On Thu, 03 Dec 2009 16:45:27 -0600, Dr. Gerald N. Johnson wrote:
>The metering circuit is likely made with 5% parts and power line
>voltages are allowed 10% variation in most states.
Yes. I don't know about the Centurion, but the Titan 425 also
includes a pot to calibrate the HV.
Another point. Reduced HV B+ is also a symptom of a bad filter cap
in the power supply. If you start getting reports of hum or a funny
CW note, that's the problem. These amps use 8-12 450V caps in a
series string with a 2W resistor across each to equalize the
voltage. Typically one at a time of these caps will go bad, adding
ripple and dropping the B+.
They are easy to troubleshoot with an old fashioned mechanical VOM
(like a Simpson 260) on the high Ohms range. With power off and
everything discharged for a long time (the minutes0 you should see
each cap charge and discharge as you put the meter across it, then
reverse it, and reverse it again. They should all act about the
same. One that doesn't give much meter action is the bad one.
73,
Jim K9YC
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