[frsimen]

35kHz might be correct if you have the fine tune control switched to INT. If you switch it to OFF you should be measuring 37.5kHz.

Certainly, there is nothing now on the logic board that can be causing the out of range signal to be generated.

From the block diagram, there are only four signals passing from the logic board to the divider /phase assembly:
Up/Down Pin 16
Pulse Pin 15
Special Channel Select Pin 4
37.5kHz pulse. Pin 18

Of the above, only the Up/Down and pulse feed into the N counter, formed from IC4, 7, 20, 13 and 23. These 5 ICs make an 18 bit counter.

The states of the 8 most significant outputs are used to address the ROM IC16, which provides the out of band control along with an additional feed from the bandswitch which indicates when the 5-32MHz band has been selected. The output of the ROM is fed via a multiplexer, IC11 before driving the step up/step down circuit. The multiplexer output will be enabled/disabled by a clock signal from IC19.

When first switched on, the counter should initialise to values which have been programmed in to each IC via their ABCD inputs (by connecting them to either 0V or 12V). This relies on a pulse, generated by C11/R33, being fed into pin 1 of all five ICs to allow them to set up properly.

If there are no pulses coming in on pin 15, the counter should stick to the pre-programmed values if it is working correctly. Those values are what makes a working generator start up somewhere near the mid frequency of the selected range. When pulses are received on pin 15, they will increment or decrement the output of the counter, depending on the state of the Up/Down control line.

The counter output is then used to program the divide by 160/161 and the divide by N counter at the top of the phase detector circuit, which divides the VCO frequency down to feed to the phase detector.

The out of range logic is operating, which suggests that the output of the N counter (IC4, 7 etc) is not in the range that it is expected. The frequency display confirms that the output frequency is being commanded higher than it should be. The out of range signal will appear to pulse on and off all the time the count is out of range due to the clock feed from IC19.

It would appear that there is a problem in the N counter circuit, so the following should be checked, with the input to pin 15 on the phase detector board connected. Leave the connection to pin 15 on the logic board disconnected to stop the constant stream of pulses from the out of range down pulse circuit.

Check that 12V is present on pin 16 of ICs 4, 7, 20, 13 and 23.

Switch off and check for continuity from the junction of C11 and R33 to pin 1 of ICs 4, 7, 20, 13 and 23.

Connect the oscilloscope probe to pin 1 of IC4. Switch the generator on and confirm that a short 12V pulse is seen. It should back drop to 0V.

Check that there is no sign of a pulse waveform on pin 7 of the IC 4,7 20,13 and 23.

Check the outputs which feed the address lines of the ROM, IC16 as follows:

IC23 check pin 6 - it should be at 12V, pin 11 should be at 0V.

IC13 Pin 6, 11 and 14 should be at 0V, pin 2 should be at 12V.

IC20 Pins 2 and 9 should be at 0V.

The other pins don't feed directly into the ROM circuit, so won't cause the out of range signal to be generated. Check the soldering of any ICs which don't have the correct output, particularly the A, B, C and D input pins.

Hopefully, one of the tests above should reveal the culprit.

Paula