Hello all,
Have just completed the K2DSP and all appears to to work FB, except for a
loud pop on power up. The troubleshooting section of the manual indicates
that this may be down to a problem with the mute circuitry.
As an initial check, went through the voltage chart and compared my results,
with the following differences (manual value in brackets)
U1-5 = 5v (0v)
U1-14 = 0v (5v)
U1-15 through U1-19 = 5v (0v)
D3-C = 5v (0v)
The interesting difference is U1-14 which I believe is the MUTE output from
U1 and which according to the manual should be at 5v but I have 0v. If
however pin 14 was at 5v then looking at the diagram Q7 would be turned on,
yet the table has voltages showing Q7 is off. Have I got this wrong, or is
the manual incorrect? Why do other pins have different voltages to the
manual, even though the DSP functions all appear to be working OK?
The other active part of the mute circuitry is the pair of FETs Q5 & Q6, and
I am a bit concerned that one or both of these may be damaged. During the
install, it is not until page 10 when it states that Q5 & Q6 are sensitive
to static. In all the previous Elecraft builds I've done, if any transistors
were static sensitive, they were put into the conductive foam along with the
ICs, but in my KDSP2 package they were just loose in the bag with the bulk
of the rest of the components. As a consequence,I never thought to take any
special anti-static precautions hadling these during the inventory check. Is
there a quick way of checking their fuctionality before ordering
replacements?
Any help would be much appreciated.
73, Don
M1DIC
K2/100 #3082
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