Table 10-l 1. Amplifier Polarities

 

 

YTO Error

VCO Sweep

ERRSGN

VCOSGN

 

 

Sign Amplifier

Driver

(A14U313 p i n

(A14U425 p i n

 

 

 

Amplifier

12)

12)

oller’s Offset

Positive

Positive

Negative

TTL

TTL

 

 

 

 

High

Low

Oscillator

Sampler IF

 

 

 

 

Swept

 

 

 

 

 

 

Negative

Negative

Negative

TTL Low

TTL High

 

Sampler IF

 

 

 

 

 

 

 

 

 

 

Roller’s Main

Positive

Positive

Positive

TTL High

TTL

 

 

 

 

 

High

Oscillator

Sampler IF

 

 

 

 

Swept

 

 

 

 

 

 

Negative

Negative

Negative

TTL Low

TTL Low

 

Sampler IF

 

 

 

 

 

 

 

 

 

 

FM/Main

Positive

Positive

Does not apply

TTL High

Does not apply

Y T O

Sampler IF

 

 

 

 

Coils Swept

 

 

 

 

 

 

Negative

Negative

Does not apply

TTL Low

Does not

 

 

 

 

 

apply

 

Sampler IF

 

 

 

 

 

 

 

 

 

 

Troubleshooting an Unlocked YTO PLL

1.If the YTO PLL is unlocked, error code 301 should be displayed. Place the HP 8560A in ZERO SPAN. Figure 10-8 illustrates the simplified YTO PLL.

2.Move the jumper on A14523 to connect pins 2 and 3 (TEST position). Refer to Figure 10-3 for the location of A14523. Error code 301 should no longer be displayed. (The YTO PLL’s feedback path is now open.)

3.On the HP 8560A, press (CAL), MORE, FREQ DIAGNOSE, and LO FREQ . The displayed LO FREQ is the desired YTO frequency. Record the YTO’s calculated frequency below:

YTO Frequency (calculated) =

 

MHz

 

Synthesizer Section lo-25