Quote:
Originally Posted by 3pinplug
Hi Peter
Is there a specific way of confirming if the channel spacing knob is fitted in the correct position?
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Look at the front panel switch diagram.
For each switch position tabulate the expected logic V The actual logic. Look for patterns that match.
If you loosen the nut behind the cap on the knob, the knob becomes free turning on the shaft, and can be locked anywhere.
The channel knob is the only switch without end-stops if I recall correctly so you cant use the end stops to position it.
Another tip...Dont use a meter to measure the logic levels in digital circuits. Use your oscilloscope.
The logic could be switching very fast or oscillating and a meter may give an RMS or averaged value. The 4.13V on IC6 pin 11; is it 4.13VDC, or a 12V pulsed output with a duty cycle of 1:3?
I tend to use my oscilloscope for most testing (digital and analogue), and the DMM's for when I need to make an accurate measurement.
Edit
Another way to check the position of the knob on the channel spacing switch is to check the pulses released by the logic board pin 18 match the specified number of pulses shown in the manual. A digital storage scope, logic analyser, or frequency counter with pulse counting will make this easy as you need to count up to 64 pulses for each operation of the step switch.
remember the speed switch MUST be in slow position for all testing...