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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