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Dave M[_3_] Dave M[_3_] is offline
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Default Heathkit SB-1000 problem

Christopher Hall wrote:
I am the second owner of a Heathkit SB-1000 that was built in the late
1980s. It was working great until I accidentally tried to tune it
into a mistuned antenna and I saw a flash through the ventilation
screen on the left side somewhere around the rectifier/filter section
and there is now no power output. The amp powers up, the fan runs,
the meter lamps light and the tube lights up. The amps multimeter
shows 3400 volts on the high voltage position (a little high maybe
but it has always been like that). With no drive, when the amp is
keyed there is no plate current and no grid current. Keyed with drive
there is grid current, but no plate current and no power output.
These conditions are the same regardless of which band the amp is set
to. I had thought that the zener diode might have failed so I
replaced it, but nothing has changed. I would appreciate any thoughts
as to what may be the problem and how to fix it.
73
Chris
VE9ZX



The first thing to check is to see if HV is present on the plate of the
final. If not, there's something blown open, likely in the HV rectifier
circuit. Check rectifiers and capacitors on the HV rectifier and HV filter
boards. Also, make sure there's continuity from the HV rectifier to the
plate of the final. An open circuit there means an open resistor or
inductor between the plate and HV rectifier/filter.

Cheers,
--
David
dgminala at mediacombb dot net