating in class AB1, that is about 50-60%
>efficiency, or about 600 watts output. so, all of these amps had the
>lower voltage setting to ensure legal operation based on the law.
>
>Nowadays, most of us tune up in CW, but WITH THE DRIVE LEVEL YOU EXPECT
>TO USE to be a little gentler on the tubes, and then switch to SSB for
>higher plate voltage, and output. As long as you tune with the actual
>drive level you are tuning for, you can switch back and forth between CW
>and SSB for more or less power.
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