Troubleshooting Charts: RX RF

9-21

 

 

 

RX RF—Page 2

1

Measure 2nd LO at

TP501 on PCB side 2

Signal No

Present?

Yes

LO Freq.

OK?No 3

UHF: 71.1 MHz

Yes

Measure

RXCK, P1-5

RXFS, P1-6

RXDO, P1-12

Observe

0 to 3 Vdc

digital signals

Levels No

OK? 5

Yes

Measure

bit clock rate

(Fbit) at RXCK

Fbit =

No

4

1.2 MHz?

 

 

 

 

Yes

 

 

 

 

 

RXFS = 20 kHz

 

 

sync pulse

 

 

 

 

No

 

 

 

 

 

RXFS

 

5

OK?

 

 

 

Yes

2nd LO DC bias

 

Q501-c

No

Check Voltage

= 5.0 Vdc?

 

Regulator U1

 

Yes

No

Replace

 

Q501-e

= 3.7 Vdc?

 

Q501

Yes

Remove SH501

and inspect

2nd LO VCO

Visual No Repair

examination Defects OK?

Yes

Replace

Q502

RXDO = 24-bit I,

24-bit Q, 8-bit

AGC. AGC varies

with RF level

RXDO No

OK? 5

Yes

Go to

VOCON RX

AUDIO flowchart

MAEPF-27471-B

6881094C12-A

November 11, 2004

Page 125
Image 125
Motorola SSETM 5000 service manual Vocon RX