Hello! I have just built my second K8064 dimmer (first one was successful).
This time, on running the test and adjustment procedure, the self test appears to operate correctly, LD1 & LD2 flashing together briefly and then LD1 flashing once (UK mains frequency 50Hz). At this point the 40Watt tungsten lamp that I have connected comes on full, even though the control voltage is at zero. Adjustment of RV1 and RV2 have no effect.
The voltage of pin 4 on IC2 is 4.41V and stays there whatever. Pin 5 is at 5.05V.
Pin 6 is at 2.9V with RV1 fully counterclockwise and RV2 fully clockwise, and is at 3.53V with RV1 fully clockwise and RV2 fully counterclockwise.
The voltage on pin 9 of IC1 (analog) is also at 4.41V, implying no current in R19 and transistor in IC1 turned off.
Varying the DC control voltage has no effect. The voltage between pins 1 and 2 on IC2 vary from 0V with 0V input to 1.116V with 12 V input.
Perhaps a faulty IC2 with no opto coupling?
I’d really appreciate suggestions on how to fix this problem!
UPDATE: Problem solved - small solder track bridge (Doh!)