AW: [Elecraft] K2 - VCO-Test (Alignment an d Test, Part II)

[David Broger]

Hi Bob

>K15 pins 2 and 3 = 0 ohms (continuity )

ok

>K14 pins 3 and 4 = 0 ohms

ok

>K13 pins 7 and 8 = 0 ohms

ok

>Also there should be zero ohms when measuring from K13 pin 8 to K15 pin 3
and also from K13
>pin 8
>to Terminal #2 of T5.  These points are all connected through the relays
when the band is 40m.

it's 0.3 ohm -> ok

>The capacitors involved are C70, C71 and C73. These must be the correct
values and properly
>soldered.

c70 ?? sorry but I haven't a c70 and Ican't find it in the part list!! I
have a board rev b. Is it possible that this board hasn't c70?
c71 is "820" -> ok
c73 is "470" -> ok

>DC voltage checks (use the resistor to isolate the probe):
>U3 pin 3 = 4.0V +/- 0.5V
>U3 pin 2 = U3 pin 3 +/- 0.1V
>U3 pin 6 = U3 pin 3 +/- 0.1V

all ok

This assures the buffer amp U3 is properly biased. This should apply even
when the PLL is not working.

>Check the bias current on the oscillator Q18 by measuring the voltage
across R15 (33 ohms).
>Put the red probe on one end of R15 and
>the black probe on the other end (it doesn't matter if the reading is
negative or positive).
>This should be around 0.05 to 0.3 Volts. Indicating a bias current of 1 to
10 mils.  That's a >broad range but we're just looking for
>a very rough value now which indicates that Q18 is operating with some
reasonable level of
>bias current.

it's only 0.017 volts. It seems to bee too low. But when I tip (not
pressing!) with a screw-driver (with a insulator is no! effect) on terminal
2 of t5 it goes up to 0.044 volts. When I touch t5 with a wet finger, the
voltage goes up to 0.067 volts!!!

>The Source voltage of Q18 should be around 1 to 3 volts.

it's 1.1 volts



73 de David