Mick,
I might believe 3.75 volts or above may be OK, but if you have run out of
adjustment range at 3.3 volts, something is wrong.
First, check the voltage out of your 8 volt regulator (Control Board U4).
If it is OK, look at the schematic for the Control Board (lower left corner)
to identify the resistors associated with the AGC Threshold pot - check the
value of RP6 and check the soldering carefully. The RF Gain and the AGC
Threshold pot and the other resistors (RP6 and the pot R1) form a
three-legged voltage divider with 8 volts applied to one leg (the RF Gain
control should show zero ohms in its full CW position), so if the resistor
values are correct and the 8 volt supply is correct, you should have no
problem adjusting to 3.8 volts with the AGC Threshold pot near max, and
about 2.6 volts at the other end of rotation. Be certain that R1 is
actually a 50k pot (measure directly across its terminals when adjusted for
max resistance). There is nothing else in the circuit to cause problems.
73,
Don W3FPR
> -----Original Message-----
>
> Hi all
> I have just finished alignment and test part 1 all is good
> except the test for setting the AGC threshold when I adjust R1
> i can only get a max voltage of 3.30v is this ok ?.
>
> Thanks Mick M1MGD..
>
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