Connex CX-3300HP low VCO voltage

[Hawkeye351]

Got a Connex CX-3300HP on the desk today with low VCO voltage.

Cannot get the VCO voltage up to 3.20v. it'll go up to 2.19v and then drop out or start dropping back down.

Issue with radio is, frequencies are all out of whack.

10.2398mhz measured on pin 4 of the PLL.
15.23??mhz measured at TP3
Checked wires going to channel encoder, all are firm and making good connection. Checked all other connections to main board and band control, all show good connections. Checked 8v regulator, getting proper voltages, checked audio IC, getting proper voltages, checked for PLL voltage, it's present at 8.56v. Solder joints look good under zoomed in camera.

What would prevent the VCO from being able to reach 3.20v?

 

[nomadradio]

Umm, what's the power supply voltage to the chip on pin 1? Should be 8 or 9 Volts DC.

Might be that simple.

73

 

[Hawkeye351]

Umm, what's the power supply voltage to the chip on pin 1? Should be 8 or 9 Volts DC.

Might be that simple.

73

8.56v

 

[nomadradio]

The amplitude of the difference frequency (VCO minus 14.01 crystal) feeding pin 2 of the PLL can cause twitchy issues if the amplitude is too low. Should be at least 1 Volt peak-to-peak, more typically 2 to 3 Volts.

73