SG-2000 MANUAL
162
The SGC Building, 13737 S.E. 26th St. Bellevue, WA. 98005 USA
©1995, SGC, Inc.
TEL: (206) 746-6310 FAX: (206) 746-6384
Set conditions as follows:
any frequency in 1.6 to 30 MHz range
A3J
+90 dB (32 mV RMS) at RF In
R286 adjusted at approximately mid value
dB meter and scope attached to J301 pin 3
You should then read the following voltages:
TP202 = 4.77 ±.01 V
TP207 = 4.8 ±.1 V
TP302 = 0.16 ±0.005 Vpp
J301 pin 3 = 6.0 Vpp, no clipping
23.1.27
VCO Troubleshooting
1) VCO4, VCO2 and VCO1 failure - frequency is different than the value
expected at TP403 (for VCO4), TP401 (for VCO1), TP402 (for VCO2) and the
voltage at TP603 and TP601 is zero or 8 VDC.
Check the values of components, check for shorts, check for general line
fault conditions along the CLK, DIN and LE lines
2) To check that the PLL works properly, follow the procedure below ( example
given for VCO2):
Attach frequency counter to TP402
Attach scope to TP402
Attach voltmeter to TP602
Turn on the radio and program in the frequency 10.0 MHz, USB.
•
The frequency meter should read 71.64 MHz.
•
The scope should read 3 ±.5 Vpp.
•
The voltmeter should read 5.5 ±0.2 VDC.
If the frequency is different, remove from the circuit one side of R427.