>Continuing this thread...
>
>In addition to the bad resister inside the meter, the two 1.5 ohm grid
>resistors were open (thanks to W1QJ for encouraging me to check those too).
>
** A suddenly open grid-current meter shunt resistor indicates a burst
of grid current. Are there glitch-protection diodes across the meter
movements? Have you measured the full scale meter I-sensitivity?
>Several weeks back I posted my AL-1200 story - I was using it on 40meters
>during a contest when it arced. The IC756ProII connected to it went south -
> the transmitter no longer put out any RF. ICOM has it, they say some
>protective diodes were taken out.
>
>Earlier, I discovered that the resistor in the parasitic suppresser came
>unsoldered. Is it a reasonable theory that the parasitic suppresser failed
>causing some self-oscillation and excessive grid current that took out the
>grid resistors (and my 756proII)? Or should I be looking for a different
>underlaying cause?
** What is the measured resistance of the suppressor resistor that
became unsoldered?
>
>I'll be picking up some new grid resistors and taking it from there.
>
> Dana
>
>
>
>Dana Roode wrote:
>> Amps folks -
>>
>> Ok, I removed the tube and the meter still went negative. I checked the
>> filament connections with the tube out, nothing is shorted to ground.
>>
>> I was suspect of the metering circuit itself. The left multi-function
>> meter measured 300 ohms across the terminals, the right grid meter
>> measured 15k. The parts list indicates both meters are 300 ohm 1ma.
>>
>> I took the grid meter apart, it has a component (a precision resister, I
>> assume) in series with each internal meter movement lead. One measured
>> 100 ohms, the other about 15k.
>>
>> I am pretty clueless about this, and Im at a loss as to why a 100ohm
>> resister would become 15k, but perhaps this is my problem.
>>
>> Dana
>>
>>
>> Dana Roode wrote:
>>
>>> What does it mean when you power up an AL-1200 and the grid current
>>> meter pins negative (no drive power supplied)?
>>>
>>> Dana
>>>
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>>>
>>
>>
>
>
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