Hi Mike,
I measured from the red wire to ground - got about 2 megohms of
resistance.
Thinking I might be crazy, I hooked up the red wire to a current-limited
bench power supply (negative of the supply to chassis) and once the
voltage applied to the wire gets over about 4 volts, it goes into
current limit.
I'm going to remove the final amp section here shortly and have a look
inside. :)
thanks much and 73,
ben, kd5byb
On 7/14/2012 7:29 AM, Mike Bryce wrote:
Ben,
the finals and the driver transistors are all connected to the +12
volt supply directly. Although a shorted driver would more than
likely smoke before the final transistor simply because the final are
more robust and could take a whale of a lot of current.
That's why the ten ten power supply instantly goes into over current
shut down and the smaller supply goes into current limiting.
There's the possibility that the decoupling capacitors inside the PA
have failed, but that's a real stretch.
did you measure resistance between the red wire going into the PA and
ground?
bet you'll see it very low, a few ohms perhaps..
mike, wb8vge
On Jul 14, 2012, at 8:20 AM, Ben Hall wrote:
Hi Mike!
Got the covers off, unsoldered the red wire going from the final
amp section to the power input board and it powers up fine and I
hear static in the speaker. :) Seems to operate normally - can
switch filters, etc...
I think you've hit the nail on the head! Something is amiss in
the driver / final section.
Interestingly, measuring from the disconnected red wire to ground
and to the negative power supply input shows high resistance. Not
sure what to make of that. The thought that maybe the finals are
okay and the driver is shorted (only shorting the finals when power
is applied) did occur to me, but without a schematic I'm just
guessing.
Anyone have a schematic, service manual, or parts list for a
Paragon?
thanks much and 73, ben kd5byb
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