Table 12-2. TAM Tests versus Test Connectors
Connector Manual Probe Troubleshooting Test Measured Signal Lines
A14J16 YTF Offset DAC
MS6
YTF Gain and Offset Input
MS2
YTF Gain DAC
MS1
YTF Drive
MS3
Band Switch Driver
MS8
A14J17 Main Coil Coarse DAC
MS3
A14J18 LODA Drive MS5, MS6, MS7, MS8
A14J19 Second Conv PIN Switch
MS8
Second Conv Mixer Bias
MS1
Second Conv Drain Bias MS3
Second Conv Doubler Bias
MS4
Second Conv Driver Bias
MS5
First Mixer Drive Switch
MS7
First Mixer Drive DAC
MS6
A14J302 Revision MS7
A15J400 IF AMP/Limiter Bias MS6
A15J502 Third LO Tune Voltage
MS3
3rd LO Driver Amp
MSl,
MS8
A15J602 SIG ID Collector Bias
MS7
RF Gain Control Test
MSl,
MS3
A15J901 Revision
MS3
External Mixer Switch
MSl,
MS8
Signal ID Switch MS5, MS6
External Mixer Bias
MS7
Low Band Problems
1. Disconnect all inputs from the front-panel INPUT
50R
connector.
2. Set the HP 85623 to the following settings:
Center frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 Hz
Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
..lMHz
Input attenuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 dB
3. The LO feedthrough amplitude observed on the display should be between -6 and
-30
dBm.
Note
The marker will not PEAK SEARCH on the LO Feedthrough when in a
non-zero span. To measure the LO Feedthrough amplitude with the markers,
set the SPAN to 0 Hz and CENTER
FWQ
to 0 Hz. Press
(MKRI
ON.
4. If the LO feedthrough amplitude is within limits, but signals are low, the RF path
following the A8 mixer is probably operating properly.
12-4 RF Section