I do factory authorized repair on the Logikit SCAF-1 Filter. This service is available for factory assembled and kit built units. Please contact me via Email for rates and shipping instructions.

On the factory assembled units the 1/8" jack is wired for earphone output and the 1/4" jack is wired for speaker output. Both jacks are wired for stereo plugs. If you want to use a mono plug you must cut the jumper between the tip and ring connections. If you do not cut the jumper the mono plug will short out the SCAF-1 output. You can use a wire cutter to cut the jumper between the tip and ring connections. On the phone jack this is a small bare wire, on the speaker jack it is a red wire. If you want to swap the speaker and earphone jacks you can easily do so.  Examine the connections on the two jacks.  If there is a green wire connected to each jack and no 100 ohm resistor connected between them just swap the green wires on the two jacks. If there is just one green wire and a 100 ohm resistor connected between the two jacks move the green wire to the tip connection on the jack that you want to be the speaker output.  Verify that the 100 ohm resistor is connected between the tip connections on the two jacks.  This resistor provides the earphone output from the speaker output.  If you do not feel comfortable doing any of these changes I will do them for you if you pay shipping both ways.

Ron, K0QVF

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If your filter does not work properly after assembly it may be helpful to have someone else check your work. If all parts and connections look OK remove the chips from their sockets and go over the solder joints on the circuit card with your soldering iron. Sometimes a connection may look good but may be open.

Verify that there is a minimum of 12 volts between the red and ground wires on the power input jack when the SCAF-1 is turned on.

Here are some voltage checks that you can make. All readings should be within + or - 0.5 volts.

Reference the following to internal signal ground which you can find on U1 pin 6.

IC	Pin	Voltage
U1	7	+4.5
U1	2	-4.6
U1	5	0
U2	7	+4.5
U2	2	-4.6
U2	5	0
U3	7	+4.9
U3	4	-5.0
U3	6	0
U3	3	0
U4	7	+4.9
U4	4	-5.0
U4	6	0
U4	3	0
U5	4	+4.9
U5	8	+4.9
U5	1	0

Reference the following to power ground.

IC	Pin	Voltage
U6	2	0
U6	4	0
U6	6	Power input voltage minus 0.7V
U6	5	One half of the reading at U6 pin 6

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If these voltages are normal then we need to trace the signal to see were it is getting lost. Set R17 and R27 to mid-range. Connect the filter to your radio and get a good signal with it switched out. Switch the filter in and turn the knob fully clockwise. Using an oscilloscope check the signal at the points listed below. If you do not have an oscilloscope connect one side of your phones to ground, connect the other side of the phones to one side of a 0.1 uf capacitor. Then connect the free end of the capacitor to the following pins and listen for the signal. The signal should be about the same on all pins except U6 pin 5 which will be stronger. This will tell you were the signal is getting lost.

RCA jack center pin

U1 pin 8

U1 pin 5

U2 pin 8

U2 pin 5

U2 pin 3

U3 pin 6

U4 pin 6

U6 pin 5

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U5 output waveform checks.

The photos below are oscilloscope displays for pin 3 on U5. The horizontal center line is 6 volts. The vertical scale is 2 volts per major division. The horizontal scale is 5 microseconds per major division for CCW and 1 microsecond for CW.