[Elecraft] Be careful installing the ALC mod

[Don Brown]

HI

I installed the 10/12 BPF and ALC mod in a K2 I am building and I could n=
ot get 15 meters to tune up. Even though I could get full power on 30 and=
 10 the slugs did not set where I had remembered in other K2's I have bui=
lt. 30 was too low and 10 was almost to the top of the can 15 did not wor=
k at all. =20

One weird symptom was 15 would tune up if I turned off the radio while on=
 15 and then turn it back on. But if I changed bands and back to 15 it wo=
uld not work. After spending some time troubleshooting the BPF circuit ch=
ecking the relays and running up other blind alleys. I finally noticed I =
had connected the 1n4148 diode to the wrong side of where C76 would be in=
stalled (this cap is not normally installed and the ground side is where =
the diode should connect). Moving it to the correct pad solved all of the=
 problems. =20

I would have been suspicious of the mod if the radio had worked and the p=
roblems showed up after the mod install. But this was a new radio and I i=
nstalled the mod during the build so the radio had not been aligned befor=
e. =20

Look at the drawing very carefully and make sure you understand where to =
install the diode. I had done this mod 3 times before but I still got it =
wrong this time. =20

On the bright side I learned a few things about the BPF circuit and how t=
he switching of the relays work.

Don Brown
KD5NDB


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