>
>henry gillow-wiles wrote:
>> Now, the amp goes into an hard fault, indicating a problem with the HV
>> section, at random intervals. The transformer is tapped at 200 volts and
>> the line voltage runs from 210 to 225 volts.
>> Any ideas?
>> Henry
>> KB7RTA
>> henry@pacinfo.com
>
>I would change the transformer primary tap to 220 volts. My guess is
>that by having it set at 200 when you are actually getting 225 produces
>a much higher voltage on the secondary than the protection circuitry of
>the amp is designed for. So when your line voltage occasionally hits
>the 225 level, clunk, out goes the 89 with a HV fault.
Is the 89's protection circuitry designed to trip at c. 10% over-voltage
from the HV supply? At this point, it might be useful to check the
3cx800a7s with a high-pot to see if they have leakage from loose gold
particles. If a high-pot is not available, operating the amplifier with
the hv on and the tubes removed would help to isolate the prob. area --
i.e., if no hv fault occurs with the tubes removed, the fault is In the
tubes.
- later, Ken
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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